1
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Karunarathne SI, Spokevicius AV, Bossinger G, Golz JF. Trees need closure too: Wound-induced secondary vascular tissue regeneration. Plant Sci 2024; 339:111950. [PMID: 38070652 DOI: 10.1016/j.plantsci.2023.111950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Revised: 11/03/2023] [Accepted: 12/05/2023] [Indexed: 01/13/2024]
Abstract
Trees play a pivotal role in terrestrial ecosystems as well as being an important natural resource. These attributes are primarily associated with the capacity of trees to continuously produce woody tissue from the vascular cambium, a ring of stem cells located just beneath the bark. Long-lived trees are exposed to a myriad of biological and environmental stresses that may result in wounding, leading to a loss of bark and the underlying vascular cambium. This affects both wood formation and the quality of timber arising from the tree. In addition, the exposed wound site is a potential entry point for pathogens that cause disease. In response to wounding, trees have the capacity to regenerate lost or damaged tissues at this site. Investigating gene expression changes associated with different stages of wound healing reveals complex and dynamic changes in the activity of transcription factors, signalling pathways and hormone responses. In this review we summarise these data and discuss how they relate to our current understanding of vascular cambium formation and xylem differentiation during secondary growth. Based on this analysis, a model for wound healing that provides the conceptual foundations for future studies aimed at understanding this intriguing process is proposed.
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Affiliation(s)
- Sachinthani I Karunarathne
- School of Agriculture, Food and Ecosystem Sciences, University of Melbourne, Parkville, VIC 3010, Australia
| | - Antanas V Spokevicius
- School of Agriculture, Food and Ecosystem Sciences, University of Melbourne, Parkville, VIC 3010, Australia
| | - Gerd Bossinger
- School of Agriculture, Food and Ecosystem Sciences, University of Melbourne, Parkville, VIC 3010, Australia
| | - John F Golz
- School of BioSciences, University of Melbourne, Parkville, VIC 3010, Australia.
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2
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Robledo J, Welker S, Shtein I, Bernardini C, Vincent C, Levy A. Phloem and Xylem Responses Are Both Implicated in Huanglongbing Tolerance of Sugar Belle. Phytopathology 2024; 114:441-453. [PMID: 37551959 DOI: 10.1094/phyto-05-23-0148-r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/09/2023]
Abstract
Although huanglongbing (HLB) is a devastating citrus disease, improved tolerant cultivars, such as Sugar Belle (SB) mandarin, have been identified. To understand the responses that HLB-affected SB undergoes, we compared 14CO2 fixation, carbohydrate export, phloem callose accumulation, relative expression of plant defense activators, and anatomical changes between healthy and infected SB trees versus susceptible Pineapple (PA) sweet orange. Eight- to ten-week-old leaves of infected SB showed a 2.5-fold increase in 14CO2 fixation and a 13% decrease in 14C-carbohydrate export, whereas HLB-affected PA presented a decrease of 33 and 50%, respectively. The mean distance of a callose deposit to its closest neighbor was 36% smaller in infected SB versus healthy, whereas in HLB-affected PA, it was 33% higher. Expression of papain-like cysteine proteases (PLCPs) was upregulated in SB but downregulated in PA. Infected SB showed minor alterations in the number of xylem vessels, a 16% larger xylem vessel lumen area, and a 14% increase in the proportional area of the xylem. In contrast, PA showed a 2.4-fold increase in the xylem vessel number and a 2% increase in the proportional xylem area. Three complementary mechanisms of tolerance in SB are hypothesized: (i) increased carbohydrate availability induced by greater CO2 fixation, mild effect in carbohydrate export, and local accumulation of callose in the phloem; (ii) activation of defense response via upregulation of PLCPs, and (iii) increased investment in the xylem structure. Thus, phloem and xylem modifications seem to be involved in SB tolerance.
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Affiliation(s)
- Jacobo Robledo
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, U.S.A
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611, U.S.A
| | - Stacy Welker
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, U.S.A
| | - Ilana Shtein
- Eastern Region Research and Development Center, Ariel, Israel
| | - Chiara Bernardini
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, U.S.A
| | - Christopher Vincent
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, U.S.A
- Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, U.S.A
| | - Amit Levy
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, U.S.A
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611, U.S.A
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3
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Gersony JT, Holbrook NM. Phloem turgor is maintained during severe drought in Ricinus communis. Plant Cell Environ 2022; 45:2898-2905. [PMID: 35854434 DOI: 10.1111/pce.14401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 07/13/2022] [Accepted: 07/15/2022] [Indexed: 06/15/2023]
Abstract
The phloem is a key player in whole plant functioning-transporting carbon from sites of production to sites of demand-and is likely influenced by drought due to its dependence on water for generating pressure-driven bulk flow transport. Yet, phloem functioning during drought remains largely unknown due to a lack of experimental studies. Here, we use a phloem-bleeding species, Ricinus communis, to investigate phloem loss-of-function in the context of leaf physiological processes, the mechanisms of phloem turgor maintenance during drought, and the role of turgor in phloem loss-of-function. We found that the solute concentration in the phloem sap doubled over the drought, which allowed phloem turgor to be maintained past the point at which leaves have reached permanent stomatal closure. We also found that phloem turgor did not decline before bleeding ceased, which suggests that phloem bleeding ceassation (interpreted as the cessation of transport) occurred when the phloem still had turgor. In sum, our findings highlight the robustness of phloem functioning, with important implications for forecasting whole-plant carbon dynamics and drought-induced tree mortality.
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Affiliation(s)
- Jess Toby Gersony
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA
- Department of Natural Resources and the Environment, University of New Hampshire, Durham, New Hampshire, USA
- Department of Biological Sciences, Smith College, Northampton, Massachusetts, USA
| | - Noel M Holbrook
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA
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4
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Nakad M, Domec JC, Sevanto S, Katul G. Radial-axial transport coordination enhances sugar translocation in the phloem vasculature of plants. Plant Physiol 2022; 189:2061-2071. [PMID: 35588257 PMCID: PMC9343002 DOI: 10.1093/plphys/kiac231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Accepted: 04/27/2022] [Indexed: 05/21/2023]
Abstract
Understanding mass transport of photosynthates in the phloem of plants is necessary for predicting plant carbon allocation, productivity, and responses to water and thermal stress. Several hypotheses about optimization of phloem structure and function and limitations of phloem transport under drought have been proposed and tested with models and anatomical data. However, the true impact of radial water exchange of phloem conduits with their surroundings on mass transport of photosynthates has not been addressed. Here, the physics of the Munch mechanism of sugar transport is re-evaluated to include local variations in viscosity resulting from the radial water exchange in two dimensions (axial and radial) using transient flow simulations. Model results show an increase in radial water exchange due to a decrease in sap viscosity leading to increased sugar front speed and axial mass transport across a wide range of phloem conduit lengths. This increase is around 40% for active loaders (e.g. crops) and around 20% for passive loaders (e.g. trees). Thus, sugar transport operates more efficiently than predicted by previous models that ignore these two effects. A faster front speed leads to higher phloem resiliency under drought because more sugar can be transported with a smaller pressure gradient.
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Affiliation(s)
| | - Jean-Christophe Domec
- Bordeaux Sciences Agro, UMR 1391 INRA-ISPA, Gradignan 33175, France
- Nicholas School of the Environment, Duke University, Durham, North Carolina 27708, USA
| | - Sanna Sevanto
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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5
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Twayana M, Girija AM, Mohan V, Shah J. Phloem: At the center of action in plant defense against aphids. J Plant Physiol 2022; 273:153695. [PMID: 35468314 DOI: 10.1016/j.jplph.2022.153695] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 04/04/2022] [Accepted: 04/08/2022] [Indexed: 06/14/2023]
Abstract
The location of the phloem deep inside the plant, the high hydrostatic pressure in the phloem, and the composition of phloem sap, which is rich in sugar with a high C:N ratio, allows phloem sap feeding insects to occupy a unique ecological niche. The anatomy and physiology of aphids, a large group of phytophagous insects that use their mouthparts, which are modified into stylets, to consume large amounts of phloem sap, has allowed aphids to successfully exploit this niche, however, to the detriment of agriculture and horticulture. The ability to reproduce asexually, a short generation time, the development of resistance to commonly used insecticides, and their ability to vector viral diseases makes aphids among the most damaging pests of plants. Here we review how plants utilize their ability to occlude sieve elements and accumulate antibiotic and antinutritive factors in the phloem sap to limit aphid infestation. In addition, we summarize progress on understanding how plants perceive aphids to activate defenses in the phloem.
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Affiliation(s)
- Moon Twayana
- Department of Biological Sciences and BioDiscovery Institute, University of North Texas, Denton, TX, 76210, USA.
| | - Anil M Girija
- Department of Biological Sciences and BioDiscovery Institute, University of North Texas, Denton, TX, 76210, USA.
| | - Vijee Mohan
- Department of Biological Sciences and BioDiscovery Institute, University of North Texas, Denton, TX, 76210, USA.
| | - Jyoti Shah
- Department of Biological Sciences and BioDiscovery Institute, University of North Texas, Denton, TX, 76210, USA.
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6
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Lu X, Qin C, Cai J, Zhang M, Yu L, Li J, Wu Q. Study on the selectivity and phloem mobility of Fenoxaprop-P amino acid ester conjugates on rice and barnyard grass. Pestic Biochem Physiol 2022; 183:105086. [PMID: 35430076 DOI: 10.1016/j.pestbp.2022.105086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 03/14/2022] [Accepted: 03/22/2022] [Indexed: 06/14/2023]
Abstract
To improve the selectivity of the fenoxaprop herbicide to rice and barnyard grass, a series of fenoxaprop-P-ethyl-amino acid ester conjugates were designed and synthesized, and tested for biological activity as well as their phloem mobility. The bioassay results indicated that the target compounds possessed better activity against barnyard grass (Echinochloa crusgalli) than rape (Brassica campestris L.) at the concentration of 0.5 mmol/L. Compounds 3h and 3i, showed more than 70% control efficiency against barnyard grass, while less than 30% for rape. The compounds showed less impact on rice after spray treatment than in the germination test. Compounds 3i, 3j, and 3k showed excellently herbicidal activities against barnyard grass and low phytotoxicity to rice. Compound 3k showed 6.1% phytotoxicity to rice at a spray concentration of 0.25 mmol/L, better than fenoxaprop-P-ethyl (61.6%) at the same concentration. The selectivity results of the target compounds revealed that most of compounds obviously reduced phytotoxicity to rice while retaining herbicidal activity of barnyard grass. The herbicidal activity of compound 3d compared to FPE was increased by 50%, while its safety on rice was also increased by 50%. The concentration of the compounds in barnyard grass roots was higher than in rice roots, showing greater phloem mobility. In particular, the concentration of compound 3d on barnyard grass exhibited 142.72 mg/kg which was 3 times as much as Fenoxaprop, while its concentration on rice exhibited 3.65 mg/kg, the results revealed that the difference of phloem mobility might be the important reason for causing the selectivity.
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Affiliation(s)
- Xingliang Lu
- School of Agriculture, Yangtze University, Jingmi Road 88, Jingzhou 434025, China
| | - Chuan Qin
- School of Agriculture, Yangtze University, Jingmi Road 88, Jingzhou 434025, China
| | - Jinlong Cai
- School of Agriculture, Yangtze University, Jingmi Road 88, Jingzhou 434025, China
| | - Min Zhang
- School of Agriculture, Yangtze University, Jingmi Road 88, Jingzhou 434025, China
| | - Linhua Yu
- School of Agriculture, Yangtze University, Jingmi Road 88, Jingzhou 434025, China
| | - Junkai Li
- School of Agriculture, Yangtze University, Jingmi Road 88, Jingzhou 434025, China; Institute of Pesticides, Yangtze University, Jingmi Road 88, Jingzhou 434025, China
| | - Qinglai Wu
- School of Agriculture, Yangtze University, Jingmi Road 88, Jingzhou 434025, China; Institute of Pesticides, Yangtze University, Jingmi Road 88, Jingzhou 434025, China.
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7
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Abstract
The development of secondary vascular tissue enhances the transport capacity and mechanical strength of plant bodies, while contributing a huge proportion of the world's biomass in the form of wood. Cell divisions in the cambium, which constitutes the vascular meristem, provide progenitors from which conductive xylem and phloem are derived. The cambium is a somewhat unusual stem cell population in two respects, making it an interesting subject for developmental research. Firstly, it arises post-germination, and thus represents a model for understanding stem cell initiation beyond embryogenesis. Secondly, xylem and phloem differentiate on opposing sides of cambial stem cells, making them bifacial in nature. Recent discoveries in Arabidopsis thaliana have provided insight into the molecular mechanisms that regulate the initiation, patterning, and maintenance of the cambium. In this review, the roles of intercellular signalling via mobile transcription factors, peptide-receptor modules, and phytohormones are described. Crosstalk between these regulatory pathways is becoming increasingly apparent, yet the underlying mechanisms are not fully understood. Future study of the interaction between multiple independently identified regulators, as well as the functions of their orthologues in trees, will deepen our understanding of radial growth in plants.
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Affiliation(s)
- Emma K Turley
- Department of Biosciences, Durham University, South Road, Durham DH1 3LE, UK
- The Sainsbury Laboratory, Norwich Research Park, Norwich NR4 7UH, UK
| | - J Peter Etchells
- Department of Biosciences, Durham University, South Road, Durham DH1 3LE, UK
- Correspondence:
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8
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Dewar R, Hölttä T, Salmon Y. Exploring optimal stomatal control under alternative hypotheses for the regulation of plant sources and sinks. New Phytol 2022; 233:639-654. [PMID: 34637543 DOI: 10.1111/nph.17795] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 09/19/2021] [Indexed: 06/13/2023]
Abstract
Experimental evidence that nonstomatal limitations to photosynthesis (NSLs) correlate with leaf sugar and/or leaf water status suggests the possibility that stomata adjust to maximise photosynthesis through a trade-off between leaf CO2 supply and NSLs, potentially involving source-sink interactions. However, the mechanisms regulating NSLs and sink strength, as well as their implications for stomatal control, remain uncertain. We used an analytically solvable model to explore optimal stomatal control under alternative hypotheses for source and sink regulation. We assumed that either leaf sugar concentration or leaf water potential regulates NSLs, and that either phloem turgor pressure or phloem sugar concentration regulates sink phloem unloading. All hypotheses led to realistic stomatal responses to light, CO2 and air humidity, including conservative behaviour for the intercellular-to-atmospheric CO2 concentration ratio. Sugar-regulated and water-regulated NSLs are distinguished by the presence/absence of a stomatal closure response to changing sink strength. Turgor-regulated and sugar-regulated phloem unloading are distinguished by the presence/absence of stomatal closure under drought and avoidance/occurrence of negative phloem turgor. Results from girdling and drought experiments on Pinus sylvestris, Betula pendula, Populus tremula and Picea abies saplings are consistent with optimal stomatal control under sugar-regulated NSLs and turgor-regulated unloading. Our analytical results provide a simple representation of stomatal responses to above-ground and below-ground environmental factors and sink activity.
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Affiliation(s)
- Roderick Dewar
- Faculty of Science, Institute for Atmospheric and Earth System Research/Physics, University of Helsinki, PO Box 68, Gustaf Hällströmin katu 2b, Helsinki, 00014, Finland
- Plant Sciences Division, Research School of Biology, The Australian National University, Canberra, ACT, 2601, Australia
| | - Teemu Hölttä
- Faculty of Agriculture and Forestry, Institute for Atmospheric and Earth System Research/Forest Sciences, University of Helsinki, PO Box 27, Latokartanonkaari 7, Helsinki, 00014, Finland
| | - Yann Salmon
- Faculty of Science, Institute for Atmospheric and Earth System Research/Physics, University of Helsinki, PO Box 68, Gustaf Hällströmin katu 2b, Helsinki, 00014, Finland
- Faculty of Agriculture and Forestry, Institute for Atmospheric and Earth System Research/Forest Sciences, University of Helsinki, PO Box 27, Latokartanonkaari 7, Helsinki, 00014, Finland
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9
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Mertens D, Fernández de Bobadilla M, Rusman Q, Bloem J, Douma JC, Poelman EH. Plant defence to sequential attack is adapted to prevalent herbivores. Nat Plants 2021; 7:1347-1353. [PMID: 34650263 DOI: 10.1038/s41477-021-00999-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 08/02/2021] [Indexed: 05/21/2023]
Abstract
Plants have evolved plastic defence strategies to deal with the uncertainty of when, by which species and in which order attack by herbivores will take place1-3. However, the responses to current herbivore attack may come with a cost of compromising resistance to other, later arriving herbivores. Due to antagonistic cross-talk between physiological regulation of plant resistance to phloem-feeding and leaf-chewing herbivores4-8, the feeding guild of the initial herbivore is considered to be the primary factor determining whether resistance to subsequent attack is compromised. We show that, by investigating 90 pairwise insect-herbivore interactions among ten different herbivore species, resistance of the annual plant Brassica nigra to a later arriving herbivore species is not explained by feeding guild of the initial attacker. Instead, the prevalence of herbivore species that arrive on induced plants as approximated by three years of season-long insect community assessments in the field explained cross-resistance. Plants maintained resistance to prevalent herbivores in common patterns of herbivore arrival and compromises in resistance especially occurred for rare patterns of herbivore attack. We conclude that plants tailor induced defence strategies to deal with common patterns of sequential herbivore attack and anticipate arrival of the most prevalent herbivores.
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Affiliation(s)
- Daan Mertens
- Laboratory of Entomology, Wageningen University, Wageningen, the Netherlands
| | | | - Quint Rusman
- Laboratory of Entomology, Wageningen University, Wageningen, the Netherlands
| | - Janneke Bloem
- Laboratory of Entomology, Wageningen University, Wageningen, the Netherlands
| | - Jacob C Douma
- Centre for Crop Systems Analysis, Wageningen University, Wageningen, the Netherlands
| | - Erik H Poelman
- Laboratory of Entomology, Wageningen University, Wageningen, the Netherlands.
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10
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Barceló-Anguiano M, Holbrook NM, Hormaza JI, Losada JM. Changes in ploidy affect vascular allometry and hydraulic function in Mangifera indica trees. Plant J 2021; 108:541-554. [PMID: 34403543 DOI: 10.1111/tpj.15460] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 08/09/2021] [Accepted: 08/11/2021] [Indexed: 06/13/2023]
Abstract
The enucleated vascular elements of the xylem and the phloem offer an excellent system to test the effect of ploidy on plant function because variation in vascular geometry has a direct influence on transport efficiency. However, evaluations of conduit sizes in polyploid plants have remained elusive, most remarkably in woody species. We used a combination of molecular, physiological and microscopy techniques to model the hydraulic resistance between source and sinks in tetraploid and diploid mango trees. Tetraploids exhibited larger chloroplasts, mesophyll cells and stomatal guard cells, resulting in higher leaf elastic modulus and lower dehydration rates, despite the high water potentials of both ploidies in the field. Both the xylem and the phloem displayed a scaling of conduits with ploidy, revealing attenuated hydraulic resistance in tetraploids. Conspicuous wall hygroscopic moieties in the cells involved in transpiration and transport indicate a role in volumetric adjustments as a result of turgor change in both ploidies. In autotetraploids, the enlargement of organelles, cells and tissues, which are critical for water and photoassimilate transport at long distances, point to major physiological novelties associated with whole-genome duplication.
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Affiliation(s)
- Miguel Barceló-Anguiano
- Institute for Mediterranean and Subtropical Horticulture 'La Mayora' - CSIC - UMA, Avda. Dr. Wienberg s/n, Málaga, 29750, Spain
| | - N Michele Holbrook
- Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Avenue, Cambridge, Massachusetts, 02138, USA
| | - José I Hormaza
- Institute for Mediterranean and Subtropical Horticulture 'La Mayora' - CSIC - UMA, Avda. Dr. Wienberg s/n, Málaga, 29750, Spain
| | - Juan M Losada
- Institute for Mediterranean and Subtropical Horticulture 'La Mayora' - CSIC - UMA, Avda. Dr. Wienberg s/n, Málaga, 29750, Spain
- Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Avenue, Cambridge, Massachusetts, 02138, USA
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11
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Zhao J, Ding B, Zhu E, Deng X, Zhang M, Zhang P, Wang L, Dai Y, Xiao S, Zhang C, Liu CJ, Zhang K. Phloem unloading via the apoplastic pathway is essential for shoot distribution of root-synthesized cytokinins. Plant Physiol 2021; 186:2111-2123. [PMID: 33905524 PMCID: PMC8331157 DOI: 10.1093/plphys/kiab188] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 04/15/2021] [Indexed: 05/20/2023]
Abstract
Root-synthesized cytokinins are transported to the shoot and regulate the growth, development, and stress responses of aerial tissues. Previous studies have demonstrated that Arabidopsis (Arabidopsis thaliana) ATP binding cassette (ABC) transporter G family member 14 (AtABCG14) participates in xylem loading of root-synthesized cytokinins. However, the mechanism by which these root-derived cytokinins are distributed in the shoot remains unclear. Here, we revealed that AtABCG14-mediated phloem unloading through the apoplastic pathway is required for the appropriate shoot distribution of root-synthesized cytokinins in Arabidopsis. Wild-type rootstocks grafted to atabcg14 scions successfully restored trans-zeatin xylem loading. However, only low levels of root-synthesized cytokinins and induced shoot signaling were rescued. Reciprocal grafting and tissue-specific genetic complementation demonstrated that AtABCG14 disruption in the shoot considerably increased the retention of root-synthesized cytokinins in the phloem and substantially impaired their distribution in the leaf apoplast. The translocation of root-synthesized cytokinins from the xylem to the phloem and the subsequent unloading from the phloem is required for the shoot distribution and long-distance shootward transport of root-synthesized cytokinins. This study revealed a mechanism by which the phloem regulates systemic signaling of xylem-mediated transport of root-synthesized cytokinins from the root to the shoot.
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Affiliation(s)
- Jiangzhe Zhao
- Institute of Plant Genetics and Developmental Biology, Zhejiang Provincial Key Laboratory of Biotechnology on Specialty Economic Plants, College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua, Zhejiang 321004, P.R. China
| | - Bingli Ding
- Institute of Plant Genetics and Developmental Biology, Zhejiang Provincial Key Laboratory of Biotechnology on Specialty Economic Plants, College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua, Zhejiang 321004, P.R. China
| | - Engao Zhu
- Institute of Plant Genetics and Developmental Biology, Zhejiang Provincial Key Laboratory of Biotechnology on Specialty Economic Plants, College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua, Zhejiang 321004, P.R. China
| | - Xiaojuan Deng
- Institute of Plant Genetics and Developmental Biology, Zhejiang Provincial Key Laboratory of Biotechnology on Specialty Economic Plants, College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua, Zhejiang 321004, P.R. China
| | - Mengyuan Zhang
- Institute of Plant Genetics and Developmental Biology, Zhejiang Provincial Key Laboratory of Biotechnology on Specialty Economic Plants, College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua, Zhejiang 321004, P.R. China
| | - Penghong Zhang
- Institute of Plant Genetics and Developmental Biology, Zhejiang Provincial Key Laboratory of Biotechnology on Specialty Economic Plants, College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua, Zhejiang 321004, P.R. China
| | - Lu Wang
- Institute of Plant Genetics and Developmental Biology, Zhejiang Provincial Key Laboratory of Biotechnology on Specialty Economic Plants, College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua, Zhejiang 321004, P.R. China
| | - Yangshuo Dai
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources, Collaborative Innovation Center of Genetics and Development, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, P.R. China
| | - Shi Xiao
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources, Collaborative Innovation Center of Genetics and Development, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, P.R. China
| | - Cankui Zhang
- Department of Agronomy and Purdue Center for Plant Biology, Purdue University, West Lafayette, Indiana, USA
| | - Chang-Jun Liu
- Biology Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Kewei Zhang
- Institute of Plant Genetics and Developmental Biology, Zhejiang Provincial Key Laboratory of Biotechnology on Specialty Economic Plants, College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua, Zhejiang 321004, P.R. China
- Author for communication:
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12
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Robinson DG, Draguhn A. Plants have neither synapses nor a nervous system. J Plant Physiol 2021; 263:153467. [PMID: 34247030 DOI: 10.1016/j.jplph.2021.153467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Revised: 06/16/2021] [Accepted: 06/22/2021] [Indexed: 06/13/2023]
Abstract
The alleged existence of so-called synapses or equivalent structures in plants provided the basis for the concept of Plant Neurobiology (Baluska et al., 2005; Brenner et al., 2006). More recently, supporters of this controversial theory have even speculated that the phloem acts as a kind of nerve system serving long distance electrical signaling (Mediano et al., 2021; Baluska and Mancuso, 2021). In this review we have critically examined the literature cited by these authors and arrive at a completely different conclusion. Plants do not have any structures resembling animal synapses (neither chemical nor electrical). While they certainly do have complex cell contacts and signaling mechanisms, none of these structures provides a basis for neuronal-like synaptic transmission. Likewise, the phloem is undoubtedly a conduit for the propagation of electrical signaling, but the characteristics of this process are in no way comparable to the events underlying information processing in neuronal networks. This has obvious implications in regard to far-going speculations into the realms of cognition, sentience and consciousness.
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Affiliation(s)
- David G Robinson
- Centre for Organismal Studies, University of Heidelberg, 69120, Heidelberg, Germany.
| | - Andreas Draguhn
- Institute for Physiology and Pathophysiology, Medical Faculty, University of Heidelberg, 69120, Heidelberg, Germany
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13
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Kloth KJ, Shah P, Broekgaarden C, Ström C, Albrectsen BR, Dicke M. SLI1 confers broad-spectrum resistance to phloem-feeding insects. Plant Cell Environ 2021; 44:2765-2776. [PMID: 33837973 PMCID: PMC8360143 DOI: 10.1111/pce.14064] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 03/30/2021] [Accepted: 04/02/2021] [Indexed: 05/13/2023]
Abstract
Resistance (R) genes usually compete in a coevolutionary arms race with reciprocal effectors to confer strain-specific resistance to pathogens or herbivorous insects. Here, we investigate the specificity of SLI1, a recently identified R gene in Arabidopsis that encodes a small heat shock-like protein involved in resistance to Myzus persicae aphids. In a panel with several aphid and whitefly species, SLI1 compromised reproductive rates of three species: the tobacco aphid M. persicae nicotianae, the cabbage aphid Brevicoryne brassicae and the cabbage whitefly Aleyrodes proletella. Electrical penetration graph recording of aphid behaviour, revealed shorter salivations and a 3-to-5-fold increase in phloem feeding on sli1 loss-of-function plants. The mustard aphid Lipaphis erysimi and Bemisia tabaci whitefly were not affected by SLI1. Unlike the other two aphid species, L. erysimi exhibited repetitive salivations preceding successful phloem feeding, indicating a role of salivary effectors in overcoming SLI1-mediated resistance. Microscopic characterization showed that SLI1 proteins localize in the sieve tubes of virtually all above- and below-ground tissues and co-localize with the aphid stylet tip after penetration of the sieve element plasma membrane. These observations reveal an unconventional R gene that escapes the paradigm of strain specificity and confers broad-spectrum quantitative resistance to phloem-feeding insects.
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Affiliation(s)
- Karen J. Kloth
- Laboratory of EntomologyWageningen University & ResearchWageningenThe Netherlands
| | - Parth Shah
- Laboratory of EntomologyWageningen University & ResearchWageningenThe Netherlands
| | | | - Cecilia Ström
- Department of Plant Physiology, Umeå Plant Science CentreUmeå UniversityUmeåSweden
| | | | - Marcel Dicke
- Laboratory of EntomologyWageningen University & ResearchWageningenThe Netherlands
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14
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Pan K, Lu C, Nie P, Hu M, Zhou X, Chen X, Wang W. Predominantly symplastic phloem unloading of photosynthates maintains efficient starch accumulation in the cassava storage roots (Manihot esculenta Crantz). BMC Plant Biol 2021; 21:318. [PMID: 34217217 PMCID: PMC8254309 DOI: 10.1186/s12870-021-03088-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Accepted: 06/08/2021] [Indexed: 06/01/2023]
Abstract
BACKGROUND Cassava (Manihot esculenta Crantz) efficiently accumulates starch in its storage roots. However, how photosynthates are transported from the leaves to the phloem (especially how they are unloaded into parenchymal cells of storage roots) remains unclear. RESULTS Here, we investigated the sucrose unloading pattern and its impact on cassava storage root development using microstructural and physiological analyses, namely, carboxyfluorescein (CF) and C14 isotope tracing. The expression profiling of genes involved in symplastic and apoplastic transport was performed, which included enzyme activity, protein gel blot analysis, and transcriptome sequencing analyses. These finding showed that carbohydrates are transported mainly in the form of sucrose, and more than 54.6% was present in the stem phloem. Sucrose was predominantly unloaded symplastically from the phloem into storage roots; in addition, there was a shift from apoplastic to symplastic unloading accompanied by the onset of root swelling. Statistical data on the microstructures indicated an enrichment of plasmodesmata within sieve, companion, and parenchyma cells in the developing storage roots of a cultivar but not in a wild ancestor. Tracing tests with CF verified the existence of a symplastic channel, and [14C] Suc demonstrated that sucrose could rapidly diffuse into root parenchyma cells from phloem cells. The relatively high expression of genes encoding sucrose synthase and associated proteins appeared in the middle and late stages of storage roots but not in primary fibrous roots, or secondary fibrous roots. The inverse expression pattern of sucrose transporters, cell wall acid invertase, and soluble acid invertase in these corresponding organs supported the presence of a symplastic sucrose unloading pathway. The transcription profile of genes involved in symplastic unloading and their significantly positive correlation with the starch yield at the population level confirmed that symplastic sucrose transport is vitally important in the development of cassava storage roots. CONCLUSIONS In this study, we revealed that the cassava storage root phloem sucrose unloading pattern was predominantly a symplastic unloading pattern. This pattern is essential for efficient starch accumulation in high-yielding varieties compared with low-yielding wild ancestors.
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Affiliation(s)
- Kun Pan
- Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agriculture Sciences, Haikou, 571101, China
- Hainan Medical University, Haikou, 571199, China
| | - Cheng Lu
- Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agriculture Sciences, Haikou, 571101, China
| | - Peixian Nie
- Shandong Institute of Pomology, Shandong Academy of Agricultural Sciences, Taian, 271000, Shandong, China
| | - Meizhen Hu
- Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agriculture Sciences, Haikou, 571101, China
| | - Xincheng Zhou
- Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agriculture Sciences, Haikou, 571101, China
| | - Xin Chen
- Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agriculture Sciences, Haikou, 571101, China
| | - Wenquan Wang
- Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agriculture Sciences, Haikou, 571101, China.
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15
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Blicharz S, Beemster GT, Ragni L, De Diego N, Spíchal L, Hernándiz AE, Marczak Ł, Olszak M, Perlikowski D, Kosmala A, Malinowski R. Phloem exudate metabolic content reflects the response to water-deficit stress in pea plants (Pisum sativum L.). Plant J 2021; 106:1338-1355. [PMID: 33738886 PMCID: PMC8360158 DOI: 10.1111/tpj.15240] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 03/09/2021] [Accepted: 03/15/2021] [Indexed: 05/31/2023]
Abstract
Drought stress impacts the quality and yield of Pisum sativum. Here, we show how short periods of limited water availability during the vegetative stage of pea alters phloem sap content and how these changes are connected to strategies used by plants to cope with water deficit. We have investigated the metabolic content of phloem sap exudates and explored how this reflects P. sativum physiological and developmental responses to drought. Our data show that drought is accompanied by phloem-mediated redirection of the components that are necessary for cellular respiration and the proper maintenance of carbon/nitrogen balance during stress. The metabolic content of phloem sap reveals a shift from anabolic to catabolic processes as well as the developmental plasticity of P. sativum plants subjected to drought. Our study underlines the importance of phloem-mediated transport for plant adaptation to unfavourable environmental conditions. We also show that phloem exudate analysis can be used as a useful proxy to study stress responses in plants. We propose that the decrease in oleic acid content within phloem sap could be considered as a potential marker of early signalling events mediating drought response.
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Affiliation(s)
- Sara Blicharz
- Integrative Plant Biology TeamInstitute of Plant Genetics Polish Academy of Sciencesul. Strzeszyńska 34Poznań60‐479Poland
| | - Gerrit T.S. Beemster
- Laboratory for Integrated Molecular Plant Physiology Research (IMPRES)Department of BiologyUniversity of AntwerpGroenenborgerlaan 171Antwerpen2020Belgium
| | - Laura Ragni
- ZMBP‐Center for Plant Molecular BiologyUniversity of TübingenTübingenGermany
| | - Nuria De Diego
- Department of Chemical Biology and GeneticsCentre of the Region Haná for Biotechnological and Agricultural ResearchFaculty of SciencePalacký UniversityOlomoucCzech Republic
| | - Lukas Spíchal
- Department of Chemical Biology and GeneticsCentre of the Region Haná for Biotechnological and Agricultural ResearchFaculty of SciencePalacký UniversityOlomoucCzech Republic
| | - Alba E. Hernándiz
- Department of Chemical Biology and GeneticsCentre of the Region Haná for Biotechnological and Agricultural ResearchFaculty of SciencePalacký UniversityOlomoucCzech Republic
| | - Łukasz Marczak
- Institute of Bioorganic Chemistry Polish Academy of SciencesNoskowskiego 12/14Poznan61‐704Poland
| | - Marcin Olszak
- Department of Plant BiochemistryInstitute of Biochemistry and Biophysics Polish Academy of Sciencesul. Pawińskiego 5aWarsaw02‐106Poland
| | - Dawid Perlikowski
- Plant Physiology TeamInstitute of Plant Genetics Polish Academy of Sciencesul. Strzeszyńska 34Poznań60‐479Poland
| | - Arkadiusz Kosmala
- Plant Physiology TeamInstitute of Plant Genetics Polish Academy of Sciencesul. Strzeszyńska 34Poznań60‐479Poland
| | - Robert Malinowski
- Integrative Plant Biology TeamInstitute of Plant Genetics Polish Academy of Sciencesul. Strzeszyńska 34Poznań60‐479Poland
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16
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Abstract
Neck shrivel is a quality disorder of European plum (Prunus × domestica L.). It has been suggested that backflow in the xylem (from fruit to tree) could contribute to the incidence of neck shrivel in plum. The objective was to quantify rates of xylem, phloem and of transpiration flow in developing plum fruit. Using linear variable displacement transducers, changes in fruit volume were recorded 1) in un-treated control fruit, 2) in fruit that had their pedicels steam-girdled (phloem interrupted, xylem still functional) and 3) in detached fruit, left in the canopy (xylem and phloem interrupted). Xylem flow rates were occasionally negative in the early hours after sunrise, indicating xylem sap backflow from fruit to tree. Later in the day, xylem flows were positive and generally higher in daytime and lower at night. Significant phloem flow occurred in daytime, but ceased after sunset. During stage II (but not during stage III), the rates of xylem flow and transpiration were variable and closely related to atmospheric vapor pressure deficit. The relative contribution of xylem inflow to total sap inflow averaged 79% during stage II, decreasing to 25% during stage III. In contrast, phloem sap inflow averaged 21% of total sap inflow during stage II, increasing to 75% in stage III. Our results indicate that xylem backflow occurs early in the day. However, xylem backflow rates are considered too low to significantly contribute to the incidence of neck shrivel.
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Affiliation(s)
- Andreas Winkler
- Institute for Horticultural Production Systems, Leibniz-University Hannover, Hannover, Germany
| | - Moritz Knoche
- Institute for Horticultural Production Systems, Leibniz-University Hannover, Hannover, Germany
- * E-mail:
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17
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van den Herik B, Bergonzi S, Bachem CWB, ten Tusscher K. Modelling the physiological relevance of sucrose export repression by an Flowering Time homolog in the long-distance phloem of potato. Plant Cell Environ 2021; 44:792-806. [PMID: 33314152 PMCID: PMC7986384 DOI: 10.1111/pce.13977] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 12/03/2020] [Accepted: 12/03/2020] [Indexed: 05/31/2023]
Abstract
Yield of harvestable plant organs depends on photosynthetic assimilate production in source leaves, long-distance sucrose transport and sink-strength. While photosynthesis optimization has received considerable interest for optimizing plant yield, the potential for improving long-distance sucrose transport has received far less attention. Interestingly, a recent potato study demonstrates that the tuberigen StSP6A binds to and reduces activity of the StSWEET11 sucrose exporter. While the study suggested that reducing phloem sucrose efflux may enhance tuber yield, the precise mechanism and physiological relevance of this effect remained an open question. Here, we develop the first mechanistic model for sucrose transport, parameterized for potato plants. The model incorporates SWEET-mediated sucrose export, SUT-mediated sucrose retrieval from the apoplast and StSP6A-StSWEET11 interactions. Using this model, we were able to substantiate the physiological relevance of the StSP6A-StSWEET11 interaction in the long-distance phloem for potato tuber yield, as well as to show the non-linear nature of this effect.
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Affiliation(s)
- Bas van den Herik
- Computational Developmental BiologyUtrecht UniversityUtrechtThe Netherlands
| | - Sara Bergonzi
- Plant BreedingWageningen University & ResearchWageningenThe Netherlands
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18
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Anjali A, Fatima U, Senthil-Kumar M. The ins and outs of SWEETs in plants: Current understanding of the basics and their prospects in crop improvement. J Biosci 2021; 46:100. [PMID: 34785627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Sugar will eventually be exported transporters (SWEETs), a newly discovered class of sugar transporters, play a significant role in sugar efflux processes across various kingdoms of life. In fact, SWEETs have a long evolutionary path from prokaryotes to higher plants. In plants, they are involved in developmental processes, including nectar secretion, pollen nutrition, and seed filling. While the role of SWEETs has been well studied in biotic stresses, particularly their manipulation by pathogens for sugar acquisition, they have also been linked to many abiotic stresses. Although the phylogenetic relationships and solved structures of SWEETs in different plants have been revealed, their regulation remains unexplored. The current review deals with all the exciting discoveries around SWEETs, including their classification and diversity, and bridges the gaps in their evolutionary story, from bacterial semiSWEETs to eukaryotic SWEETs. We also critically examine SWEETs at genomic, transcriptomic, and proteomic levels, as evinced by recently published examples from grain, millet, and horticultural crops. In addition, we highlight the possibilities of utilizing SWEETs in applications such as bioethanol production and disease diagnostic markers. We attempt to elucidate and unify findings related to the yet unsolved puzzle of SWEET regulation in plants to improve crop production and protection for sustainable agriculture.
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Affiliation(s)
- Anjali Anjali
- National Institute of Plant Genome Research, Aruna Asaf Alig Marg, New Delhi 110 067, India
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19
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Fang S, Shang X, Yao Y, Li W, Guo W. NST- and SND-subgroup NAC proteins coordinately act to regulate secondary cell wall formation in cotton. Plant Sci 2020; 301:110657. [PMID: 33218627 DOI: 10.1016/j.plantsci.2020.110657] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 08/24/2020] [Accepted: 08/29/2020] [Indexed: 06/11/2023]
Abstract
Secondary cell wall (SCW) has a strong impact on plant growth and adaptation to the environments. Previous studies have shown that NAC (NAM, ATAF1/2, and CUC2) transcription factors act as key regulators of SCW biosynthesis. However, the regulatory network triggered by NAC proteins is largely unknown, especially in cotton, a model plant for SCW development studies. Here, we show that several cotton NAC transcription factors are clustered in the same group with Arabidopsis secondary wall NACs (SWNs), including secondary wall-associated NAC domain protein1 (SND1) and NAC secondary wall thickening promoting factor1/2 (NST1/2), so we name these cotton orthologs as SND1s and NST1s. We found that simultaneous silencing of SND1s and NST1s led to severe xylem and phloem developmental defect in cotton stems, however silencing either SND1s or NST1s alone had no visible phenotype. Silencing both SND1s and NST1s but not one subgroup caused decreased expression of a set of SCW-associated genes, while over-expression of cotton SWNs in tobacco leaves resulted in SCW deposition. SWNs could bind the promoter of MYB46 and MYB83, which are highly expressed in SCW-rich tissues of cotton. In total, our data provide evidence that cotton SWNs positively and coordinately regulate SCW formation.
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Affiliation(s)
- Shuai Fang
- State Key Laboratory of Crop Genetics & Germplasm Enhancement, Hybrid Cotton R & D Engineering Research Center, Ministry of Education, Nanjing Agricultural University, Nanjing, 210095, China
| | - Xiaoguang Shang
- State Key Laboratory of Crop Genetics & Germplasm Enhancement, Hybrid Cotton R & D Engineering Research Center, Ministry of Education, Nanjing Agricultural University, Nanjing, 210095, China
| | - Yue Yao
- State Key Laboratory of Crop Genetics & Germplasm Enhancement, Hybrid Cotton R & D Engineering Research Center, Ministry of Education, Nanjing Agricultural University, Nanjing, 210095, China
| | - Weixi Li
- State Key Laboratory of Crop Genetics & Germplasm Enhancement, Hybrid Cotton R & D Engineering Research Center, Ministry of Education, Nanjing Agricultural University, Nanjing, 210095, China
| | - Wangzhen Guo
- State Key Laboratory of Crop Genetics & Germplasm Enhancement, Hybrid Cotton R & D Engineering Research Center, Ministry of Education, Nanjing Agricultural University, Nanjing, 210095, China.
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20
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Zhang Y, Xu L, Chen S, Qiang S. Transcription-mediated tissue-specific lignification of vascular bundle causes trade-offs between growth and defence capacity during invasion of Solidago canadensis. Plant Sci 2020; 301:110638. [PMID: 33218618 DOI: 10.1016/j.plantsci.2020.110638] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 07/06/2020] [Accepted: 08/12/2020] [Indexed: 06/11/2023]
Abstract
Allocation of more resources to growth but less to defense causing growth vigor of invasive alien plant populations contributes to successful invasion. However, few studies has addressed to relationship between vascular development variation and this mechanism. In this study, a common garden experimentwas established to compare the growth and vascular bundle development between native and introduced populations of Solidago canadensis, which is a wide-distributed invasive species in China. Our results suggested that the rapid growth of introduced populations could be explained by the well-developed and highly lignified xylem; while native populations present more developed and highly lignified phloem, which contributed more resistance to the infection of Sclerotiun rofsii compared with introduced populations. This difference was resulted from tissue-specific tradeoff distribution of lignification related gene expression between xylem and phloem, which is regulated by upstream MYB transcription factors. Our study gives a novel insight of mechanism that explain invasion success: lignin-related gene transcription-mediated tissue-specific lignification of vascular bundle contributes tradeoffs in resource allocation between growth and defence capacity during successful invasion of S. canadensis.
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Affiliation(s)
- Yu Zhang
- Weed Research Laboratory, Nanjing Agricultural University, Nanjing, 210095, China
| | - Lingjun Xu
- Weed Research Laboratory, Nanjing Agricultural University, Nanjing, 210095, China
| | - Shiguo Chen
- Weed Research Laboratory, Nanjing Agricultural University, Nanjing, 210095, China
| | - Sheng Qiang
- Weed Research Laboratory, Nanjing Agricultural University, Nanjing, 210095, China.
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21
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Vernay A, Tian X, Chi J, Linder S, Mäkelä A, Oren R, Peichl M, Stangl ZR, Tor-Ngern P, Marshall JD. Estimating canopy gross primary production by combining phloem stable isotopes with canopy and mesophyll conductances. Plant Cell Environ 2020; 43:2124-2142. [PMID: 32596814 DOI: 10.1111/pce.13835] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 06/21/2020] [Accepted: 06/22/2020] [Indexed: 06/11/2023]
Abstract
Gross primary production (GPP) is a key component of the forest carbon cycle. However, our knowledge of GPP at the stand scale remains uncertain, because estimates derived from eddy covariance (EC) rely on semi-empirical modelling and the assumptions of the EC technique are sometimes not fully met. We propose using the sap flux/isotope method as an alternative way to estimate canopy GPP, termed GPPiso/SF , at the stand scale and at daily resolution. It is based on canopy conductance inferred from sap flux and intrinsic water-use efficiency estimated from the stable carbon isotope composition of phloem contents. The GPPiso/SF estimate was further corrected for seasonal variations in photosynthetic capacity and mesophyll conductance. We compared our estimate of GPPiso/SF to the GPP derived from PRELES, a model parameterized with EC data. The comparisons were performed in a highly instrumented, boreal Scots pine forest in northern Sweden, including a nitrogen fertilized and a reference plot. The resulting annual and daily GPPiso/SF estimates agreed well with PRELES, in the fertilized plot and the reference plot. We discuss the GPPiso/SF method as an alternative which can be widely applied without terrain restrictions, where the assumptions of EC are not met.
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Affiliation(s)
- Antoine Vernay
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden
| | - Xianglin Tian
- Department of Forest Sciences, University of Helsinki, Helsinki, Finland
| | - Jinshu Chi
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden
| | - Sune Linder
- Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences, Alnarp, Sweden
| | - Annikki Mäkelä
- Department of Forest Sciences, University of Helsinki, Helsinki, Finland
| | - Ram Oren
- Department of Forest Sciences, University of Helsinki, Helsinki, Finland
- Division of Environmental Science & Policy, Nicholas School of the Environment, Duke University, Durham, North Carolina, USA
- Department of Civil & Environmental Engineering, Pratt School of Engineering, Duke University, Durham, North Carolina, USA
| | - Matthias Peichl
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden
| | - Zsofia R Stangl
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden
| | - Pantana Tor-Ngern
- Department of Environmental Science, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
- Environment, Health and Social Data Analytics Research Group, Chulalongkorn University, Bangkok, Thailand
| | - John D Marshall
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden
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22
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Horgan FG, Jauregui A, Peñalver Cruz A, Crisol Martínez E, Bernal CC. Changes in reflectance of rice seedlings during planthopper feeding as detected by digital camera: Potential applications for high-throughput phenotyping. PLoS One 2020; 15:e0238173. [PMID: 32853293 PMCID: PMC7451558 DOI: 10.1371/journal.pone.0238173] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 08/11/2020] [Indexed: 11/19/2022] Open
Abstract
Damage to grasses and cereals by phloem-feeding herbivores is manifest as nutrient and chlorophyll loss, desiccation, and a gradual decline in host vigour. Chlorophyll loss in particular leads to a succession of colour changes before eventual host death. Depending on the attacking herbivore species, colour changes can be difficult to detect with the human eye. This study used digital images to examine colour changes of rice seedlings during feeding by the brown planthopper, Nilaparvata lugens (Stål) and whitebacked planthopper, Sogatella furcifera (Horváth). Values for red (580 nm), green (540 nm) and blue (550 nm) reflectance for 39 rice varieties during seedling seed-box tests were derived from images captured with a digital camera. Red and blue reflectance gradually increased as herbivore damage progressed until final plant death. Red reflectance was greater from plants attacked by the brown planthopper than plants attacked by the whitebacked planthopper, which had proportionately more green and blue reflectance, indicating distinct impacts by the two planthoppers on their hosts. Analysis of digital images was used to discriminate variety responses to the two planthoppers. Ordination methods based on red-green-blue reflectance and vegetation indices such as the Green Leaf Index (GLI) that included blue reflectance were more successful than two-colour indices or indices based on hue, saturation and brightness in discriminating between damage responses among varieties. We make recommendations to advance seed-box screening methods for cereal resistance to phloem feeders and demonstrate how images from digital cameras can be used to improve the quality of data captured during high-throughput phenotyping.
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Affiliation(s)
- Finbarr G. Horgan
- EcoLaVerna Integral Restoration Ecology, Bridestown, Kildinan, Co. Cork, Ireland
- Environment and Sustainable Resource Management, University College Dublin, Belfield, Dublin, Ireland
| | - Artzai Jauregui
- Unidad de Diseño, Departamento de Branding, Dirección de Comunicaciones Corporativas, Universidad de Talca, Talca, Chile
- International Rice Research Institute, Metro Manila, Philippines
| | - Ainara Peñalver Cruz
- International Rice Research Institute, Metro Manila, Philippines
- Laboratorio de Control Biológico, Instituto de Ciencias Biológicas, Universidad de Talca, Talca, Chile
| | - Eduardo Crisol Martínez
- EcoLaVerna Integral Restoration Ecology, Bridestown, Kildinan, Co. Cork, Ireland
- Department of Agroecology, COEXPHAL (Association of Vegetable and Fruit Growers of Almeria), La Mojonera, Almeria, Spain
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23
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Knoblauch J, Knoblauch M, Vasina VV, Peters WS. Sieve elements rapidly develop 'nacreous walls' following injury - a common wounding response? Plant J 2020; 102:797-808. [PMID: 31883138 DOI: 10.1111/tpj.14665] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 11/19/2019] [Accepted: 12/09/2019] [Indexed: 06/10/2023]
Abstract
Thick glistening cell walls occur in sieve tubes of all major land plant taxa. Historically, these 'nacreous walls' have been considered a diagnostic feature of sieve elements; they represent a conundrum, though, in the context of the widely accepted pressure-flow theory as they severely constrict sieve tubes. We employed the cucurbit Gerrardanthus macrorhizus as a model to study nacreous walls in sieve elements by standard and in situ confocal microscopy and electron microscopy, focusing on changes in functional sieve tubes that occur when prepared for microscopic observation. Over 90% of sieve elements in tissue sections processed for microscopy by standard methods exhibit nacreous walls. Sieve elements in whole, live plants that were actively transporting as shown by phloem-mobile tracers, lacked nacreous walls and exhibited open lumina of circular cross-sections instead, an appropriate structure for Münch-type mass flow of the cell contents. Puncturing of transporting sieve elements with micropipettes triggered the rapid (<1 min) development of nacreous walls that occluded the cell lumen almost completely. We conclude that nacreous walls are preparation artefacts rather than structural features of transporting sieve elements. Nacreous walls in land plants resemble the reversibly swellable walls found in various algae, suggesting that they may function in turgor buffering, the amelioration of osmotic stress, wounding-induced sieve tube occlusion, and possibly local defence responses of the phloem.
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Affiliation(s)
- Jan Knoblauch
- School of Biological Sciences, Washington State University, PO Box 644236, Pullman, WA, 99164, USA
| | - Michael Knoblauch
- School of Biological Sciences, Washington State University, PO Box 644236, Pullman, WA, 99164, USA
| | - Viktoriya V Vasina
- School of Biological Sciences, Washington State University, PO Box 644236, Pullman, WA, 99164, USA
| | - Winfried S Peters
- School of Biological Sciences, Washington State University, PO Box 644236, Pullman, WA, 99164, USA
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Kloth KJ, Kormelink R. Defenses against Virus and Vector: A Phloem-Biological Perspective on RTM- and SLI1-Mediated Resistance to Potyviruses and Aphids. Viruses 2020; 12:E129. [PMID: 31979012 PMCID: PMC7077274 DOI: 10.3390/v12020129] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 01/17/2020] [Accepted: 01/19/2020] [Indexed: 12/12/2022] Open
Abstract
Combining plant resistance against virus and vector presents an attractive approach to reduce virus transmission and virus proliferation in crops. RestrictedTobacco-etch virus Movement (RTM) genes confer resistance to potyviruses by limiting their long-distance transport. Recently, a close homologue of one of the RTM genes, SLI1, has been discovered but this gene instead confers resistance to Myzus persicae aphids, a vector of potyviruses. The functional connection between resistance to potyviruses and aphids, raises the question whether plants have a basic defense system in the phloem against biotic intruders. This paper provides an overview on restricted potyvirus phloem transport and restricted aphid phloem feeding and their possible interplay, followed by a discussion on various ways in which viruses and aphids gain access to the phloem sap. From a phloem-biological perspective, hypotheses are proposed on the underlying mechanisms of RTM- and SLI1-mediated resistance, and their possible efficacy to defend against systemic viruses and phloem-feeding vectors.
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Affiliation(s)
- Karen J. Kloth
- Laboratory of Entomology, Wageningen University and Research, 6700 AA Wageningen, The Netherlands
| | - Richard Kormelink
- Laboratory of Virology, Wageningen University and Research, 6700 AA Wageningen, The Netherlands;
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25
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Abstract
Complex distribution networks are pervasive in biology. Examples include nutrient transport in the slime mold Physarum polycephalum as well as mammalian and plant venation. Adaptive rules are believed to guide development of these networks and lead to a reticulate, hierarchically nested topology that is both efficient and resilient against perturbations. However, as of yet, no mechanism is known that can generate such networks on all scales. We show how hierarchically organized reticulation can be constructed and maintained through spatially correlated load fluctuations on a particular length scale. We demonstrate that the network topologies generated represent a trade-off between optimizing transport efficiency, construction cost, and damage robustness and identify the Pareto-efficient front that evolution is expected to favor and select for. We show that the typical fluctuation length scale controls the position of the networks on the Pareto front and thus on the spectrum of venation phenotypes.
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Affiliation(s)
- Henrik Ronellenfitsch
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Eleni Katifori
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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26
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Mehdi R, Lamm CE, Bodampalli Anjanappa R, Müdsam C, Saeed M, Klima J, Kraner ME, Ludewig F, Knoblauch M, Gruissem W, Sonnewald U, Zierer W. Symplasmic phloem unloading and radial post-phloem transport via vascular rays in tuberous roots of Manihot esculenta. J Exp Bot 2019; 70:5559-5573. [PMID: 31232453 PMCID: PMC6812707 DOI: 10.1093/jxb/erz297] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Accepted: 06/15/2019] [Indexed: 05/04/2023]
Abstract
Cassava (Manihot esculenta) is one of the most important staple food crops worldwide. Its starchy tuberous roots supply over 800 million people with carbohydrates. Yet, surprisingly little is known about the processes involved in filling of those vital storage organs. A better understanding of cassava carbohydrate allocation and starch storage is key to improving storage root yield. Here, we studied cassava morphology and phloem sap flow from source to sink using transgenic pAtSUC2::GFP plants, the phloem tracers esculin and 5(6)-carboxyfluorescein diacetate, as well as several staining techniques. We show that cassava performs apoplasmic phloem loading in source leaves and symplasmic unloading into phloem parenchyma cells of tuberous roots. We demonstrate that vascular rays play an important role in radial transport from the phloem to xylem parenchyma cells in tuberous roots. Furthermore, enzymatic and proteomic measurements of storage root tissues confirmed high abundance and activity of enzymes involved in the sucrose synthase-mediated pathway and indicated that starch is stored most efficiently in the outer xylem layers of tuberous roots. Our findings form the basis for biotechnological approaches aimed at improved phloem loading and enhanced carbohydrate allocation and storage in order to increase tuberous root yield of cassava.
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Affiliation(s)
- Rabih Mehdi
- Biochemistry, Department of Biology, Friedrich-Alexander University Erlangen-Nuremberg, Erlangen, Germany
| | - Christian E Lamm
- Biochemistry, Department of Biology, Friedrich-Alexander University Erlangen-Nuremberg, Erlangen, Germany
| | | | - Christina Müdsam
- Biochemistry, Department of Biology, Friedrich-Alexander University Erlangen-Nuremberg, Erlangen, Germany
| | - Muhammad Saeed
- Biochemistry, Department of Biology, Friedrich-Alexander University Erlangen-Nuremberg, Erlangen, Germany
| | - Janine Klima
- Biochemistry, Department of Biology, Friedrich-Alexander University Erlangen-Nuremberg, Erlangen, Germany
| | - Max E Kraner
- Biochemistry, Department of Biology, Friedrich-Alexander University Erlangen-Nuremberg, Erlangen, Germany
| | - Frank Ludewig
- Biochemistry, Department of Biology, Friedrich-Alexander University Erlangen-Nuremberg, Erlangen, Germany
| | - Michael Knoblauch
- School of Biological Sciences, Washington State University, Pullman, WA, USA
| | - Wilhelm Gruissem
- Plant Biotechnology, Department of Biology, ETH Zurich, Zurich, Switzerland
- Advanced Plant Biotechnology Center, National Chung Hsing University, Taichung City, Taiwan
| | - Uwe Sonnewald
- Biochemistry, Department of Biology, Friedrich-Alexander University Erlangen-Nuremberg, Erlangen, Germany
| | - Wolfgang Zierer
- Biochemistry, Department of Biology, Friedrich-Alexander University Erlangen-Nuremberg, Erlangen, Germany
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27
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Perri S, Katul GG, Molini A. Xylem-phloem hydraulic coupling explains multiple osmoregulatory responses to salt stress. New Phytol 2019; 224:644-662. [PMID: 31349369 DOI: 10.1111/nph.16072] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 07/11/2019] [Indexed: 06/10/2023]
Abstract
Salinity is known to affect plant productivity by limiting leaf-level carbon exchange, root water uptake, and carbohydrates transport in the phloem. However, the mechanisms through which plants respond to salt exposure by adjusting leaf gas exchange and xylem-phloem flow are still mostly unexplored. A physically based model coupling xylem, leaf, and phloem flows is here developed to explain different osmoregulation patterns across species. Hydraulic coupling is controlled by leaf water potential, ψl , and determined under four different maximization hypotheses: water uptake (1), carbon assimilation (2), sucrose transport (3), or (4) profit function - i.e. carbon gain minus hydraulic risk. All four hypotheses assume that finite transpiration occurs, providing a further constraint on ψl . With increasing salinity, the model captures different transpiration patterns observed in halophytes (nonmonotonic) and glycophytes (monotonically decreasing) by reproducing the species-specific strength of xylem-leaf-phloem coupling. Salt tolerance thus emerges as plant's capability of differentiating between salt- and drought-induced hydraulic risk, and to regulate internal flows and osmolytes accordingly. Results are shown to be consistent across optimization schemes (1-3) for both halophytes and glycophytes. In halophytes, however, profit-maximization (4) predicts systematically higher ψl than (1-3), pointing to the need of an updated definition of hydraulic cost for halophytes under saline conditions.
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Affiliation(s)
- Saverio Perri
- Masdar Institute, Khalifa University of Science and Technology, PO Box 54224, Abu Dhabi, United Arab Emirates
- Department of Civil Infrastructure and Environmental Engineering, Khalifa University of Science and Technology, PO Box 127788, Abu Dhabi, United Arab Emirates
| | - Gabriel G Katul
- Nicholas School of the Environment, Duke University, Durham, NC, 27710, USA
- Department of Civil and Environmental Engineering, Duke University, Durham, NC, 27708, USA
| | - Annalisa Molini
- Masdar Institute, Khalifa University of Science and Technology, PO Box 54224, Abu Dhabi, United Arab Emirates
- Department of Civil Infrastructure and Environmental Engineering, Khalifa University of Science and Technology, PO Box 127788, Abu Dhabi, United Arab Emirates
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28
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Chen JJ, Wang LY, Immanen J, Nieminen K, Spicer R, Helariutta Y, Zhang J, He XQ. Differential regulation of auxin and cytokinin during the secondary vascular tissue regeneration in Populus trees. New Phytol 2019; 224:188-201. [PMID: 31230359 DOI: 10.1111/nph.16019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 06/14/2019] [Indexed: 05/04/2023]
Abstract
Tissue regeneration upon wounding in plants highlights the developmental plasticity of plants. Previous studies have described the morphological and molecular changes of secondary vascular tissue (SVT) regeneration after large-scale bark girdling in trees. However, how phytohormones regulate SVT regeneration is still unknown. Here, we established a novel in vitro SVT regeneration system in the hybrid aspen (Populus tremula × Populus tremuloides) clone T89 to bypass the limitation of using field-grown trees. The effects of phytohormones on SVT regeneration were investigated by applying exogenous hormones and utilizing various transgenic trees. Vascular tissue-specific markers and hormonal response factors were also examined during SVT regeneration. Using this in vitro regeneration system, we demonstrated that auxin and cytokinin differentially regulate phloem and cambium regeneration. Whereas auxin is sufficient to induce regeneration of phloem prior to continuous cambium restoration, cytokinin only promotes the formation of new phloem, not cambium. The positive role of cytokinin on phloem regeneration was further confirmed in cytokinin overexpression trees. Analysis of a DR5 reporter transgenic line further suggested that cytokinin blocks the re-establishment of auxin gradients, which is required for the cambium formation. Investigation on the auxin and cytokinin signalling genes indicated these two hormones interact to regulate SVT regeneration. Taken together, the in vitro SVT regeneration system allows us to make use of various molecular and genetic tools to investigate SVT regeneration. Our results confirmed that complementary auxin and cytokinin domains are required for phloem and cambium reconstruction.
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Affiliation(s)
- Jia-Jia Chen
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, 100871, China
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki, 00014, Finland
- Organismal and Evolutionary Biology Research Programme, Faculty of Biological and Environmental Sciences, Viikki Plant Science Centre, University of Helsinki, Helsinki, 00014, Finland
| | - Ling-Yan Wang
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, 100871, China
| | - Juha Immanen
- Organismal and Evolutionary Biology Research Programme, Faculty of Biological and Environmental Sciences, Viikki Plant Science Centre, University of Helsinki, Helsinki, 00014, Finland
- Natural Resources Institute Finland (Luke), Production Systems, Plant Genetics, Helsinki, 00790, Finland
| | - Kaisa Nieminen
- Natural Resources Institute Finland (Luke), Production Systems, Plant Genetics, Helsinki, 00790, Finland
| | - Rachel Spicer
- Department of Botany, Connecticut College, New London, CT, 06320, USA
| | - Ykä Helariutta
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki, 00014, Finland
- Organismal and Evolutionary Biology Research Programme, Faculty of Biological and Environmental Sciences, Viikki Plant Science Centre, University of Helsinki, Helsinki, 00014, Finland
- The Sainsbury Laboratory, University of Cambridge, Bateman Street, Cambridge, CB2 1LR, UK
| | - Jing Zhang
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki, 00014, Finland
- Organismal and Evolutionary Biology Research Programme, Faculty of Biological and Environmental Sciences, Viikki Plant Science Centre, University of Helsinki, Helsinki, 00014, Finland
| | - Xin-Qiang He
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, 100871, China
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29
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Lezzhov AA, Atabekova AK, Tolstyko EA, Lazareva EA, Solovyev AG. RNA phloem transport mediated by pre-miRNA and viral tRNA-like structures. Plant Sci 2019; 284:99-107. [PMID: 31084885 DOI: 10.1016/j.plantsci.2019.04.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 04/03/2019] [Accepted: 04/05/2019] [Indexed: 06/09/2023]
Abstract
Phloem-mobile mRNAs are assumed to contain sequence elements directing RNA to the phloem translocation pathway. One of such elements is represented by tRNA sequences embedded in untranslated regions of many mRNAs, including those proved to be mobile. Genomic RNAs of a number of plant viruses possess a 3'-terminal tRNA-like structures (TLSs) only distantly related to genuine tRNAs, but nevertheless aminoacylated and capable of interaction with some tRNA-binding proteins. Here, we elaborated an experimental system for analysis of RNA phloem transport based on an engineered RNA of Potato virus X capable of replication, but not encapsidation and movement in plants. The TLSs of Brome mosaic virus, Tobacco mosaic virus and Turnip yellow mosaic virus were demonstrated to enable the phloem transport of foreign RNA. A miRNA precursor, pre-miR390b, was also found to render RNA competent for the phloem transport. In line with this, sequences of miRNA precursors were identified in a Cucurbita maxima phloem transcriptome, supporting the hypothesis that, at least in some cases, miRNA phloem signaling can involve miRNA precursors. Collectively, the data presented here suggest that RNA molecules can be directed into the phloem translocation pathway by structured RNA elements such as those of viral TLSs and miRNA precursors.
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Affiliation(s)
- Alexander A Lezzhov
- Faculty of Bioengineering and Bioinformatics, Moscow State University, Moscow 119991, Russia
| | - Anastasia K Atabekova
- Department of Virology, Biological Faculty, Moscow State University, Moscow 119234, Russia
| | - Eugeny A Tolstyko
- Department of Virology, Biological Faculty, Moscow State University, Moscow 119234, Russia
| | - Ekaterina A Lazareva
- Department of Virology, Biological Faculty, Moscow State University, Moscow 119234, Russia
| | - Andrey G Solovyev
- Department of Virology, Biological Faculty, Moscow State University, Moscow 119234, Russia; Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119992, Russia; Sechenov First Moscow State Medical University, Institute of Molecular Medicine, Moscow 119991, Russia.
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30
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Corelli Grappadelli L, Morandi B, Manfrini L, O'Connell M. Apoplasmic and simplasmic phloem unloading mechanisms: Do they co-exist in Angeleno plums under demanding environmental conditions? J Plant Physiol 2019; 237:104-110. [PMID: 31055228 DOI: 10.1016/j.jplph.2019.04.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Revised: 04/05/2019] [Accepted: 04/08/2019] [Indexed: 05/13/2023]
Abstract
Biophysical fruit growth depends on a balance among the vascular and transpiration flows entering/exiting the fruit via phloem, xylem and through the epidermis. There is no information on vascular flows of Japanese plums, a species characterized by high-sugar content of its fruit at harvest. Vascular flows of Angeleno plums were monitored by fruit gauges during late fruit development, under the dry environment of the Goulburn Valley, Victoria, Australia. Phloem, xylem flows and skin transpiratory losses were determined, as well as diurnal leaf, stem and fruit pressure potentials. Fruit seasonal development, skin conductance and dry matter accumulation were also monitored. Fruit grew following a double-sigmoid pattern, but fruit size increased only 3.1 g over the last 3 weeks of development. Fruit grew very little in the morning, primarily due to phloem inflows (0.05 g fruit-1hr-1), while water left the fruit via the xylem. Negligible skin transpiration was recorded for vapour pressure deficit (VPD) values below 3 kPa. This growth pattern, in the absence of skin transpiration, suggests apoplastic phloem unloading. However, at VPD values over 3 kPa (e.g. from early afternoon to a peak around 18:00 h), transpiratory losses through the skin (up to 0.25 g fruit-1hr-1) caused fruit to shrink, leading to enhanced phloem and xylem inflows (ca. 0.15 g fruit-1hr-1), a scenario that would correspond to symplastic phloem unloading. Over 24 h the fruit showed a slightly negative total growth, consistent with fruit growth measured in situ during the season at weekly intervals. A few fruit species are known to alter their phloem unloading mechanism, switching from symplastic to apoplastic during the season. Our data support the coexistence in Japanese plum of different phloem unloading strategies within the same day.
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Affiliation(s)
| | - Brunella Morandi
- Dept. of Agricultural and Food Sciences, University of Bologna, V.le Fanin 46, 40127, Bologna, Italy.
| | - Luigi Manfrini
- Dept. of Agricultural and Food Sciences, University of Bologna, V.le Fanin 46, 40127, Bologna, Italy.
| | - Mark O'Connell
- Department of Jobs, Precincts and Regions, 255 Ferguson Rd, Tatura, Victoria, 3616, Australia. Mark.O'
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31
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Takata N, Awano T, Nakata MT, Sano Y, Sakamoto S, Mitsuda N, Taniguchi T. Populus NST/SND orthologs are key regulators of secondary cell wall formation in wood fibers, phloem fibers and xylem ray parenchyma cells. Tree Physiol 2019; 39:514-525. [PMID: 30806711 DOI: 10.1093/treephys/tpz004] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 12/25/2018] [Accepted: 01/09/2019] [Indexed: 05/06/2023]
Abstract
Wood fibers form thick secondary cell wall (SCW) in xylem tissues to give mechanical support to trees. NAC SECONDARY WALL THICKENING PROMOTING FACTOR3/SECONDARY WALL-ASSOCIATED NAC DOMAIN PROTEIN 1 (NST3/SND1) and NST1 were identified as master regulators of SCW formation in xylem fiber cells in the model plant Arabidopsis thaliana. In Populus species, four NST/SND orthologs have been conserved and coordinately control SCW formation in wood fibers and phloem fibers. However, it remains to be elucidated whether SCW formation in other xylem cells, such as ray parenchyma cells and vessel elements, is regulated by NST/SND orthologs in poplar. We knocked out all NST/SND genes in hybrid aspen using the clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 9 nuclease (Cas9) system and investigated the detailed histological appearance of stem tissues in the knockout mutants. Observation by light microscopy and transmission electron microscopy showed that SCW was severely suppressed in wood fibers, phloem fibers and xylem ray parenchyma cells in the knockout mutants. Although almost all wood fibers lacked SCW, some fiber cells formed thick cell walls. The irregularly cell wall-forming fibers retained primary wall and SCW, and were mainly located in the vicinity of vessel elements. Field emission-scanning electron microscope observation showed that there were no apparent differences in the structural features of pits such as the shape and size between irregularly SCW-forming wood fibers in the knockout mutants and normal wood fibers in wild-type. Cell wall components such as cellulose, hemicellulose and lignin were deposited in the cell wall of irregularly SCW-forming wood fibers in quadruple mutants. Our results indicate that four NST/SND orthologs are master switches for SCW formation in wood fibers, xylem ray parenchyma cells and phloem fibers in poplar, while SCW is still formed in limited wood fibers, which are located at the region adjacent to vessel elements in the knockout mutants.
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Affiliation(s)
- Naoki Takata
- Forest Bio-Research Center, Forestry and Forest Products Research Institute, Hitachi, Ibaraki, Japan
| | - Tatsuya Awano
- Division of Forest and Biomaterials Science, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Miyuki T Nakata
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan
| | - Yuzou Sano
- Research Faculty of Agriculture, Hokkaido University, Sapporo, Japan
| | - Shingo Sakamoto
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan
| | - Nobutaka Mitsuda
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan
| | - Toru Taniguchi
- Forest Bio-Research Center, Forestry and Forest Products Research Institute, Hitachi, Ibaraki, Japan
- Forest Tree Breeding Center, Forestry and Forest Products Research Institute, Hitachi, Ibaraki, Japan
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Varsani S, Grover S, Zhou S, Koch KG, Huang PC, Kolomiets MV, Williams WP, Heng-Moss T, Sarath G, Luthe DS, Jander G, Louis J. 12-Oxo-Phytodienoic Acid Acts as a Regulator of Maize Defense against Corn Leaf Aphid. Plant Physiol 2019; 179:1402-1415. [PMID: 30643012 PMCID: PMC6446797 DOI: 10.1104/pp.18.01472] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Accepted: 01/03/2019] [Indexed: 05/25/2023]
Abstract
The corn leaf aphid (CLA; Rhopalosiphum maidis) is a phloem sap-sucking insect that attacks many cereal crops, including maize (Zea mays). We previously showed that the maize inbred line Mp708, which was developed by classical plant breeding, provides enhanced resistance to CLA. Here, using electrophysiological monitoring of aphid feeding behavior, we demonstrate that Mp708 provides phloem-mediated resistance to CLA. Furthermore, feeding by CLA on Mp708 plants enhanced callose deposition, a potential defense mechanism utilized by plants to limit aphid feeding and subsequent colonization. In maize, benzoxazinoids (BX) or BX-derived metabolites contribute to enhanced callose deposition by providing heightened resistance to CLA. However, BX and BX-derived metabolites were not significantly altered in CLA-infested Mp708 plants, indicating BX-independent defense against CLA. Evidence presented here suggests that the constitutively higher levels of 12-oxo-phytodienoic acid (OPDA) in Mp708 plants contributed to enhanced callose accumulation and heightened CLA resistance. OPDA enhanced the expression of ethylene biosynthesis and receptor genes, and the synergistic interactions of OPDA and CLA feeding significantly induced the expression of the transcripts encoding Maize insect resistance1-Cysteine Protease, a key defensive protein against insect pests, in Mp708 plants. Furthermore, exogenous application of OPDA on maize jasmonic acid-deficient plants caused enhanced callose accumulation and heightened resistance to CLA, suggesting that the OPDA-mediated resistance to CLA is independent of the jasmonic acid pathway. We further demonstrate that the signaling function of OPDA, rather than a direct toxic effect, contributes to enhanced CLA resistance in Mp708.
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Affiliation(s)
- Suresh Varsani
- Department of Entomology, University of Nebraska, Lincoln, Nebraska 68583
| | - Sajjan Grover
- Department of Entomology, University of Nebraska, Lincoln, Nebraska 68583
| | - Shaoqun Zhou
- Boyce Thompson Institute, Cornell University, Ithaca, New York 14853
- School of Integrated Plant Sciences, Cornell University, Ithaca, New York 14853
| | - Kyle G Koch
- Department of Entomology, University of Nebraska, Lincoln, Nebraska 68583
| | - Pei-Cheng Huang
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, Texas 77843
| | - Michael V Kolomiets
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, Texas 77843
| | - W Paul Williams
- United States Department of Agriculture-Agricultural Research Service, Corn Host Plant Resistance Research Unit, Mississippi State, Mississippi 39762
| | - Tiffany Heng-Moss
- Department of Entomology, University of Nebraska, Lincoln, Nebraska 68583
| | - Gautam Sarath
- Wheat, Sorghum, and Forage Research Unit, United States Department of Agriculture-Agricultural Research Service, Lincoln, Nebraska 68583
| | - Dawn S Luthe
- Department of Plant Science, Pennsylvania State University, University Park, Pennsylvania 16802
| | - Georg Jander
- Boyce Thompson Institute, Cornell University, Ithaca, New York 14853
| | - Joe Louis
- Department of Entomology, University of Nebraska, Lincoln, Nebraska 68583
- Department of Biochemistry, University of Nebraska, Lincoln, Nebraska 68583
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33
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Stanfield RC, Schulte PJ, Randolph KE, Hacke UG. Computational models evaluating the impact of sieve plates and radial water exchange on phloem pressure gradients. Plant Cell Environ 2019; 42:466-479. [PMID: 30074610 DOI: 10.1111/pce.13414] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Accepted: 07/20/2018] [Indexed: 05/06/2023]
Abstract
The sugar conducting phloem in angiosperms is a high resistance pathway made up of sieve elements bounded by sieve plates. The high resistance generated by sieve plates may be a trade-off for promoting quick sealing in the event of injury. However, previous modeling efforts have demonstrated a wide variation in the contribution of sieve plates towards total sieve tube resistance. In the current study, we generated high resolution scanning electron microscope images of sieve plates from balsam poplar and integrated them into a mathematical model using Comsol Multiphysics software. We found that sieve plates contribute upwards of 85% towards total sieve tube resistance. Utilizing the Navier-Stokes equations, we found that oblong pores may create over 50% more resistance in comparison with round pores of the same area. Although radial water flows in phloem sieve tubes have been previously considered, their impact on alleviating pressure gradients has not been fully studied. Our novel simulations find that radial water flow can reduce pressure requirements by half in comparison with modeled sieve tubes with no radial permeability. We discuss the implication that sieve tubes may alleviate pressure requirements to overcome high resistances by regulating their membrane permeability along the entire transport pathway.
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Affiliation(s)
- Ryan C Stanfield
- Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada
| | - Paul J Schulte
- School of Life Sciences, University of Nevada-Las Vegas, Las Vegas, Nevada
| | - Katie E Randolph
- School of Life Sciences, University of Nevada-Las Vegas, Las Vegas, Nevada
| | - Uwe G Hacke
- Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada
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34
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Salmon Y, Dietrich L, Sevanto S, Hölttä T, Dannoura M, Epron D. Drought impacts on tree phloem: from cell-level responses to ecological significance. Tree Physiol 2019; 39:173-191. [PMID: 30726983 DOI: 10.1093/treephys/tpy153] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 12/03/2018] [Accepted: 01/25/2019] [Indexed: 06/09/2023]
Abstract
On-going climate change is increasing the risk of drought stress across large areas worldwide. Such drought events decrease ecosystem productivity and have been increasingly linked to tree mortality. Understanding how trees respond to water shortage is key to predicting the future of ecosystem functions. Phloem is at the core of the tree functions, moving resources such as non-structural carbohydrates, nutrients, and defence and information molecules across the whole plant. Phloem function and ability to transport resources is tightly controlled by the balance of carbon and water fluxes within the tree. As such, drought is expected to impact phloem function by decreasing the amount of available water and new photoassimilates. Yet, the effect of drought on the phloem has received surprisingly little attention in the last decades. Here we review existing knowledge on drought impacts on phloem transport from loading and unloading processes at cellular level to possible effects on long-distance transport and consequences to ecosystems via ecophysiological feedbacks. We also point to new research frontiers that need to be explored to improve our understanding of phloem function under drought. In particular, we show how phloem transport is affected differently by increasing drought intensity, from no response to a slowdown, and explore how severe drought might actually disrupt the phloem transport enough to threaten tree survival. Because transport of resources affects other organisms interacting with the tree, we also review the ecological consequences of phloem response to drought and especially predatory, mutualistic and competitive relations. Finally, as phloem is the main path for carbon from sources to sink, we show how drought can affect biogeochemical cycles through changes in phloem transport. Overall, existing knowledge is consistent with the hypotheses that phloem response to drought matters for understanding tree and ecosystem function. However, future research on a large range of species and ecosystems is urgently needed to gain a comprehensive understanding of the question.
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Affiliation(s)
- Yann Salmon
- Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, Gustaf Hällströmin katu 2b, University of Helsinki, Helsinki, Finland
- Institute for Atmospheric and Earth System Research/Forest Sciences, Faculty of Agriculture and Forestry, Latokartanonkaari 7, University of Helsinki, Helsinki, Finland
| | - Lars Dietrich
- Department of Environmental Sciences, University of Basel, Schönbeinstrasse 6, Basel, Switzerland
| | - Sanna Sevanto
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, PO Box 1663 MA 495, Los Alamos, NM, USA
| | - Teemu Hölttä
- Institute for Atmospheric and Earth System Research/Forest Sciences, Faculty of Agriculture and Forestry, Latokartanonkaari 7, University of Helsinki, Helsinki, Finland
| | - Masako Dannoura
- Kyoto University, Laboratory of Ecosystem Production and Dynamics, Graduate School of Global Environmental Studies, Kyoto, Japan
- Kyoto University, Laboratory of Forest Utilization, Graduate School of Agriculture, Kyoto, Japan
| | - Daniel Epron
- Université de Lorraine, AgroParisTech, INRA, UMR Silva, Faculté des Sciences et Technologies, Nancy, France
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35
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Epron D, Dannoura M, Hölttä T. Introduction to the invited issue on phloem function and dysfunction. Tree Physiol 2019; 39:167-172. [PMID: 30785633 DOI: 10.1093/treephys/tpz007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 01/08/2019] [Accepted: 01/15/2019] [Indexed: 06/09/2023]
Affiliation(s)
- Daniel Epron
- Université de Lorraine, AgroParisTech, INRA, UMR Silva, Faculté des Sciences et Technologies, Nancy, France
| | - Masako Dannoura
- Kyoto University, Laboratory of Ecosystem Production and Dynamics, Graduate School of Global Environmental Studies, Kyoto, Japan
- Kyoto University, Laboratory of Forest Utilization, Graduate School of Agriculture, Kyoto, Japan
| | - Teemu Hölttä
- Institute for Atmospheric and Earth System Research/Forest Sciences, Faculty of Agriculture and Forestry, Latokartanonkaari 7, University of Helsinki, Helsinki, Finland
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Losada JM, Holbrook NM. Scaling of phloem hydraulic resistance in stems and leaves of the understory angiosperm shrub Illicium parviflorum. Am J Bot 2019; 106:244-259. [PMID: 30793276 DOI: 10.1002/ajb2.1241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 12/05/2018] [Indexed: 06/09/2023]
Abstract
PREMISE OF THE STUDY Recent studies in canopy-dominant trees revealed axial scaling of phloem structure. However, whether this pattern is found in woody plants of the understory, the environment of most angiosperms from the ANA grade (Amborellales-Nymphaeales-Austrobaileyales), is unknown. METHODS We used seedlings and adult plants of the understory tropical shrub Illicium parviflorum, a member of the lineage Austrobaileyales, to explore the anatomy and physiology of the phloem in their aerial parts, including changes through ontogeny. KEY RESULTS Adult plants maintain a similar proportion of phloem tissue across stem diameters, but larger conduit dimensions and number cause the hydraulic resistance of the phloem to decrease toward the base of the plant. Small sieve plate pores resulted in an overall higher sieve tube hydraulic resistance than has been reported in other woody angiosperms. Sieve elements increase in size from minor to major leaf veins, but were shorter and narrower in petioles. The low carbon assimilation rates of seedlings and mature plants contrasted with a 3-fold higher phloem sap velocity in seedlings, suggesting that phloem transport velocity is modulated through ontogeny. CONCLUSIONS The overall architecture of the phloem tissue in this understory angiosperm shrub scales in a manner consistent with taller trees that make up the forest canopy. Thus, the evolution of larger sieve plate pores in canopy-dominant trees may have played a key role in allowing woody angiosperms to extend beyond their understory origins.
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Affiliation(s)
- Juan M Losada
- Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA, 02138, USA
- Arnold Arboretum of Harvard University, 1300 Centre St., Boston, MA, 02130, USA
| | - N Michele Holbrook
- Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA, 02138, USA
- Arnold Arboretum of Harvard University, 1300 Centre St., Boston, MA, 02130, USA
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Lazzarin M, Zweifel R, Anten N, Sterck FJ. Does phloem osmolality affect diurnal diameter changes of twigs but not of stems in Scots pine? Tree Physiol 2019; 39:275-283. [PMID: 30371898 DOI: 10.1093/treephys/tpy121] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Revised: 09/12/2018] [Accepted: 10/08/2018] [Indexed: 06/08/2023]
Abstract
Diel stem diameter changes measured at the stem base of temperate tree species can be mostly explained by a hydraulic system of flow and storage compartments passively driven by transpiration. Active, osmotic processes are considered to play a minor role only. Here we explore whether such osmotic processes have a stronger impact on diel changes in twig diameter than in stem diameter because twigs are closer to the leaves, the main source of newly acquired carbon. We investigated stem and twig diameter changes of wood and bark of pine trees in parallel to fluctuations of the osmolality in needles and in the bark at the stem base. We found consistent twig bark size increments concurrent with twig wood size decreases during daylight hours whereas needle osmolality was not consistently increasing even on sunny days. The size changes of bark and wood either reversed or ran in parallel from late afternoon onwards until the next morning. No such patterns were measurable at the stem base. Stem wood was hardly changing in size, whereas stem bark followed the regular pattern of a decrease during the daylight hours and an increase during the night. Osmolality at the stem base showed no particular course over 24 h. We conclude that assimilates from the needles were rapidly transported to the twigs where they increased the osmolality of the bark tissue by sugar loading, explaining the bark size increase (over-) compensating the xylem size decrease. The stem base largely followed the expectation of a passive, hydraulic system without a measurable role of osmoregulation. Diameter changes thus follow different diurnal dynamics in twigs and at the stem base.
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Affiliation(s)
- Martina Lazzarin
- Forest Ecology and Forest Management Group, Wageningen, The Netherlands
| | - Roman Zweifel
- Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) Zürcherstrasse 111, Birmensdorf, Switzerland
| | - Niels Anten
- Centre for Crop Systems Analysis, 6708PB Wageningen, The Netherlands
| | - Frank J Sterck
- Forest Ecology and Forest Management Group, Wageningen, The Netherlands
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Kono Y, Ishida A, Saiki ST, Yoshimura K, Dannoura M, Yazaki K, Kimura F, Yoshimura J, Aikawa SI. Initial hydraulic failure followed by late-stage carbon starvation leads to drought-induced death in the tree Trema orientalis. Commun Biol 2019; 2:8. [PMID: 30623104 PMCID: PMC6323055 DOI: 10.1038/s42003-018-0256-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Accepted: 12/07/2018] [Indexed: 11/09/2022] Open
Abstract
Drought-induced tree death has become a serious problem in global forest ecosystems. Two nonexclusive hypotheses, hydraulic failure and carbon starvation, have been proposed to explain tree die-offs. To clarify the mechanisms, we investigated the physiological processes of drought-induced tree death in saplings with contrasting Huber values (sapwood area/total leaf area). First, hydraulic failure and reduced respiration were found in the initial process of tree decline, and in the last stage carbon starvation led to tree death. The carbohydrate reserves at the stem bases, low in healthy trees, accumulated at the beginning of the declining process due to phloem transport failure, and then decreased just before dying. The concentrations of non-structural carbohydrates at the stem bases are a good indicator of tree damage. The physiological processes and carbon sink-source dynamics that occur during lethal drought provide important insights into the adaptive measures underlying forest die-offs under global warming conditions.
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Affiliation(s)
- Yuri Kono
- Center for Ecological Research, Kyoto University, Otsu, Shiga 520-2113 Japan
| | - Atsushi Ishida
- Center for Ecological Research, Kyoto University, Otsu, Shiga 520-2113 Japan
| | - Shin-Taro Saiki
- Center for Ecological Research, Kyoto University, Otsu, Shiga 520-2113 Japan
- Forestry and Forest Products Research Institute, Tsukuba, Ibaraki 305-8687 Japan
| | - Kenichi Yoshimura
- Faculty of Agriculture, Yamagata University, Tsuruoka, Yamagata 997-8555 Japan
| | - Masako Dannoura
- Kyoto University Graduate School of Global Environmental Studies, Kyoto, Kyoto 606-8502 Japan
- Faculty of Agriculture, Kyoto University, Kyoto, Kyoto 606-8502 Japan
| | - Kenichi Yazaki
- Forestry and Forest Products Research Institute, Tsukuba, Ibaraki 305-8687 Japan
| | - Fuku Kimura
- Graduate School of Bioresource Sciences, Nihon University, Fujisawa, Kanagawa 252-0880 Japan
| | - Jin Yoshimura
- Graduate School of Science and Technology and Department of Mathematical and Systems Engineering, Shizuoka University, Naka-Ku, Hamamatsu Shizuoka, 432-8561 Japan
- Department of Environmental and Forest Biology, State University of New York College of Environmental Science and Forestry, Syracuse, NY 13210 USA
- Marine Biosystems Research Center, Chiba University, Kamogawa, Chiba 299-5502 Japan
| | - Shin-ichi Aikawa
- Japan Forest Technology Association, Chiyoda, Tokyo 102-5281 Japan
- Graduate School of Science and Engineering, Tokyo Metropolitan University, Minami-Osawa, Hachioji, Tokyo 192-0397 Japan
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Jensen KH. Modeling the Hydraulic Conductivity of Phloem Sieve Elements. Methods Mol Biol 2019; 2014:339-344. [PMID: 31197807 DOI: 10.1007/978-1-4939-9562-2_26] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Phloem transport of photoassimilates affects nearly all aspects of plant life, from growth to reproduction. This chapter summarizes mathematical techniques to quantify the impact of sieve element anatomy on phloem transport processes.
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Affiliation(s)
- Kaare H Jensen
- Department of Physics, Technical University of Denmark, Kgs. Lyngby, Denmark.
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Jakobs R, Schweiger R, Müller C. Aphid infestation leads to plant part-specific changes in phloem sap chemistry, which may indicate niche construction. New Phytol 2019; 221:503-514. [PMID: 30040116 DOI: 10.1111/nph.15335] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Accepted: 06/11/2018] [Indexed: 05/15/2023]
Abstract
Phloem sap quality can differ between and within plants, and affect the performance of aphids. In turn, aphid infestation may change the chemical composition and nutritional value of phloem sap. However, the effects of different aphid species on the overall phloem sap composition of distinct parts within plant individuals in relation to aphid performance remain unclear. To test the specificity of plant responses to aphids, we used two chemotypes of Tanacetum vulgare plants and placed the monophagous aphids Macrosiphoniella tanacetaria and Uroleucon tanaceti on different plant parts (stems close to the inflorescence, young and old leaves). Aphid population growth was determined and sugars, organic acids, amino acids and metabolic fingerprints of phloem exudates were analysed. Macrosiphoniella tanacetaria performed best on stems, whereas U. tanaceti performed best on old leaves, indicating differences in niche conformance. Aphid infestation led to distinct changes in the phloem exudate composition of distinct metabolite classes, differing particularly between plant parts but less between chemotypes. In summary, plant responses to aphids are highly specific for the chemotype, plant part, metabolite class and aphid species. These changes may indicate that aphids construct their own niche, optimizing the food quality on the plant parts they prefer.
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Affiliation(s)
- Ruth Jakobs
- Department of Chemical Ecology, Bielefeld University, Universitätsstr. 25, Bielefeld, 33615, Germany
| | - Rabea Schweiger
- Department of Chemical Ecology, Bielefeld University, Universitätsstr. 25, Bielefeld, 33615, Germany
| | - Caroline Müller
- Department of Chemical Ecology, Bielefeld University, Universitätsstr. 25, Bielefeld, 33615, Germany
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Henriksson N, Rademacher TT. Stem Compression: A Means to Reversibly Reduce Phloem Transport in Tree Stems. Methods Mol Biol 2019; 2014:301-310. [PMID: 31197805 DOI: 10.1007/978-1-4939-9562-2_24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Stem compression reduces or terminates the phloem-mediated transport of carbohydrates and other solutes in tree stems, without causing permanent damage to phloem functioning (Henriksson et al. Tree Physiol. 35:1075-1085, 2015). This has been tested on two species of pine trees, with diameters ranging from 3 to 26 cm in a forest in northern Sweden (Henriksson et al. Tree Physiol. 35:1075-1085, 2015) and in Harvard Forest, USA. Halting the phloem transport of trees in a forest is useful for studying tree physiological processes related to, or dependent on, phloem-transported compounds as well as downstream processes, in particular interactions with soil microbes. Phloem compression can be deployed in the lab and field on single trees, subsets, or over larger areas, depending on what is relevant for a particular research question.
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Affiliation(s)
- Nils Henriksson
- Department of Forest Ecology and Management, Swedish University of Agriculture (SLU), Umeå, Sweden.
| | - Tim T Rademacher
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, USA
- School of Informatics, Computing & Cyber Systems, Northern Arizona University, Flagstaff, AZ, USA
- Center for Ecosystem Science and Society, Northern Arizona University, Flagstaff, AZ, USA
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42
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Clair B, Ghislain B, Prunier J, Lehnebach R, Beauchêne J, Alméras T. Mechanical contribution of secondary phloem to postural control in trees: the bark side of the force. New Phytol 2019; 221:209-217. [PMID: 30076782 DOI: 10.1111/nph.15375] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 07/01/2018] [Indexed: 06/08/2023]
Abstract
To grow straight, plants need a motor system that controls posture by generating forces to offset gravity. This motor function in trees was long thought to be only controlled by internal forces induced in wood. Here we provide evidence that bark is involved in the generation of mechanical stresses in several tree species. Saplings of nine tropical species were grown tilted and staked in a shadehouse and the change in curvature of the stem was measured after releasing from the pole and after removing the bark. This first experiment evidenced the contribution of bark in the up-righting movement of tree stems. Combined mechanical measurements of released strains on adult trees and microstructural observations in both transverse and longitudinal/tangential plane enabled us to identify the mechanism responsible for the development of asymmetric mechanical stress in the bark of stems of these species. This mechanism does not result from cell wall maturation like in wood, or from the direct action of turgor pressure like in unlignified organs, but is the consequence of the interaction between wood radial pressure and a smartly organized trellis structure in the inner bark.
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Affiliation(s)
- Bruno Clair
- CNRS, UMR Ecologie des Forêts de Guyane (EcoFoG), AgroParisTech, CIRAD, INRA, Université des Antilles, Université de Guyane, 97310, Kourou, France
| | - Barbara Ghislain
- CNRS, UMR Ecologie des Forêts de Guyane (EcoFoG), AgroParisTech, CIRAD, INRA, Université des Antilles, Université de Guyane, 97310, Kourou, France
| | - Jonathan Prunier
- CNRS, UMR Ecologie des Forêts de Guyane (EcoFoG), AgroParisTech, CIRAD, INRA, Université des Antilles, Université de Guyane, 97310, Kourou, France
| | - Romain Lehnebach
- CNRS, UMR Ecologie des Forêts de Guyane (EcoFoG), AgroParisTech, CIRAD, INRA, Université des Antilles, Université de Guyane, 97310, Kourou, France
- LMGC, CNRS, Université de Montpellier, 34090, Montpellier, France
| | - Jacques Beauchêne
- CIRAD, UMR Ecologie des Forêts de Guyane (EcoFoG), AgroParisTech, CNRS, INRA, Université des Antilles, Université de Guyane, 97310, Kourou, France
| | - Tancrède Alméras
- LMGC, CNRS, Université de Montpellier, 34090, Montpellier, France
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Garzo E, Fernández-Pascual M, Morcillo C, Fereres A, Gómez-Guillamón ML, Tjallingii WF. Ultrastructure of compatible and incompatible interactions in phloem sieve elements during the stylet penetration by cotton aphids in melon. Insect Sci 2018; 25:631-642. [PMID: 28213963 DOI: 10.1111/1744-7917.12447] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 01/09/2017] [Accepted: 01/23/2017] [Indexed: 05/23/2023]
Abstract
Resistance of the melon line TGR-1551 to the aphid Aphis gossypii is based on preventing aphids from ingesting phloem sap. In electrical penetration graphs (EPGs), this resistance has been characterized with A. gossypii showing unusually long phloem salivation periods (waveform E1) mostly followed by pathway activities (waveform C) or if followed by phloem ingestion (waveform E2), ingestion was not sustained for more than 10 min. Stylectomy with aphids on susceptible and resistant plants was performed during EPG recording while the stylet tips were phloem inserted. This was followed by dissection of the penetrated leaf section, plant tissue fixation, resin embedding, and ultrathin sectioning for transmission electron microscopic observation in order to study the resistance mechanism in the TGR. The most obvious aspect appeared to be the coagulation of phloem proteins inside the stylet canals and the punctured sieve elements. Stylets of 5 aphids per genotype were amputated during sieve element (SE) salivation (E1) and SE ingestion (E2). Cross-sections of stylet bundles in susceptible melon plants showed that the contents of the stylet canals were totally clear and also, no coagulated phloem proteins occurred in their punctured sieve elements. In contrast, electron-dense coagulations were found in both locations in the resistant plants. Due to calcium binding, aphid saliva has been hypothesized to play an essential role in preventing/suppressing such coagulations that cause occlusion of sieves plate and in the food canal of the aphid's stylets. Doubts about this role of E1 salivation are discussed on the basis of our results.
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Affiliation(s)
- Elisa Garzo
- Instituto de Ciencias Agrarias, Consejo Superior de Investigaciones Científicas (ICA-CSIC), Madrid, Spain
- Laboratory of Entomology, Wageningen University, Wageningen, the Netherlands
| | - Mercedes Fernández-Pascual
- Instituto de Ciencias Agrarias, Consejo Superior de Investigaciones Científicas (ICA-CSIC), Madrid, Spain
| | - Cesar Morcillo
- Instituto de Ciencias Agrarias, Consejo Superior de Investigaciones Científicas (ICA-CSIC), Madrid, Spain
| | - Alberto Fereres
- Instituto de Ciencias Agrarias, Consejo Superior de Investigaciones Científicas (ICA-CSIC), Madrid, Spain
| | - M Luisa Gómez-Guillamón
- Instituto de Hortofruticultura Subtropical y Mediterránea "La Mayora", Universidad de Málaga-CSIC (IHSM-UMA-CSIC), Algarrobo-Costa, Málaga, Spain
| | - W Fred Tjallingii
- Laboratory of Entomology, Wageningen University, Wageningen, the Netherlands
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Sevanto S, Ryan M, Dickman LT, Derome D, Patera A, Defraeye T, Pangle RE, Hudson PJ, Pockman WT. Is desiccation tolerance and avoidance reflected in xylem and phloem anatomy of two coexisting arid-zone coniferous trees? Plant Cell Environ 2018; 41:1551-1564. [PMID: 29569276 DOI: 10.1111/pce.13198] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 02/28/2018] [Accepted: 03/06/2018] [Indexed: 06/08/2023]
Abstract
Plants close their stomata during drought to avoid excessive water loss, but species differ in respect to the drought severity at which stomata close. The stomatal closure point is related to xylem anatomy and vulnerability to embolism, but it also has implications for phloem transport and possibly phloem anatomy to allow sugar transport at low water potentials. Desiccation-tolerant plants that close their stomata at severe drought should have smaller xylem conduits and/or fewer and smaller interconduit pits to reduce vulnerability to embolism but more phloem tissue and larger phloem conduits compared with plants that avoid desiccation. These anatomical differences could be expected to increase in response to long-term reduction in precipitation. To test these hypotheses, we used tridimensional synchroton X-ray microtomograph and light microscope imaging of combined xylem and phloem tissues of 2 coniferous species: one-seed juniper (Juniperus monosperma) and piñon pine (Pinus edulis) subjected to precipitation manipulation treatments. These species show different xylem vulnerability to embolism, contrasting desiccation tolerance, and stomatal closure points. Our results support the hypothesis that desiccation tolerant plants require higher phloem transport capacity than desiccation avoiding plants, but this can be gained through various anatomical adaptations in addition to changing conduit or tissue size.
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Affiliation(s)
- Sanna Sevanto
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, Bikini Atoll Road MS J535, Los Alamos, NM, 87545, USA
| | - Max Ryan
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, Bikini Atoll Road MS J535, Los Alamos, NM, 87545, USA
| | - L Turin Dickman
- Earth and Environmental Sciences Division, Los Alamos National Laboratory, Bikini Atoll Road MS J535, Los Alamos, NM, 87545, USA
| | - Dominique Derome
- Laboratory for Multiscale Studies in Building Physics, Swiss Federal Laboratories for Material Science and Technology (Empa), Ueberlandstrasse 129, 8600, Duebendorf, Switzerland
| | - Alessandra Patera
- Swiss Light Source, Paul Scherrer Institute, 5232, Villigen, Switzerland
- Centre d'Imagerie BioMedicale, Ecole Polytechnique Federale de Lausanne, 1015, Lausanne, Switzerland
| | - Thijs Defraeye
- Laboratory for Multiscale Studies in Building Physics, Swiss Federal Laboratories for Material Science and Technology (Empa), Ueberlandstrasse 129, 8600, Duebendorf, Switzerland
- Chair of Building Physics, ETH Zurich, Stefano-Franscini-Platz 5, 8093, Zurich, Switzerland
| | - Robert E Pangle
- Department of Biology, University of New Mexico, Castetter Hall 1480, Yale Boulevard NE, Albuquerque, NM, 87131, USA
| | - Patrick J Hudson
- Department of Biology, University of New Mexico, Castetter Hall 1480, Yale Boulevard NE, Albuquerque, NM, 87131, USA
| | - William T Pockman
- Department of Biology, University of New Mexico, Castetter Hall 1480, Yale Boulevard NE, Albuquerque, NM, 87131, USA
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45
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Sun M, Voorrips RE, Steenhuis-Broers G, van’t Westende W, Vosman B. Reduced phloem uptake of Myzus persicae on an aphid resistant pepper accession. BMC Plant Biol 2018; 18:138. [PMID: 29945550 PMCID: PMC6020309 DOI: 10.1186/s12870-018-1340-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 06/04/2018] [Indexed: 05/24/2023]
Abstract
BACKGROUND The green peach aphid (GPA), Myzus persicae, is economically one of the most threatening pests in pepper cultivation, which not only causes direct damage but also transmits many viruses. Breeding aphid resistant pepper varieties is a promising and environmentally friendly method to control aphid populations in the field and in the greenhouse. Until now, no strong sources of resistance against the GPA have been identified. Therefore the main aims of this study were to identify pepper materials with a good level of resistance to GPA and to elucidate possible resistance mechanisms. RESULTS We screened 74 pepper accessions from different geographical areas for resistance to M. persicae. After four rounds of evaluation we identified one Capsicum baccatum accession (PB2013071) as highly resistant to M. persicae, while the accessions PB2013062 and PB2012022 showed intermediate resistance. The resistance of PB2013071 resulted in a severely reduced uptake of phloem compared to the susceptible accession, as determined by Electrical Penetration Graph (EPG) studies. Feeding of M. persicae induced the expression of callose synthase genes and resulted in callose deposition in the sieve elements in resistant, but not in susceptible plants. CONCLUSIONS Three aphid resistant pepper accessions were identified, which will be important for breeding aphid resistant pepper varieties in the future. The most resistant accession PB2013071 showed phloem-based resistance against aphid infestation.
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Affiliation(s)
- Mengjing Sun
- Plant Breeding, Wageningen University & Research, P.O. Box 386, 6700 AJ Wageningen, The Netherlands
| | - Roeland E. Voorrips
- Plant Breeding, Wageningen University & Research, P.O. Box 386, 6700 AJ Wageningen, The Netherlands
| | - Greet Steenhuis-Broers
- Plant Breeding, Wageningen University & Research, P.O. Box 386, 6700 AJ Wageningen, The Netherlands
| | - Wendy van’t Westende
- Plant Breeding, Wageningen University & Research, P.O. Box 386, 6700 AJ Wageningen, The Netherlands
| | - Ben Vosman
- Plant Breeding, Wageningen University & Research, P.O. Box 386, 6700 AJ Wageningen, The Netherlands
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Abstract
PREMISE OF THE STUDY While tradeoffs among mechanical and conductive functions have been well investigated in woody stems, these tradeoffs are relatively unexplored in petioles, the structural link between stems and laminas. We investigated size-independent scaling relationships between cross-sectional areas of structural and vascular tissues, relationships between tissue areas of xylem and phloem, vessel packing within xylem, and scaling of vascular and structural tissues with lamina traits. METHODS We examined allometric relationships among petiole tissues and as a function of lamina and petiole size variation on eleven species of Pelargonium. From transverse sections of methacrylate-embedded tissue, we measured the cross-sectional areas of all tissues within the petiole and vessel lumen, and cell wall areas of each vessel. Allometric scaling relationships were analyzed using standardized major axis regressions. KEY RESULTS Pelargonium petiole vessels were packed as predicted by Sperry's packing rule for woody stems. In contrast to woody stems, there was no evidence of a tradeoff between vessel area and fiber area. Within cross-sections, more xylem was produced than phloem. Among bundles, xylem and phloem scaling relationships varied with bundle position. Except for lamina dry mass and petiole fiber cross-sectional area, petiole and lamina traits were independent. CONCLUSIONS Petioles share vascular tissue traits with stems despite derivation from leaf primordia. We did not find evidence for a tradeoff between structural and vascular tissues, in part because fibers occur outside the xylem. We propose this separation of conduction and support underlies observed developmental and evolutionary plasticity in petioles.
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Affiliation(s)
- Dustin M Ray
- University of Connecticut, Ecology and Evolutionary Biology Department, 75 N. Eagleville Road, Unit 3043, Storrs, ConnecticutT, 06269, U.S.A
| | - Cynthia S Jones
- University of Connecticut, Ecology and Evolutionary Biology Department, 75 N. Eagleville Road, Unit 3043, Storrs, ConnecticutT, 06269, U.S.A
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Wu ZC, Zhang JQ, Zhao JT, Li JG, Huang XM, Wang HC. Biosynthesis of quebrachitol, a transportable photosynthate, in Litchi chinensis. J Exp Bot 2018; 69:1649-1661. [PMID: 29281092 PMCID: PMC5889025 DOI: 10.1093/jxb/erx483] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2017] [Accepted: 12/15/2017] [Indexed: 05/31/2023]
Abstract
Although methylated cyclitols constitute a major proportion of the carbohydrates in many plant species, their physiological roles and biosynthetic pathway are largely unknown. Quebrachitol (2-O-methyl-chiro-inositol) is one of the major methylated cyclitols in some plant species. In litchi, quebrachitol represents approximately 50% of soluble sugars in mature leaves and 40% of the total sugars in phloem exudate. In the present study, we identified bornesitol as a transient methylated intermediate of quebrachitol and measured the concentrations of methyl-inositols in different tissues and in tissues subjected to different treatments. 14CO2 feeding and phloem exudate experiments demonstrated that quebrachitol is one of the transportable photosynthates. In contrast to other plant species, the biosynthesis of quebrachitol in litchi is not associated with osmotic stress. High quebrachitol concentrations in tissues of the woody plant litchi might represent a unique carbon metabolic strategy that maintains osmolality under reduced-sucrose conditions. The presence of bornesitol but not ononitol in the leaves indicates a different biosynthetic pathway with pinitol. The biosynthesis of quebrachitol involves the methylation of myo-inositol and the subsequent epimerization of bornesitol. An inositol methyltransferase gene (LcIMT1) responsible for bornesitol biosynthesis was isolated and characterized for the first time, and the biosynthesis pathways of methyl-inositols are discussed.
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Affiliation(s)
- Zi-Chen Wu
- Guangdong Litchi Engineering Research Center, College of Horticulture, South China Agricultural University, Guangzhou, China
| | - Jie-Qiong Zhang
- Guangdong Litchi Engineering Research Center, College of Horticulture, South China Agricultural University, Guangzhou, China
| | - Jie-Tang Zhao
- Guangdong Litchi Engineering Research Center, College of Horticulture, South China Agricultural University, Guangzhou, China
| | - Jian-Guo Li
- Guangdong Litchi Engineering Research Center, College of Horticulture, South China Agricultural University, Guangzhou, China
| | - Xu-Ming Huang
- Guangdong Litchi Engineering Research Center, College of Horticulture, South China Agricultural University, Guangzhou, China
| | - Hui-Cong Wang
- Guangdong Litchi Engineering Research Center, College of Horticulture, South China Agricultural University, Guangzhou, China
- Department of Life Sciences and Technology, Yangtze Normal University, Fuling, China
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Takahashi H, Xiaohua Q, Shimamura S, Yanagawa A, Hiraga S, Nakazono M. Sucrose supply from leaves is required for aerenchymatous phellem formation in hypocotyl of soybean under waterlogged conditions. Ann Bot 2018; 121:723-732. [PMID: 29370345 PMCID: PMC5853023 DOI: 10.1093/aob/mcx205] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Accepted: 12/12/2017] [Indexed: 05/21/2023]
Abstract
Background and Aims Soil waterlogging often causes oxygen deficiency in the root systems of plants and severely inhibits plant growth. Formation of aerenchyma - interconnected spaces that facilitate the movement of gases between and within the aerial and submerged parts of plants - is an adaptive trait for coping with waterlogged conditions. Soybean (Glycine max) forms porous secondary tissues known as aerenchymatous phellem (AP), which are derived from the outermost cell layer of phellogen. To understand what factors other than waterlogging are involved in phellogen and AP formation, we examined how their formation in soybean seedlings was affected by darkness, CO2 deficiency and blockage of phloem transport. Methods Aerenchymatous phellem and phellogen formation were expressed as area ratios in cross-sections of hypocotyl. CO2 was depleted by use of calcium oxide and sodium hydroxide. Phloem transport was blocked by heat-girdling of hypocotyls. Sucrose levels were measured by spectrophotometry. Key Results Under light conditions, waterlogging induced the accumulation of high concentrations of sucrose in hypocotyls, followed by phellogen and AP formation in hypocotyls. Phellogen formation and AP formation were inhibited by darkness, CO2 deficiency and blockage of phloem transport. Phellogen formation and AP formation were also inhibited by excision of shoots above the epicotyl, but they recovered following application of sucrose (but not glucose or fructose application) to the cut surface. Conclusions The results demonstrate that sucrose derived from leaves is essential for AP and phellogen formation in soybean hypocotyls under waterlogged soil conditions. Maintenance of a high sucrose concentration is thus essential for the development of phellogen and AP and the differentiation of phellogen to AP.
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Affiliation(s)
- Hirokazu Takahashi
- Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa, Nagoya, Japan
| | - Qi Xiaohua
- Department of Horticulture, School of Horticulture and Plant Protection, Yangzhou University, Yangzhou, Jiangsu, P.R. China
| | - Satoshi Shimamura
- NARO Tohoku Agricultural Research Center, Kariwano, Daisen, Akita, Japan
| | - Asako Yanagawa
- Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa, Nagoya, Japan
| | - Susumu Hiraga
- NARO Institute of Crop Science, Kannondai, Tsukuba, Ibaraki, Japan
| | - Mikio Nakazono
- Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa, Nagoya, Japan
- School of Plant Biology, The University of Western Australia, Crawley, WA, Australia
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Blob B, Heo JO, Helariutta Y. Phloem differentiation: an integrative model for cell specification. J Plant Res 2018; 131:31-36. [PMID: 29204753 PMCID: PMC5762813 DOI: 10.1007/s10265-017-0999-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 11/18/2017] [Indexed: 05/21/2023]
Abstract
Plant vasculature consists of two major conductive cell types, xylem tracheary elements and phloem sieve elements (SEs). Both cell types undergo a highly specialized differentiation process. The root meristem of Arabidopsis displays a stereotypical anatomy in which the central vasculature is surrounded by concentric layers of outer tissues. Each cell file is derived from stem cells located in the root tip. A series of formative and proliferative divisions take place in the meristem; these are followed by cell expansion and differentiation. Protophloem differentiation is unique in being complete only 20-25 cells away from the first stem cell, and during the differentiation process the cells lose several organelles, including the nucleus, while the remaining organelles are rearranged. Defects in SE development have been shown to result in impaired auxin transport and response and therefore systemically affect root growth. Although a few genes have been demonstrated to function in phloem development, detailed analyses and a comprehensive understanding of sieve element development (i.e. how often the stem cells divide, how frequently enucleation takes place, and how SE development is coordinated between cell division and differentiation on a molecular level) are still lacking. Advanced live-imaging techniques which enable prolonged time-lapse captures of root tip growth as well as single-cell transcriptomic analysis of the 20-25 cells in the SE file could help resolve these questions. In addition, understanding the interplay between the PLETHORA (PLT) gradient, which is known to govern the root zonation, and phloem development within the root meristem could shed light on the rapidity of SE differentiation and its importance to the meristem.
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Affiliation(s)
- Bernhard Blob
- Sainsbury Laboratory, Cambridge University, Bateman Street, Cambridge, CB2 1LR, UK
| | - Jung-Ok Heo
- Sainsbury Laboratory, Cambridge University, Bateman Street, Cambridge, CB2 1LR, UK
- Institute of Biotechnology, University of Helsinki, 00014, Helsinki, Finland
| | - Yka Helariutta
- Sainsbury Laboratory, Cambridge University, Bateman Street, Cambridge, CB2 1LR, UK.
- Institute of Biotechnology, University of Helsinki, 00014, Helsinki, Finland.
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Calvo P, Sahi VP, Trewavas A. Are plants sentient? Plant Cell Environ 2017; 40:2858-2869. [PMID: 28875517 DOI: 10.1111/pce.13065] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Revised: 08/26/2017] [Accepted: 08/27/2017] [Indexed: 05/07/2023]
Abstract
Feelings in humans are mental states representing groups of physiological functions that usually have defined behavioural purposes. Feelings, being evolutionarily ancient, are thought to be coordinated in the brain stem of animals. One function of the brain is to prioritise between competing mental states and, thus, groups of physiological functions and in turn behaviour. Plants use groups of coordinated physiological activities to deal with defined environmental situations but currently have no known mental state to prioritise any order of response. Plants do have a nervous system based on action potentials transmitted along phloem conduits but which in addition, through anastomoses and other cross-links, forms a complex network. The emergent potential for this excitable network to form a mental state is unknown, but it might be used to distinguish between different and even contradictory signals to the individual plant and thus determine a priority of response. This plant nervous system stretches throughout the whole plant providing the potential for assessment in all parts and commensurate with its self-organising, phenotypically plastic behaviour. Plasticity may, in turn, depend heavily on the instructive capabilities of local bioelectric fields enabling both a degree of behavioural independence but influenced by the condition of the whole plant.
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Affiliation(s)
- Paco Calvo
- Institute of Molecular Plant Sciences, University of Edinburgh, Mayfield Road, Edinburgh, EH9 3JH, UK
- Minimal Intelligence Lab, University of Murcia, Murcia, Spain
| | - Vaidurya Pratap Sahi
- Molecular Cell Biology, Karlsruhe Institute of Technology, 76131, Karlsruhe, Germany
| | - Anthony Trewavas
- Institute of Molecular Plant Sciences, University of Edinburgh, Mayfield Road, Edinburgh, EH9 3JH, UK
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