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Cabrita PJV. Water exchange between the Chlorenchyma and the Hydrenchyma and its physiological role in leaves with Crassulacean acid metabolism. PHYSIOLOGIA PLANTARUM 2024; 176:e14221. [PMID: 38450837 DOI: 10.1111/ppl.14221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Accepted: 02/08/2024] [Indexed: 03/08/2024]
Abstract
Direct and non-destructive measurements of plant-water relations of plants exhibiting the Crassulacean acid metabolism (CAM) photosynthetic pathway are seldom addressed, with most findings inferred from gas exchange measurements. The main focus of this paper was to study how the water exchange between the chlorenchyma and the hydrenchyma depends on and follows the CAM photosynthetic diel pattern using non-invasive and continuous methods. Gas exchange and leaf patch clamp pressure probe (LPCP) measurements were performed on Aloe vera (L.) Burm f., a CAM species, and compared to measurements on banana (Musa acuminata Colla), a C3 species. The LPCP output pressure, Pp , of Aloe vera plants follows its diel CAM photosynthetic cycle, reversed to that observed in banana and other C3 species. The four phases of CAM photosynthesis can also be identified in the diel LPCP output pressure, Pp , cycle. The Pp values in Aloe vera are determined by the hydrenchyma turgor pressure, with both parameters being reversely related. A non-invasive and continuous assessment of the water exchange between the chlorenchyma and the hydrenchyma in CAM plants, namely, by following the changes in the hydrenchyma turgor pressure, is presented. However, showing once more how the LPCP output pressure, Pp , depends on the leaf structure, such an approach can be used to study plant-water relations in other CAM species with a leaf structure similar to Aloe vera, with the hydrenchyma composing most of the leaf volume.
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Yamaga-Hatakeyama Y, Okutani M, Hatakeyama Y, Yabiku T, Yukawa T, Ueno O. Photosynthesis and leaf structure of F1 hybrids between Cymbidium ensifolium (C3) and C. bicolor subsp. pubescens (CAM). ANNALS OF BOTANY 2023; 132:895-907. [PMID: 36579478 PMCID: PMC10799985 DOI: 10.1093/aob/mcac157] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 11/17/2022] [Accepted: 12/16/2022] [Indexed: 06/17/2023]
Abstract
BACKGROUND AND AIMS The introduction of crassulacean acid metabolism (CAM) into C3 crops has been considered as a means of improving water-use efficiency. In this study, we investigated photosynthetic and leaf structural traits in F1 hybrids between Cymbidium ensifolium (female C3 parent) and C. bicolor subsp. pubescens (male CAM parent) of the Orchidaceae. METHODS Seven F1 hybrids produced through artificial pollination and in vitro culture were grown in a greenhouse with the parent plants. Structural, biochemical and physiological traits involved in CAM in their leaves were investigated. KEY RESULTS Cymbidium ensifolium accumulated very low levels of malate without diel fluctuation, whereas C. bicolor subsp. pubescens showed nocturnal accumulation and diurnal consumption of malate. The F1s also accumulated malate at night, but much less than C. bicolor subsp. pubescens. This feature was consistent with low nocturnal fixation of atmospheric CO2 in the F1s. The δ13C values of the F1s were intermediate between those of the parents. Leaf thickness was thicker in C. bicolor subsp. pubescens than in C. ensifolium, and those of the F1s were more similar to that of C. ensifolium. This was due to the difference in mesophyll cell size. The chloroplast coverage of mesophyll cell perimeter adjacent to intercellular air spaces of C. bicolor subsp. pubescens was lower than that of C. ensifolium, and that of the F1s was intermediate between them. Interestingly, one F1 had structural and physiological traits more similar to those of C. bicolor subsp. pubescens than the other F1s. Nevertheless, all F1s contained intermediate levels of phosphoenolpyruvate carboxylase but as much pyruvate, Pi dikinase as C. bicolor subsp. pubescens. CONCLUSIONS CAM traits were intricately inherited in the F1 hybrids, the level of CAM expression varied widely among F1 plants, and the CAM traits examined were not necessarily co-ordinately transmitted to the F1s.
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Affiliation(s)
| | - Masamitsu Okutani
- School of Agriculture, Kyushu University, Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Yuto Hatakeyama
- Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Takayuki Yabiku
- Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Tomohisa Yukawa
- Tsukuba Botanical Garden, National Museum of Nature and Science, Tsukuba, Ibaraki 305-0005, Japan
| | - Osamu Ueno
- Faculty of Agriculture, Kyushu University, Motooka, Nishi-ku, Fukuoka 819-0395, Japan
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Leverett A, Borland AM, Inge EJ, Hartzell S. Low internal air space in plants with crassulacean acid metabolism may be an anatomical spandrel. ANNALS OF BOTANY 2023; 132:811-817. [PMID: 37622678 PMCID: PMC10799988 DOI: 10.1093/aob/mcad109] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Revised: 07/19/2023] [Accepted: 08/17/2023] [Indexed: 08/26/2023]
Abstract
Crassulacean acid metabolism (CAM) is a photosynthetic adaptation found in at least 38 plant families. Typically, the anatomy of CAM plants is characterized by large photosynthetic cells and a low percentage of leaf volume consisting of internal air space (% IAS). It has been suggested that reduced mesophyll conductance (gm) arising from low % IAS benefits CAM plants by preventing the movement of CO2 out of cells and ultimately minimizing leakage of CO2 from leaves into the atmosphere during day-time decarboxylation. Here, we propose that low % IAS does not provide any adaptive benefit to CAM plants, because stomatal closure during phase III of CAM will result in internal concentrations of CO2 becoming saturated, meaning low gm will not have any meaningful impact on the flux of gases within leaves. We suggest that low % IAS is more likely an indirect consequence of maximizing the cellular volume within a leaf, to provide space for the overnight storage of malic acid during the CAM cycle.
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Affiliation(s)
- Alistair Leverett
- School of Life Sciences, University of Essex, Wivenhoe Campus, Essex, CO4 3SQ, UK
- Department of Plant Sciences, University of Cambridge, Downing St., Cambridge, CB2 3EA, UK
| | - Anne M Borland
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
| | - Emma J Inge
- School of Life Sciences, University of Essex, Wivenhoe Campus, Essex, CO4 3SQ, UK
| | - Samantha Hartzell
- Department of Civil and Environmental Engineering, Portland State University, 1930 SW 124 Ave., Portland, OR, USA
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Leverett A, Borland AM. Elevated nocturnal respiratory rates in the mitochondria of CAM plants: current knowledge and unanswered questions. ANNALS OF BOTANY 2023; 132:855-867. [PMID: 37638861 PMCID: PMC10799998 DOI: 10.1093/aob/mcad119] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Revised: 07/14/2023] [Accepted: 08/25/2023] [Indexed: 08/29/2023]
Abstract
Crassulacean acid metabolism (CAM) is a metabolic adaptation that has evolved convergently in 38 plant families to aid survival in water-limited niches. Whilst primarily considered a photosynthetic adaptation, CAM also has substantial consequences for nocturnal respiratory metabolism. Here, we outline the history, current state and future of nocturnal respiration research in CAM plants, with a particular focus on the energetics of nocturnal respiratory oxygen consumption. Throughout the 20th century, research interest in nocturnal respiration occurred alongside initial discoveries of CAM, although the energetic and mechanistic implications of nocturnal oxygen consumption and links to the operation of the CAM cycle were not fully understood. Recent flux balance analysis (FBA) models have provided new insights into the role that mitochondria play in the CAM cycle. Several FBA models have predicted that CAM requires elevated nocturnal respiratory rates, compared to C3 species, to power vacuolar malic acid accumulation. We provide physiological data, from the genus Clusia, to corroborate these modelling predictions, thereby reinforcing the importance of elevated nocturnal respiratory rates for CAM. Finally, we outline five unanswered questions pertaining to nocturnal respiration which must be addressed if we are to fully understand and utilize CAM plants in a hotter, drier world.
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Affiliation(s)
- Alistair Leverett
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK
- Department of Plant Sciences, University of Cambridge, Downing St., Cambridge CB2 3EA, UK
| | - Anne M Borland
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
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Sage RF, Edwards EJ, Heyduk K, Cushman JC. Crassulacean acid metabolism (CAM) at the crossroads: a special issue to honour 50 years of CAM research by Klaus Winter. ANNALS OF BOTANY 2023; 132:553-561. [PMID: 37856823 PMCID: PMC10799977 DOI: 10.1093/aob/mcad160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Accepted: 10/18/2023] [Indexed: 10/21/2023]
Affiliation(s)
- Rowan F Sage
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario M5R3C6, Canada
| | - Erika J Edwards
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06511, USA
| | - Karolina Heyduk
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT 06269, USA
| | - John C Cushman
- Department of Biochemistry and Molecular Biology, University of Nevada–Reno, Reno, NV 89557, USA
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Chomthong M, Griffiths H. Prospects and perspectives: inferring physiological and regulatory targets for CAM from molecular and modelling approaches. ANNALS OF BOTANY 2023; 132:583-596. [PMID: 37742290 PMCID: PMC10799989 DOI: 10.1093/aob/mcad142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Revised: 08/26/2023] [Accepted: 09/21/2023] [Indexed: 09/26/2023]
Abstract
BACKGROUND AND SCOPE This review summarizes recent advances in our understanding of Crassulacean Acid Metabolism (CAM) by integrating evolutionary, ecological, physiological, metabolic and molecular perspectives. A number of key control loops which moderate the expression of CAM phases, and their metabolic and molecular control, are explored. These include nocturnal stomatal opening, activation of phosphoenolpyruvate carboxylase by a specific protein kinase, interactions with circadian clock control, as well as daytime decarboxylation and activation of Rubisco. The vacuolar storage and release of malic acid and the interplay between the supply and demand for carbohydrate reserves are also key metabolic control points. FUTURE OPPORTUNITIES We identify open questions and opportunities, with experimentation informed by top-down molecular modelling approaches allied with bottom-up mechanistic modelling systems. For example, mining transcriptomic datasets using high-speed systems approaches will help to identify targets for future genetic manipulation experiments to define the regulation of CAM (whether circadian or metabolic control). We emphasize that inferences arising from computational approaches or advanced nuclear sequencing techniques can identify potential genes and transcription factors as regulatory targets. However, these outputs then require systematic evaluation, using genetic manipulation in key model organisms over a developmental progression, combining gene silencing and metabolic flux analysis and modelling to define functionality across the CAM day-night cycle. From an evolutionary perspective, the origins and function of CAM succulents and responses to water deficits are set against the mesophyll and hydraulic limitations imposed by cell and tissue succulence in contrasting morphological lineages. We highlight the interplay between traits across shoots (3D vein density, mesophyll conductance and cell shrinkage) and roots (xylem embolism and segmentation). Thus, molecular, biophysical and biochemical processes help to curtail water losses and exploit rapid rehydration during restorative rain events. In the face of a changing climate, we hope such approaches will stimulate opportunities for future research.
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Affiliation(s)
- Methawi Chomthong
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK
| | - Howard Griffiths
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK
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Mok D, Leung A, Searles P, Sage TL, Sage RF. CAM photosynthesis in Bulnesia retama (Zygophyllaceae), a non-succulent desert shrub from South America. ANNALS OF BOTANY 2023; 132:655-670. [PMID: 37625031 PMCID: PMC10799978 DOI: 10.1093/aob/mcad114] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 07/19/2023] [Accepted: 08/23/2023] [Indexed: 08/27/2023]
Abstract
BACKGROUND AND AIMS Bulnesia retama is a drought-deciduous, xerophytic shrub from arid landscapes of South America. In a survey of carbon isotope ratios (δ13C) in specimens from the field, B. retama exhibited less negative values, indicative of CAM or C4 photosynthesis. Here, we investigate whether B. retama is a C4 or CAM plant. METHODS Gas-exchange responses to intercellular CO2, diurnal gas-exchange profiles, δ13C and dawn vs. afternoon titratable acidity were measured on leaves and stems of watered and droughted B. retama plants. Leaf and stem cross-sections were imaged to determine whether the tissues exhibited succulent CAM or C4 Kranz anatomy. KEY RESULTS Field-collected stems and fruits of B. retama exhibited δ13C between -16 and -19 ‰. Plants grown in a glasshouse from field-collected seeds had leaf δ13C values near -31 ‰ and stem δ13C values near -28 ‰. The CO2 response of photosynthesis showed that leaves and stems used C3 photosynthesis during the day, while curvature in the nocturnal response of net CO2 assimilation rate (A) in all stems, coupled with slightly positive rates of A at night, indicated modest CAM function. C4 photosynthesis was absent. Succulence was absent in all tissues, although stems exhibited tight packing of the cortical chlorenchyma in a CAM-like manner. Tissue titratable acidity increased at night in droughted stems. CONCLUSIONS Bulnesia retama is a weak to modest C3 + CAM plant. This is the first report of CAM in the Zygophyllaceae and the first showing that non-succulent, xerophytic shrubs use CAM. CAM alone in B. retama was too limited to explain less negative δ13C in field-collected plants, but combined with effects of low stomatal and mesophyll conductance it could raise δ13C to observed values between -16 and -19 ‰. Modest CAM activity, particularly during severe drought, could enable B. retama to persist in arid habitats of South America.
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Affiliation(s)
- Daniel Mok
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Wilcocks Street, Toronto, Ontario M5R3C6, Canada
| | - Arthur Leung
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Wilcocks Street, Toronto, Ontario M5R3C6, Canada
| | - Peter Searles
- Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja (CRILAR-CONICET), Entre Ríos y Mendoza s/n, Anillaco (5301), La Rioja, Argentina
| | - Tammy L Sage
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Wilcocks Street, Toronto, Ontario M5R3C6, Canada
| | - Rowan F Sage
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Wilcocks Street, Toronto, Ontario M5R3C6, Canada
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Leverett A, Ferguson K, Winter K, Borland AM. Leaf vein density correlates with crassulacean acid metabolism, but not hydraulic capacitance, in the genus Clusia. ANNALS OF BOTANY 2023; 132:801-810. [PMID: 36821473 PMCID: PMC10799986 DOI: 10.1093/aob/mcad035] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 01/26/2023] [Accepted: 02/21/2023] [Indexed: 06/18/2023]
Abstract
BACKGROUND AND AIMS Many succulent species are characterized by the presence of Crassulacean acid metabolism (CAM) and/or elevated bulk hydraulic capacitance (CFT). Both CAM and elevated CFT substantially reduce the rate at which water moves through transpiring leaves. However, little is known about how these physiological adaptations are coordinated with leaf vascular architecture. METHODS The genus Clusia contains species spanning the entire C3-CAM continuum, and also is known to have >5-fold interspecific variation in CFT. We used this highly diverse genus to explore how interspecific variation in leaf vein density is coordinated with CAM and CFT. KEY RESULTS We found that constitutive CAM phenotypes were associated with lower vein length per leaf area (VLA) and vein termini density (VTD), compared to C3 or facultative CAM species. However, when vein densities were standardized by leaf thickness, this value was higher in CAM than C3 species, which is probably an adaptation to overcome apoplastic hydraulic resistance in deep chlorenchyma tissue. In contrast, CFT did not correlate with any xylem anatomical trait measured, suggesting CAM has a greater impact on leaf transpiration rates than CFT. CONCLUSIONS Our findings strongly suggest that CAM photosynthesis is coordinated with leaf vein densities. The link between CAM and vascular anatomy will be important to consider when attempting to bioengineer CAM into C3 crops.
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Affiliation(s)
- Alistair Leverett
- School of Natural and Environmental Sciences, Newcastle University, Newcastle Upon Tyne, NE1 7RU, UK
- Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panama
- School of Life Sciences, University of Essex, Colchester Campus, Colchester, CO4 3SQ, UK
| | - Kate Ferguson
- School of Natural and Environmental Sciences, Newcastle University, Newcastle Upon Tyne, NE1 7RU, UK
| | - Klaus Winter
- Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panama
| | - Anne M Borland
- School of Natural and Environmental Sciences, Newcastle University, Newcastle Upon Tyne, NE1 7RU, UK
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Sage RF, Gilman IS, Smith JAC, Silvera K, Edwards EJ. Atmospheric CO2 decline and the timing of CAM plant evolution. ANNALS OF BOTANY 2023; 132:753-770. [PMID: 37642245 PMCID: PMC10799994 DOI: 10.1093/aob/mcad122] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 08/19/2023] [Accepted: 08/28/2023] [Indexed: 08/31/2023]
Abstract
BACKGROUND AND AIMS CAM photosynthesis is hypothesized to have evolved in atmospheres of low CO2 concentration in recent geological time because of its ability to concentrate CO2 around Rubisco and boost water use efficiency relative to C3 photosynthesis. We assess this hypothesis by compiling estimates of when CAM clades arose using phylogenetic chronograms for 73 CAM clades. We further consider evidence of how atmospheric CO2 affects CAM relative to C3 photosynthesis. RESULTS Where CAM origins can be inferred, strong CAM is estimated to have appeared in the past 30 million years in 46 of 48 examined clades, after atmospheric CO2 had declined from high (near 800 ppm) to lower (<450 ppm) values. In turn, 21 of 25 clades containing CAM species (but where CAM origins are less certain) also arose in the past 30 million years. In these clades, CAM is probably younger than the clade origin. We found evidence for repeated weak CAM evolution during the higher CO2 conditions before 30 million years ago, and possible strong CAM origins in the Crassulaceae during the Cretaceous period prior to atmospheric CO2 decline. Most CAM-specific clades arose in the past 15 million years, in a similar pattern observed for origins of C4 clades. CONCLUSIONS The evidence indicates strong CAM repeatedly evolved in reduced CO2 conditions of the past 30 million years. Weaker CAM can pre-date low CO2 and, in the Crassulaceae, strong CAM may also have arisen in water-limited microsites under relatively high CO2. Experimental evidence from extant CAM species demonstrates that elevated CO2 reduces the importance of nocturnal CO2 fixation by increasing the contribution of C3 photosynthesis to daily carbon gain. Thus, the advantage of strong CAM would be reduced in high CO2, such that its evolution appears less likely and restricted to more extreme environments than possible in low CO2.
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Affiliation(s)
- Rowan F Sage
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, ON, M5S 3B2, Canada
| | - Ian S Gilman
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06511, USA
| | - J Andrew C Smith
- Department of Biology, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
| | - Katia Silvera
- Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA
| | - Erika J Edwards
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06511, USA
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Leverett A, Hartzell S, Winter K, Garcia M, Aranda J, Virgo A, Smith A, Focht P, Rasmussen-Arda A, Willats WGT, Cowan-Turner D, Borland AM. Dissecting succulence: Crassulacean acid metabolism and hydraulic capacitance are independent adaptations in Clusia leaves. PLANT, CELL & ENVIRONMENT 2023; 46:1472-1488. [PMID: 36624682 DOI: 10.1111/pce.14539] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Revised: 01/05/2023] [Accepted: 01/08/2023] [Indexed: 06/17/2023]
Abstract
Succulence is found across the world as an adaptation to water-limited niches. The fleshy organs of succulent plants develop via enlarged photosynthetic chlorenchyma and/or achlorophyllous water storage hydrenchyma cells. The precise mechanism by which anatomical traits contribute to drought tolerance is unclear, as the effect of succulence is multifaceted. Large cells are believed to provide space for nocturnal storage of malic acid fixed by crassulacean acid metabolism (CAM), whilst also buffering water potentials by elevating hydraulic capacitance (CFT ). The effect of CAM and elevated CFT on growth and water conservation have not been compared, despite the assumption that these adaptations often occur together. We assessed the relationship between succulent anatomical adaptations, CAM, and CFT , across the genus Clusia. We also simulated the effects of CAM and CFT on growth and water conservation during drought using the Photo3 model. Within Clusia leaves, CAM and CFT are independent traits: CAM requires large palisade chlorenchyma cells, whereas hydrenchyma tissue governs interspecific differences in CFT . In addition, our model suggests that CAM supersedes CFT as a means to maximise CO2 assimilation and minimise transpiration during drought. Our study challenges the assumption that CAM and CFT are mutually dependent traits within succulent leaves.
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Affiliation(s)
- Alistair Leverett
- School of Natural and Environmental Sciences, Newcastle University, Newcastle Upon Tyne, UK
- Smithsonian Tropical Research Institute, Balboa, Ancón, Republic of Panama
| | - Samantha Hartzell
- Department of Civil and Environmental Engineering, Portland State University, Portland, Oregon, USA
| | - Klaus Winter
- Smithsonian Tropical Research Institute, Balboa, Ancón, Republic of Panama
| | - Milton Garcia
- Smithsonian Tropical Research Institute, Balboa, Ancón, Republic of Panama
| | - Jorge Aranda
- Smithsonian Tropical Research Institute, Balboa, Ancón, Republic of Panama
| | - Aurelio Virgo
- Smithsonian Tropical Research Institute, Balboa, Ancón, Republic of Panama
| | - Abigail Smith
- School of Natural and Environmental Sciences, Newcastle University, Newcastle Upon Tyne, UK
| | - Paulina Focht
- School of Natural and Environmental Sciences, Newcastle University, Newcastle Upon Tyne, UK
| | - Adam Rasmussen-Arda
- School of Natural and Environmental Sciences, Newcastle University, Newcastle Upon Tyne, UK
| | - William G T Willats
- School of Natural and Environmental Sciences, Newcastle University, Newcastle Upon Tyne, UK
| | - Daniel Cowan-Turner
- School of Natural and Environmental Sciences, Newcastle University, Newcastle Upon Tyne, UK
| | - Anne M Borland
- School of Natural and Environmental Sciences, Newcastle University, Newcastle Upon Tyne, UK
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Heyduk K. Evolution of Crassulacean acid metabolism in response to the environment: past, present, and future. PLANT PHYSIOLOGY 2022; 190:19-30. [PMID: 35748752 PMCID: PMC9434201 DOI: 10.1093/plphys/kiac303] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Accepted: 06/07/2022] [Indexed: 06/15/2023]
Abstract
Crassulacean acid metabolism (CAM) is a mode of photosynthesis that evolved in response to decreasing CO2 levels in the atmosphere some 20 million years ago. An elevated ratio of O2 relative to CO2 caused many plants to face increasing stress from photorespiration, a process exacerbated for plants living under high temperatures or in water-limited environments. Today, our climate is again rapidly changing and plants' ability to cope with and adapt to these novel environments is critical for their success. This review focuses on CAM plant responses to abiotic stressors likely to dominate in our changing climate: increasing CO2 levels, increasing temperatures, and greater variability in drought. Empirical studies that have assessed CAM responses are reviewed, though notably these are concentrated in relatively few CAM lineages. Other aspects of CAM biology, including the effects of abiotic stress on the light reactions and the role of leaf succulence, are also considered in the context of climate change. Finally, more recent studies using genomic techniques are discussed to link physiological changes in CAM plants with the underlying molecular mechanism. Together, the body of work reviewed suggests that CAM plants will continue to thrive in certain environments under elevated CO2. However, how CO2 interacts with other environmental factors, how those interactions affect CAM plants, and whether all CAM plants will be equally affected remain outstanding questions regarding the evolution of CAM on a changing planet.
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Bouzroud S, El Maaiden E, Sobeh M, Devkota KP, Boukcim H, Kouisni L, El Kharrassi Y. Micropropagation of Opuntia and Other Cacti Species Through Axillary Shoot Proliferation: A Comprehensive Review. FRONTIERS IN PLANT SCIENCE 2022; 13:926653. [PMID: 35873968 PMCID: PMC9301454 DOI: 10.3389/fpls.2022.926653] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Accepted: 06/08/2022] [Indexed: 06/15/2023]
Abstract
Cacti are one of the most significant and diversified groups of angiosperms, distributed and cultivated globally, mostly in semi-arid, arid, and the Mediterranean climate regions. Conventionally, they are propagated by seeds or through vegetative propagation via rooted offshoots or grafting. However, these multiplication procedures remain insufficient for mass propagation. In vitro culture techniques are utilized to mass propagate endangered and commercial cacti species. These include somatic embryogenesis and plant regeneration through indirect or direct organogenesis. The latter is a promising tool for commercial clonal propagation of high-value species and has been successfully implemented for several species, such as Mammillaria, Hylocereus, Cereus, Echinocereus, and Ariocarpus. However, its success depends on explant type, basal nutrient formulation of culture medium, and types and concentrations of plant growth regulators. This study aimed to assess the potential of in vitro propagation methods applied to cacti species and discuss the different factors affecting the success of these methods. This study has also highlighted the insufficient work on Opuntia species for mass propagation through axillary buds' proliferation. The development of an efficient micropropagation protocol is thus needed to meet the supply of increasing demand of Opuntia species for human consumption as fruit, animal feed, and ecological restoration in semi-arid and arid zones.
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Affiliation(s)
- Sarah Bouzroud
- African Sustainable Agriculture Research Institute (ASARI), Mohammed VI Polytechnic University (UM6P), Laâyoune, Morocco
| | - Ezzouhra El Maaiden
- African Sustainable Agriculture Research Institute (ASARI), Mohammed VI Polytechnic University (UM6P), Laâyoune, Morocco
| | - Mansour Sobeh
- AgroBioSciences Department (AgBS), Mohammed VI Polytechnic University (UM6P), Ben Guerir, Morocco
| | - Krishna Prasad Devkota
- African Sustainable Agriculture Research Institute (ASARI), Mohammed VI Polytechnic University (UM6P), Laâyoune, Morocco
| | - Hassan Boukcim
- AgroBioSciences Department (AgBS), Mohammed VI Polytechnic University (UM6P), Ben Guerir, Morocco
| | - Lamfeddal Kouisni
- African Sustainable Agriculture Research Institute (ASARI), Mohammed VI Polytechnic University (UM6P), Laâyoune, Morocco
| | - Youssef El Kharrassi
- African Sustainable Agriculture Research Institute (ASARI), Mohammed VI Polytechnic University (UM6P), Laâyoune, Morocco
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Fradera-Soler M, Leverett A, Mravec J, Jørgensen B, Borland AM, Grace OM. Are cell wall traits a component of the succulent syndrome? FRONTIERS IN PLANT SCIENCE 2022; 13:1043429. [PMID: 36507451 PMCID: PMC9732111 DOI: 10.3389/fpls.2022.1043429] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Accepted: 10/31/2022] [Indexed: 05/11/2023]
Abstract
Succulence is an adaptation to low water availability characterised by the presence of water-storage tissues that alleviate water stress under low water availability. The succulent syndrome has evolved convergently in over 80 plant families and is associated with anatomical, physiological and biochemical traits. Despite the alleged importance of cell wall traits in drought responses, their significance in the succulent syndrome has long been overlooked. Here, by analyzing published pressure-volume curves, we show that elastic adjustment, whereby plants change cell wall elasticity, is uniquely beneficial to succulents for avoiding turgor loss. In addition, we used comprehensive microarray polymer profiling (CoMPP) to assess the biochemical composition of cell walls in leaves. Across phylogenetically diverse species, we uncover several differences in cell wall biochemistry between succulent and non-succulent leaves, pointing to the existence of a 'succulent glycome'. We also highlight the glycomic diversity among succulent plants, with some glycomic features being restricted to certain succulent lineages. In conclusion, we suggest that cell wall biomechanics and biochemistry should be considered among the characteristic traits that make up the succulent syndrome.
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Affiliation(s)
- Marc Fradera-Soler
- Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg, Denmark
- Department of Accelerated Taxonomy, Royal Botanic Gardens, Kew, Richmond, Surrey, United Kingdom
- *Correspondence: Marc Fradera-Soler, ; Olwen M. Grace,
| | - Alistair Leverett
- School of Natural and Environmental Sciences, Newcastle University, Newcastle Upon Tyne, United Kingdom
- School of Life Sciences, University of Essex, Colchester, United Kingdom
| | - Jozef Mravec
- Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg, Denmark
- Institute of Plant Genetics and Biotechnology, Slovak Academy of Sciences, Plant Science and Biodiversity Center, Nitra, Slovakia
| | - Bodil Jørgensen
- Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg, Denmark
| | - Anne M. Borland
- School of Natural and Environmental Sciences, Newcastle University, Newcastle Upon Tyne, United Kingdom
| | - Olwen M. Grace
- Department of Accelerated Taxonomy, Royal Botanic Gardens, Kew, Richmond, Surrey, United Kingdom
- *Correspondence: Marc Fradera-Soler, ; Olwen M. Grace,
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Leverett A, Hurtado Castaño N, Ferguson K, Winter K, Borland AM. Crassulacean acid metabolism (CAM) supersedes the turgor loss point (TLP) as an important adaptation across a precipitation gradient, in the genus Clusia. FUNCTIONAL PLANT BIOLOGY : FPB 2021; 48:703-716. [PMID: 33663679 DOI: 10.1071/fp20268] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 01/30/2021] [Indexed: 05/25/2023]
Abstract
As future climates continue to change, precipitation deficits are expected to become more severe across tropical ecosystems. As a result, it is important that we identify plant physiological traits that act as adaptations to drought, and determine whether these traits act synergistically or independently of each other. In this study, we assessed the role of three leaf-level putative adaptations to drought: crassulacean acid metabolism (CAM), the turgor loss point (TLPΨ) and water storage hydrenchyma tissue. Using the genus Clusia as a model, we were able to explore the extent to which these leaf physiological traits co-vary, and also how they contribute to species' distributions across a precipitation gradient in Central and South America. We found that CAM is independent of the TLPΨ and hydrenchyma depth in Clusia. In addition, we provide evidence that constitutive CAM is an adaptation to year-long water deficits, whereas facultative CAM appears to be more important for surviving acute dry seasons. Finally, we find that the other leaf traits tested did not correlate with environmental precipitation, suggesting that the reduced transpirational rates associated with CAM obviate the need to adapt the TLPΨ and hydrenchyma depth in this genus.
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Affiliation(s)
- Alistair Leverett
- School of Natural and Environmental Sciences, Newcastle University, Newcastle Upon Tyne, NE1 7RU, UK; and Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panama; and Carl R. Woese Institute for Genomic Biology, 1206 West Gregory Drive, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; and Corresponding author.
| | - Natalia Hurtado Castaño
- School of Natural and Environmental Sciences, Newcastle University, Newcastle Upon Tyne, NE1 7RU, UK; and Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
| | - Kate Ferguson
- School of Natural and Environmental Sciences, Newcastle University, Newcastle Upon Tyne, NE1 7RU, UK
| | - Klaus Winter
- Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Ancón, Republic of Panama
| | - Anne M Borland
- School of Natural and Environmental Sciences, Newcastle University, Newcastle Upon Tyne, NE1 7RU, UK
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15
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Heyduk K, Ray JN, Leebens-Mack J. Leaf anatomy is not correlated to CAM function in a C3+CAM hybrid species, Yucca gloriosa. ANNALS OF BOTANY 2021; 127:437-449. [PMID: 32166326 PMCID: PMC7988526 DOI: 10.1093/aob/mcaa036] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2019] [Accepted: 03/05/2020] [Indexed: 05/22/2023]
Abstract
BACKGROUND AND AIMS Crassulacean acid metabolism (CAM) is often considered to be a complex trait, requiring orchestration of leaf anatomy and physiology for optimal performance. However, the observation of trait correlations is based largely on comparisons between C3 and strong CAM species, resulting in a lack of understanding as to how such traits evolve and the level of intraspecific variability for CAM and associated traits. METHODS To understand intraspecific variation for traits underlying CAM and how these traits might assemble over evolutionary time, we conducted detailed time course physiological screens and measured aspects of leaf anatomy in 24 genotypes of a C3+CAM hybrid species, Yucca gloriosa (Asparagaceae). Comparisons were made to Y. gloriosa's progenitor species, Y. filamentosa (C3) and Y. aloifolia (CAM). KEY RESULTS Based on gas exchange and measurement of leaf acids, Y. gloriosa appears to use both C3 and CAM, and varies across genotypes in the degree to which CAM can be upregulated under drought stress. While correlations between leaf anatomy and physiology exist when testing across all three Yucca species, such correlations break down at the species level in Y. gloriosa. CONCLUSIONS The variation in CAM upregulation in Y. gloriosa is a result of its relatively recent hybrid origin. The lack of trait correlations between anatomy and physiology within Y. gloriosa indicate that the evolution of CAM, at least initially, can proceed through a wide combination of anatomical traits, and more favourable combinations are eventually selected for in strong CAM plants.
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Affiliation(s)
- Karolina Heyduk
- School of Life Sciences, University of Hawai’i at Mānoa, Honolulu, HI, USA
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, USA
- For correspondence. E-mail
| | - Jeremy N Ray
- Department of Plant Biology, University of Georgia, Athens, GA, USA
| | - Jim Leebens-Mack
- Department of Plant Biology, University of Georgia, Athens, GA, USA
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16
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Ávila-Lovera E, Garcillán PP. Phylogenetic signal and climatic niche of stem photosynthesis in the mediterranean and desert regions of California and Baja California Peninsula. AMERICAN JOURNAL OF BOTANY 2021; 108:334-345. [PMID: 33280080 DOI: 10.1002/ajb2.1572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 08/26/2020] [Indexed: 06/12/2023]
Abstract
PREMISE Woody plants with photosynthetic stems are common in the drylands of the world; however, we know little about the origin(s) and geographical distribution of photosynthetic stems. Therefore, we set to answer the following questions: (1) Is stem photosynthesis phylogenetically conserved? (2) Do green-stemmed and fleshy-stemmed species have identifiable climatic niches? METHODS We mapped the photosynthetic stem trait onto a phylogeny of 228 mediterranean and desert species and calculated indices of phylogenetic signal and created climatic niche models of 28 species belonging to three groups: green, fleshy, and green-and-fleshy stemmed species. RESULTS We found phylogenetic signal in the fleshy stem trait, but not in the green stem trait. Fleshy-stemmed species occupy areas associated with high isothermality, high precipitation seasonality, and high mean temperature of the wettest quarter, whereas green-stemmed species occupy areas associated with high precipitation of driest month, high precipitation of coldest quarter, high mean diurnal temperature range and high maximum temperature of the warmest month. CONCLUSIONS Despite the fact that both photosynthetic stem types help cope with water shortage, having fleshy stems allows plants to cope with greater precipitation seasonality than is possible with green stems. Green stems require a lot of water to be stored in the soil to maintain net photosynthesis during the dry season, so they inhabit areas with higher and more predictable precipitation.
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Affiliation(s)
- Eleinis Ávila-Lovera
- Schimd College of Science and Technology, Chapman University. One University Drive, Orange, CA, 92866, USA
| | - Pedro P Garcillán
- Centro de Investigaciones Biológicas del Noroeste, Av. Instituto Politécnico Nacional 195, Col. Playa Palo de Santa Rita Sur, La Paz, B.C.S., 23096, México
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17
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Yuan G, Hassan MM, Liu D, Lim SD, Yim WC, Cushman JC, Markel K, Shih PM, Lu H, Weston DJ, Chen JG, Tschaplinski TJ, Tuskan GA, Yang X. Biosystems Design to Accelerate C 3-to-CAM Progression. BIODESIGN RESEARCH 2020; 2020:3686791. [PMID: 37849902 PMCID: PMC10521703 DOI: 10.34133/2020/3686791] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2020] [Accepted: 08/21/2020] [Indexed: 10/19/2023] Open
Abstract
Global demand for food and bioenergy production has increased rapidly, while the area of arable land has been declining for decades due to damage caused by erosion, pollution, sea level rise, urban development, soil salinization, and water scarcity driven by global climate change. In order to overcome this conflict, there is an urgent need to adapt conventional agriculture to water-limited and hotter conditions with plant crop systems that display higher water-use efficiency (WUE). Crassulacean acid metabolism (CAM) species have substantially higher WUE than species performing C3 or C4 photosynthesis. CAM plants are derived from C3 photosynthesis ancestors. However, it is extremely unlikely that the C3 or C4 crop plants would evolve rapidly into CAM photosynthesis without human intervention. Currently, there is growing interest in improving WUE through transferring CAM into C3 crops. However, engineering a major metabolic plant pathway, like CAM, is challenging and requires a comprehensive deep understanding of the enzymatic reactions and regulatory networks in both C3 and CAM photosynthesis, as well as overcoming physiometabolic limitations such as diurnal stomatal regulation. Recent advances in CAM evolutionary genomics research, genome editing, and synthetic biology have increased the likelihood of successful acceleration of C3-to-CAM progression. Here, we first summarize the systems biology-level understanding of the molecular processes in the CAM pathway. Then, we review the principles of CAM engineering in an evolutionary context. Lastly, we discuss the technical approaches to accelerate the C3-to-CAM transition in plants using synthetic biology toolboxes.
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Affiliation(s)
- Guoliang Yuan
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Md. Mahmudul Hassan
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
- Department of Genetics and Plant Breeding, Patuakhali Science and Technology University, Dumki, Patuakhali 8602, Bangladesh
| | - Degao Liu
- Department of Genetics, Cell Biology and Development, Center for Precision Plant Genomics, and Center for Genome Engineering, University of Minnesota, Saint Paul, MN 55108, USA
| | - Sung Don Lim
- Department of Applied Plant Sciences, Kangwon National University, Chuncheon 24341, Republic of Korea
| | - Won Cheol Yim
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV, USA
| | - John C. Cushman
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV, USA
| | - Kasey Markel
- Department of Plant Biology, University of California, Davis, Davis, CA, USA
| | - Patrick M. Shih
- Department of Plant Biology, University of California, Davis, Davis, CA, USA
- Feedstocks Division, Joint BioEnergy Institute, Emeryville, CA, USA
| | - Haiwei Lu
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - David J. Weston
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Jin-Gui Chen
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Timothy J. Tschaplinski
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Gerald A. Tuskan
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Xiaohan Yang
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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18
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Abraham PE, Hurtado Castano N, Cowan-Turner D, Barnes J, Poudel S, Hettich R, Flütsch S, Santelia D, Borland AM. Peeling back the layers of crassulacean acid metabolism: functional differentiation between Kalanchoë fedtschenkoi epidermis and mesophyll proteomes. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 103:869-888. [PMID: 32314451 DOI: 10.1111/tpj.14757] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Revised: 03/18/2020] [Accepted: 03/23/2020] [Indexed: 06/11/2023]
Abstract
Crassulacean acid metabolism (CAM) is a specialized mode of photosynthesis that offers the potential to engineer improved water-use efficiency (WUE) and drought resilience in C3 plants while sustaining productivity in the hotter and drier climates that are predicted for much of the world. CAM species show an inverted pattern of stomatal opening and closing across the diel cycle, which conserves water and provides a means of maintaining growth in hot, water-limited environments. Recent genome sequencing of the constitutive model CAM species Kalanchoë fedtschenkoi provides a platform for elucidating the ensemble of proteins that link photosynthetic metabolism with stomatal movement, and that protect CAM plants from harsh environmental conditions. We describe a large-scale proteomics analysis to characterize and compare proteins, as well as diel changes in their abundance in guard cell-enriched epidermis and mesophyll cells from leaves of K. fedtschenkoi. Proteins implicated in processes that encompass respiration, the transport of water and CO2 , stomatal regulation, and CAM biochemistry are highlighted and discussed. Diel rescheduling of guard cell starch turnover in K. fedtschenkoi compared with that observed in Arabidopsis is reported and tissue-specific localization in the epidermis and mesophyll of isozymes implicated in starch and malate turnover are discussed in line with the contrasting roles for these metabolites within the CAM mesophyll and stomatal complex. These data reveal the proteins and the biological processes enriched in each layer and provide key information for studies aiming to adapt plants to hot and dry environments by modifying leaf physiology for improved plant sustainability.
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Affiliation(s)
- Paul E Abraham
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Natalia Hurtado Castano
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, S10 2TN, UK
| | - Daniel Cowan-Turner
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
| | - Jeremy Barnes
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
| | - Suresh Poudel
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
- Department of Genome Science and Technology, University of Tennessee, Knoxville, TN, 37996, USA
| | - Robert Hettich
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | | | - Diana Santelia
- Institute of Integrative Biology, ETH, Zürich, Switzerland
| | - Anne M Borland
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
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19
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Herrera A. Are thick leaves, large mesophyll cells and small intercellular air spaces requisites for CAM? ANNALS OF BOTANY 2020; 125:859-868. [PMID: 31970387 PMCID: PMC7218806 DOI: 10.1093/aob/mcaa008] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Accepted: 01/21/2020] [Indexed: 05/13/2023]
Abstract
BACKGROUND AND AIMS It is commonly accepted that the leaf of a crassulacean acid metabolism (CAM) plant is thick, with large mesophyll cells and vacuoles that can accommodate the malic acid produced during the night. The link between mesophyll characteristics and CAM mode, whether obligate or C3/CAM, was evaluated. METHODS Published values of the carbon isotopic ratio (δ 13C) as an indicator of CAM, leaf thickness, leaf micrographs and other evidence of CAM operation were used to correlate cell density, cell area, the proportion of intercellular space in the mesophyll (IAS) and the length of cell wall facing the intercellular air spaces (Lmes/A) with CAM mode. KEY RESULTS Based on 81 species and relatively unrelated families (15) belonging to nine orders, neither leaf thickness nor mesophyll traits helped explain the degree of CAM expression. A strong correlation was found between leaf thickness and δ 13C in some species of Crassulaceae and between leaf thickness and nocturnal acid accumulation in a few obligate CAM species of Bromeliaceae but, when all 81 species were pooled together, no significant changes with δ 13C were observed in cell density, cell area, IAS or Lmes/A. CONCLUSIONS An influence of phylogeny on leaf anatomy was evidenced in a few cases but this precluded generalization for widely separate taxa containing CAM species. The possible relationships between leaf anatomy and CAM mode should be interpreted cautiously.
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Affiliation(s)
- Ana Herrera
- Centro de Botánica Tropical, Instituto de Biología Experimental, Universidad Central de Venezuela, Caracas, Venezuela
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20
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Chomthong M, Griffiths H. Model approaches to advance crassulacean acid metabolism system integration. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 101:951-963. [PMID: 31943394 DOI: 10.1111/tpj.14691] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Accepted: 01/02/2020] [Indexed: 06/10/2023]
Abstract
This review summarises recent progress in understanding crassulacean acid metabolism (CAM) systems and the integration of internal and external stimuli to maximise water-use efficiency. Complex CAM traits have been reduced to their minimum and captured as computational models, which can now be refined using recently available data from transgenic manipulations and large-scale omics studies. We identify three key areas in which an appropriate choice of modelling tool could help capture relevant comparative molecular data to address the evolutionary drivers and plasticity of CAM. One focus is to identify the environmental and internal signals that drive inverse stomatal opening at night. Secondly, it is important to identify the regulatory processes required to orchestrate the diel pattern of carbon fluxes within mesophyll layers. Finally, the limitations imposed by contrasting succulent systems and associated hydraulic conductance components should be compared in the context of water-use and evolutionary strategies. While network analysis of transcriptomic data can provide insights via co-expression modules and hubs, alternative forms of computational modelling should be used iteratively to define the physiological significance of key components and informing targeted functional gene manipulation studies. We conclude that the resultant improvements of bottom-up, mechanistic modelling systems can enhance progress towards capturing the physiological controls for phylogenetically diverse CAM systems in the face of the recent surge of information in this omics era.
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Affiliation(s)
- Methawi Chomthong
- Department of Plant Sciences, University of Cambridge, Downing street, Cambridge, CB2 3EA, UK
| | - Howard Griffiths
- Department of Plant Sciences, University of Cambridge, Downing street, Cambridge, CB2 3EA, UK
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21
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Liu D, Chen M, Mendoza B, Cheng H, Hu R, Li L, Trinh CT, Tuskan GA, Yang X. CRISPR/Cas9-mediated targeted mutagenesis for functional genomics research of crassulacean acid metabolism plants. JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:6621-6629. [PMID: 31562521 PMCID: PMC6883263 DOI: 10.1093/jxb/erz415] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Accepted: 08/29/2019] [Indexed: 05/17/2023]
Abstract
Crassulacean acid metabolism (CAM) is an important photosynthetic pathway in diverse lineages of plants featuring high water-use efficiency and drought tolerance. A big challenge facing the CAM research community is to understand the function of the annotated genes in CAM plant genomes. Recently, a new genome editing technology using CRISPR/Cas9 has become a more precise and powerful tool than traditional approaches for functional genomics research in C3 and C4 plants. In this study, we explore the potential of CRISPR/Cas9 to characterize the function of CAM-related genes in the model CAM species Kalanchoë fedtschenkoi. We demonstrate that CRISPR/Cas9 is effective in creating biallelic indel mutagenesis to reveal previously unknown roles of blue light receptor phototropin 2 (KfePHOT2) in the CAM pathway. Knocking out KfePHOT2 reduced stomatal conductance and CO2 fixation in late afternoon and increased stomatal conductance and CO2 fixation during the night, indicating that blue light signaling plays an important role in the CAM pathway. Lastly, we provide a genome-wide guide RNA database targeting 45 183 protein-coding transcripts annotated in the K. fedtschenkoi genome.
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Affiliation(s)
- Degao Liu
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
- DOE-Center for Bioenergy Innovation (CBI), Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Mei Chen
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
- School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang, Sichuan, China
| | - Brian Mendoza
- Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, TN, USA
| | - Hua Cheng
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Rongbin Hu
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Linling Li
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Cong T Trinh
- DOE-Center for Bioenergy Innovation (CBI), Oak Ridge National Laboratory, Oak Ridge, TN, USA
- Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, TN, USA
| | - Gerald A Tuskan
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
- DOE-Center for Bioenergy Innovation (CBI), Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Xiaohan Yang
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
- DOE-Center for Bioenergy Innovation (CBI), Oak Ridge National Laboratory, Oak Ridge, TN, USA
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22
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Edwards EJ. Evolutionary trajectories, accessibility and other metaphors: the case of C 4 and CAM photosynthesis. THE NEW PHYTOLOGIST 2019; 223:1742-1755. [PMID: 30993711 DOI: 10.1111/nph.15851] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Accepted: 03/18/2019] [Indexed: 05/24/2023]
Abstract
Are evolutionary outcomes predictable? Adaptations that show repeated evolutionary convergence across the Tree of Life provide a special opportunity to dissect the context surrounding their origins, and identify any commonalities that may predict why certain traits evolved many times in particular clades and yet never evolved in others. The remarkable convergence of C4 and Crassulacean Acid Metabolism (CAM) photosynthesis in vascular plants makes them exceptional model systems for understanding the repeated evolution of complex phenotypes. This review highlights what we have learned about the recurring assembly of C4 and CAM, focusing on the increasingly predictable stepwise evolutionary integration of anatomy and biochemistry. With the caveat that we currently understand C4 evolution better than we do CAM, I propose a general model that explains and unites C4 and CAM evolutionary trajectories. Available data suggest that anatomical modifications are the 'rate-limiting step' in each trajectory, which in large part determines the evolutionary accessibility of both syndromes. The idea that organismal structure exerts a primary influence on innovation is discussed in the context of other systems. Whether the rate-limiting step occurs early or late in the evolutionary assembly of a new phenotype may have profound implications for its distribution across the Tree of Life.
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Affiliation(s)
- Erika J Edwards
- Department of Ecology and Evolutionary Biology, Yale University, 165 Prospect St, New Haven, CT, 06520-8105, USA
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