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Altamura MM, Piacentini D, Della Rovere F, Fattorini L, Valletta A, Falasca G. Plastid dynamism integrates development and environment. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2024; 213:108813. [PMID: 38861821 DOI: 10.1016/j.plaphy.2024.108813] [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: 04/26/2024] [Revised: 06/06/2024] [Accepted: 06/07/2024] [Indexed: 06/13/2024]
Abstract
In land plants plastid type differentiation occurs concomitantly with cellular differentiation and the transition from one type to another is under developmental and environmental control. Plastid dynamism is based on a bilateral communication between plastids and nucleus through anterograde and retrograde signaling. Signaling occurs through the interaction with specific phytohormones (abscisic acid, strigolactones, jasmonates, gibberellins, brassinosteroids, ethylene, salicylic acid, cytokinin and auxin). The review is focused on the modulation of plastid capabilities at both transcriptional and post-translational levels at the crossroad between development and stress, with a particular attention to the chloroplast, because the most studied plastid type. The role of plastid-encoded and nuclear-encoded proteins for plastid development and stress responses, and the changes of plastid fate through the activity of stromules and plastoglobules, are discussed. Examples of plastid dynamism in response to soil stress agents (salinity, lead, cadmium, arsenic, and chromium) are described. Albinism and root greening are described based on the modulation activities of auxin and cytokinin. The physiological and functional responses of the sensory epidermal and vascular plastids to abiotic and biotic stresses along with their specific roles in stress sensing are described together with their potential modulation of retrograde signaling pathways. Future research perspectives include an in-depth study of sensory plastids to explore their potential for establishing a transgenerational memory to stress. Suggestions about anterograde and retrograde pathways acting at interspecific level and on the lipids of plastoglobules as a novel class of plastid morphogenic agents are provided.
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Affiliation(s)
| | - Diego Piacentini
- Department of Environmental Biology, Sapienza University of Rome, Italy
| | | | - Laura Fattorini
- Department of Environmental Biology, Sapienza University of Rome, Italy
| | - Alessio Valletta
- Department of Environmental Biology, Sapienza University of Rome, Italy
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2
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Wan C, Zhang H, Cheng H, Sowden RG, Cai W, Jarvis RP, Ling Q. Selective autophagy regulates chloroplast protein import and promotes plant stress tolerance. EMBO J 2023; 42:e112534. [PMID: 37248861 PMCID: PMC10350842 DOI: 10.15252/embj.2022112534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 03/26/2023] [Accepted: 05/09/2023] [Indexed: 05/31/2023] Open
Abstract
Chloroplasts are plant organelles responsible for photosynthesis and environmental sensing. Most chloroplast proteins are imported from the cytosol through the translocon at the outer envelope membrane of chloroplasts (TOC). Previous work has shown that TOC components are regulated by the ubiquitin-proteasome system (UPS) to control the chloroplast proteome, which is crucial for the organelle's function and plant development. Here, we demonstrate that the TOC apparatus is also subject to K63-linked polyubiquitination and regulation by selective autophagy, potentially promoting plant stress tolerance. We identify NBR1 as a selective autophagy adaptor targeting TOC components, and mediating their relocation into vacuoles for autophagic degradation. Such selective autophagy is shown to control TOC protein levels and chloroplast protein import and to influence photosynthetic activity as well as tolerance to UV-B irradiation and heat stress in Arabidopsis plants. These findings uncover the vital role of selective autophagy in the proteolytic regulation of specific chloroplast proteins, and how dynamic control of chloroplast protein import is critically important for plants to cope with challenging environments.
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Affiliation(s)
- Chen Wan
- National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and EcologyChinese Academy of SciencesShanghaiChina
- University of Chinese Academy of SciencesBeijingChina
| | - Hui Zhang
- National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and EcologyChinese Academy of SciencesShanghaiChina
| | - Hongying Cheng
- National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and EcologyChinese Academy of SciencesShanghaiChina
- University of Chinese Academy of SciencesBeijingChina
| | - Robert G Sowden
- Department of Plant Sciences and Section of Molecular Plant Biology (Department of Biology)University of OxfordOxfordUK
| | - Wenjuan Cai
- Core Facility Center, CAS Centre for Excellence in Molecular Plant SciencesChinese Academy of SciencesShanghaiChina
| | - R Paul Jarvis
- Department of Plant Sciences and Section of Molecular Plant Biology (Department of Biology)University of OxfordOxfordUK
| | - Qihua Ling
- National Key Laboratory of Plant Molecular Genetics, CAS Centre for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and EcologyChinese Academy of SciencesShanghaiChina
- University of Chinese Academy of SciencesBeijingChina
- CAS‐JIC Center of Excellence for Plant and Microbial Sciences (CEPAMS), Institute of Plant Physiology and EcologyChinese Academy of SciencesShanghaiChina
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Yoshitake Y, Yoshimoto K. Intracellular phosphate recycling systems for survival during phosphate starvation in plants. FRONTIERS IN PLANT SCIENCE 2023; 13:1088211. [PMID: 36733584 PMCID: PMC9888252 DOI: 10.3389/fpls.2022.1088211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Accepted: 12/23/2022] [Indexed: 06/18/2023]
Abstract
Phosphorus (P) is an essential nutrient for plant growth and plants use inorganic phosphate (Pi) as their P source, but its bioavailable form, orthophosphate, is often limited in soils. Hence, plants have several mechanisms for adaptation to Pi starvation. One of the most common response strategies is "Pi recycling" in which catabolic enzymes degrade intracellular constituents, such as phosphoesters, nucleic acids and glycerophospholipids to salvage Pi. Recently, several other intracellular degradation systems have been discovered that salvage Pi from organelles. Also, one of sphingolipids has recently been identified as a degradation target for Pi recycling. So, in this mini-review we summarize the current state of knowledge, including research findings, about the targets and degradation processes for Pi recycling under Pi starvation, in order to further our knowledge of the whole mechanism of Pi recycling.
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4
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Pexophagy suppresses ROS-induced damage in leaf cells under high-intensity light. Nat Commun 2022; 13:7493. [PMID: 36470866 PMCID: PMC9722907 DOI: 10.1038/s41467-022-35138-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Accepted: 11/18/2022] [Indexed: 12/12/2022] Open
Abstract
Although light is essential for photosynthesis, it has the potential to elevate intracellular levels of reactive oxygen species (ROS). Since high ROS levels are cytotoxic, plants must alleviate such damage. However, the cellular mechanism underlying ROS-induced leaf damage alleviation in peroxisomes was not fully explored. Here, we show that autophagy plays a pivotal role in the selective removal of ROS-generating peroxisomes, which protects plants from oxidative damage during photosynthesis. We present evidence that autophagy-deficient mutants show light intensity-dependent leaf damage and excess aggregation of ROS-accumulating peroxisomes. The peroxisome aggregates are specifically engulfed by pre-autophagosomal structures and vacuolar membranes in both leaf cells and isolated vacuoles, but they are not degraded in mutants. ATG18a-GFP and GFP-2×FYVE, which bind to phosphatidylinositol 3-phosphate, preferentially target the peroxisomal membranes and pre-autophagosomal structures near peroxisomes in ROS-accumulating cells under high-intensity light. Our findings provide deeper insights into the plant stress response caused by light irradiation.
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Rowland E, Kim J, Friso G, Poliakov A, Ponnala L, Sun Q, van Wijk KJ. The CLP and PREP protease systems coordinate maturation and degradation of the chloroplast proteome in Arabidopsis thaliana. THE NEW PHYTOLOGIST 2022; 236:1339-1357. [PMID: 35946374 DOI: 10.1111/nph.18426] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 07/29/2022] [Indexed: 06/15/2023]
Abstract
A network of peptidases governs proteostasis in plant chloroplasts and mitochondria. This study reveals strong genetic and functional interactions in Arabidopsis between the chloroplast stromal CLP chaperone-protease system and the PREP1,2 peptidases, which are dually localized to chloroplast stroma and the mitochondrial matrix. Higher order mutants defective in CLP or PREP proteins were generated and analyzed by quantitative proteomics and N-terminal proteomics (terminal amine isotopic labeling of substrates (TAILS)). Strong synergistic interactions were observed between the CLP protease system (clpr1-2, clpr2-1, clpc1-1, clpt1, clpt2) and both PREP homologs (prep1, prep2) resulting in embryo lethality or growth and developmental phenotypes. Synergistic interactions were observed even when only one of the PREP proteins was lacking, suggesting that PREP1 and PREP2 have divergent substrates. Proteome phenotypes were driven by the loss of CLP protease capacity, with little impact from the PREP peptidases. Chloroplast N-terminal proteomes showed that many nuclear encoded chloroplast proteins have alternatively processed N-termini in prep1prep2, clpt1clpt2 and prep1prep2clpt1clpt2. Loss of chloroplast protease capacity interferes with stromal processing peptidase (SPP) activity due to folding stress and low levels of accumulated cleaved cTP fragments. PREP1,2 proteolysis of cleaved cTPs is complemented by unknown proteases. A model for CLP and PREP activity within a hierarchical chloroplast proteolysis network is proposed.
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Affiliation(s)
- Elden Rowland
- Section of Plant Biology, School of Integrative Plant Sciences (SIPS), Cornell University, Ithaca, NY, 14853, USA
| | - Jitae Kim
- Section of Plant Biology, School of Integrative Plant Sciences (SIPS), Cornell University, Ithaca, NY, 14853, USA
- S-Korea Bioenergy Research Center, Chonnam National University, Gwangju, 61186, South Korea
| | - Giulia Friso
- Section of Plant Biology, School of Integrative Plant Sciences (SIPS), Cornell University, Ithaca, NY, 14853, USA
| | - Anton Poliakov
- Section of Plant Biology, School of Integrative Plant Sciences (SIPS), Cornell University, Ithaca, NY, 14853, USA
| | | | - Qi Sun
- Computational Biology Service Unit, Cornell University, Ithaca, NY, 14853, USA
| | - Klaas J van Wijk
- Section of Plant Biology, School of Integrative Plant Sciences (SIPS), Cornell University, Ithaca, NY, 14853, USA
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Sharma I, Kirti PB, Pati PK. Autophagy: a game changer for plant development and crop improvement. PLANTA 2022; 256:103. [PMID: 36307739 DOI: 10.1007/s00425-022-04004-z] [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: 05/19/2022] [Accepted: 09/21/2022] [Indexed: 06/16/2023]
Abstract
Manipulation of autophagic pathway represents a tremendous opportunity for designing climate-smart crops with improved yield and better adaptability to changing environment. For exploiting autophagy to its full potential, identification and comprehensive characterization of adapters/receptor complex and elucidation of its regulatory network in crop plants is highly warranted. Autophagy is a major intracellular trafficking pathway in eukaryotes involved in vacuolar degradation of cytoplasmic constituents, mis-folded proteins, and defective organelles. Under optimum conditions, autophagy operates at a basal level to maintain cellular homeostasis, but under stressed conditions, it is induced further to provide temporal stress relief. Our understanding of this highly dynamic process has evolved exponentially in the past few years with special reference to several plant-specific roles of autophagy. Here, we review the most recent advances in the field of autophagy in plants and discuss its potential implications in designing crops with improved stress and disease-tolerance, enhanced yield potential, and improved capabilities for producing metabolites of high economic value. We also assess the current knowledge gaps and the possible strategies to develop a robust module for biotechnological application of autophagy to enhance bioeconomy and sustainability of agriculture.
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Affiliation(s)
- Isha Sharma
- AgriBiotech Foundation, PJTS Agriculture University, Rajendranagar, Hyderabad, Telangana, 500032, India.
- International Crops Research Institute for the Semi-Arid Tropics, 502324, Patancheru, Telangana, India.
| | | | - Pratap Kumar Pati
- Department of Biotechnology, Guru Nanak Dev University, Amritsar, Punjab, 140301, India
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Lee HY, Hwang OJ, Back K. Phytomelatonin as a signaling molecule for protein quality control via chaperone, autophagy, and ubiquitin-proteasome systems in plants. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:5863-5873. [PMID: 35246975 DOI: 10.1093/jxb/erac002] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Accepted: 03/04/2022] [Indexed: 06/14/2023]
Abstract
Physiological effects mediated by melatonin are attributable to its potent antioxidant activity as well as its role as a signaling molecule in inducing a vast array of melatonin-mediated genes. Here, we propose melatonin as a signaling molecule essential for protein quality control (PQC) in plants. PQC occurs by the coordinated activities of three systems: the chaperone network, autophagy, and the ubiquitin-proteasome system. With regard to the melatonin-mediated chaperone pathway, melatonin increases thermotolerance by induction of heat shock proteins and confers endoplasmic reticulum stress tolerance by increasing endoplasmic reticulum chaperone proteins. In chloroplasts, melatonin-induced chaperones, including Clps and CpHSP70s, play key roles in the PQC of chloroplast-localized proteins, such as Lhcb1, Lhcb4, and RBCL, during growth. Melatonin regulates PQC by autophagy processes, in which melatonin induces many autophagy (ATG) genes and autophagosome formation under stress conditions. Finally, melatonin-mediated plant stress tolerance is associated with up-regulation of stress-induced transcription factors, which are regulated by the ubiquitin-proteasome system. In this review, we propose that melatonin plays a pivotal role in PQC and consequently functions as a pleiotropic molecule under non-stress and adverse conditions in plants.
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Affiliation(s)
- Hyoung Yool Lee
- Department of Biotechnology, College of Agriculture and Life Sciences, Chonnam National University, Gwangju 61186, South Korea
| | - Ok Jin Hwang
- Department of Biotechnology, College of Agriculture and Life Sciences, Chonnam National University, Gwangju 61186, South Korea
| | - Kyoungwhan Back
- Department of Biotechnology, College of Agriculture and Life Sciences, Chonnam National University, Gwangju 61186, South Korea
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8
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Sakuraba Y. Molecular basis of nitrogen starvation-induced leaf senescence. FRONTIERS IN PLANT SCIENCE 2022; 13:1013304. [PMID: 36212285 PMCID: PMC9538721 DOI: 10.3389/fpls.2022.1013304] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2022] [Accepted: 09/08/2022] [Indexed: 06/01/2023]
Abstract
Nitrogen (N), a macronutrient, is often a limiting factor in plant growth, development, and productivity. To adapt to N-deficient environments, plants have developed elaborate N starvation responses. Under N-deficient conditions, older leaves exhibit yellowing, owing to the degradation of proteins and chlorophyll pigments in chloroplasts and subsequent N remobilization from older leaves to younger leaves and developing organs to sustain plant growth and productivity. In recent years, numerous studies have been conducted on N starvation-induced leaf senescence as one of the representative plant responses to N deficiency, revealing that leaf senescence induced by N deficiency is highly complex and intricately regulated at different levels, including transcriptional, post-transcriptional, post-translational and metabolic levels, by multiple genes and proteins. This review summarizes the current knowledge of the molecular mechanisms associated with N starvation-induced leaf senescence.
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9
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Behr M, Speeckaert N, Kurze E, Morel O, Prévost M, Mol A, Mahamadou Adamou N, Baragé M, Renaut J, Schwab W, El Jaziri M, Baucher M. Leaf necrosis resulting from downregulation of poplar glycosyltransferase UGT72A2. TREE PHYSIOLOGY 2022; 42:1084-1099. [PMID: 34865151 DOI: 10.1093/treephys/tpab161] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 11/29/2021] [Indexed: 06/13/2023]
Abstract
Reactive species (RS) causing oxidative stress are unavoidable by-products of various plant metabolic processes, such as photosynthesis, respiration or photorespiration. In leaves, flavonoids scavenge RS produced during photosynthesis and protect plant cells against deleterious oxidative damages. Their biosynthesis and accumulation are therefore under tight regulation at the cellular level. Glycosylation has emerged as an essential biochemical reaction in the homeostasis of various specialized metabolites such as flavonoids. This article provides a functional characterization of the Populus tremula x P. alba (poplar) UGT72A2 coding for a UDP-glycosyltransferase that is localized in the chloroplasts. Compared with the wild type, transgenic poplar lines with decreased expression of UGT72A2 are characterized by reduced growth and oxidative damages in leaves, as evidenced by necrosis, higher content of glutathione and lipid peroxidation products as well as diminished soluble peroxidase activity and NADPH to NADP+ ratio under standard growing conditions. They furthermore display lower pools of phenolics, anthocyanins and total flavonoids but higher proanthocyanidins content. Promoter analysis revealed the presence of cis-elements involved in photomorphogenesis, chloroplast biogenesis and flavonoid biosynthesis. The UGT72A2 is regulated by the poplar MYB119, a transcription factor known to regulate the flavonoid biosynthesis pathway. Phylogenetic analysis and molecular docking suggest that UGT72A2 could glycosylate flavonoids; however, the actual substrate(s) was not consistently evidenced with either in vitro assays nor analyses of glycosylated products in leaves of transgenic poplar overexpressing or downregulated for UGT72A2. This article provides elements highlighting the importance of flavonoid glycosylation regarding protection against oxidative stress in poplar leaves and raises new questions about the link between this biochemical reaction and regulation of the redox homeostasis system.
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Affiliation(s)
- Marc Behr
- Laboratory of Plant Biotechnology, Université libre de Bruxelles, 12 rue des Profs Jeener et Brachet, Gosselies 6041, Belgium
| | - Nathanael Speeckaert
- Laboratory of Plant Biotechnology, Université libre de Bruxelles, 12 rue des Profs Jeener et Brachet, Gosselies 6041, Belgium
| | - Elisabeth Kurze
- Biotechnology of Natural Products, Technische Universität München, 85354 Freising, Germany
| | - Oriane Morel
- Laboratory of Plant Biotechnology, Université libre de Bruxelles, 12 rue des Profs Jeener et Brachet, Gosselies 6041, Belgium
| | - Martine Prévost
- Unité de recherche Structure et Fonction des Membranes Biologiques, Université libre de Bruxelles, Bruxelles, Belgium
| | - Adeline Mol
- Laboratory of Plant Biotechnology, Université libre de Bruxelles, 12 rue des Profs Jeener et Brachet, Gosselies 6041, Belgium
| | - Nassirou Mahamadou Adamou
- Laboratory of Plant Biotechnology, Université libre de Bruxelles, 12 rue des Profs Jeener et Brachet, Gosselies 6041, Belgium
- Laboratoire de Biotechnologie Végétale et Amélioration des Plantes (LABAP), Université Abdou Moumouni de Niamey, Niamey, Niger
| | - Moussa Baragé
- Laboratoire de Biotechnologie Végétale et Amélioration des Plantes (LABAP), Université Abdou Moumouni de Niamey, Niamey, Niger
| | - Jenny Renaut
- Luxembourg Institute of Science and Technology, 4422 Belvaux, Luxembourg
| | - Wilfried Schwab
- Biotechnology of Natural Products, Technische Universität München, 85354 Freising, Germany
| | - Mondher El Jaziri
- Laboratory of Plant Biotechnology, Université libre de Bruxelles, 12 rue des Profs Jeener et Brachet, Gosselies 6041, Belgium
| | - Marie Baucher
- Laboratory of Plant Biotechnology, Université libre de Bruxelles, 12 rue des Profs Jeener et Brachet, Gosselies 6041, Belgium
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10
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Woodson JD. Control of chloroplast degradation and cell death in response to stress. Trends Biochem Sci 2022; 47:851-864. [DOI: 10.1016/j.tibs.2022.03.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 02/25/2022] [Accepted: 03/14/2022] [Indexed: 12/16/2022]
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11
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Fisher KE, Krishnamoorthy P, Joens MS, Chory J, Fitzpatrick JAJ, Woodson JD. Singlet Oxygen Leads to Structural Changes to Chloroplasts during their Degradation in the Arabidopsis thaliana plastid ferrochelatase two Mutant. PLANT & CELL PHYSIOLOGY 2022; 63:248-264. [PMID: 34850209 DOI: 10.1093/pcp/pcab167] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 11/01/2021] [Accepted: 11/22/2021] [Indexed: 06/13/2023]
Abstract
During stress, chloroplasts produce large amounts of reactive oxygen species (ROS). Chloroplasts also contain many nutrients, including 80% of a leaf's nitrogen supply. Therefore, to protect cells from photo-oxidative damage and to redistribute nutrients to sink tissues, chloroplasts are prime targets for degradation. Multiple chloroplast degradation pathways are induced by photo-oxidative stress or nutrient starvation, but the mechanisms by which damaged or senescing chloroplasts are identified, transported to the central vacuole and degraded are poorly defined. Here, we investigated the structures involved with degrading chloroplasts induced by the ROS singlet oxygen (1O2) in the Arabidopsis thaliana plastid ferrochelatase two (fc2) mutant. Under mild 1O2 stress, most fc2 chloroplasts appeared normal, but had reduced starch content. A subset of chloroplasts was degrading, and some protruded into the central vacuole via 'blebbing' structures. A 3D electron microscopy analysis demonstrated that up to 35% of degrading chloroplasts contained such structures. While the location of a chloroplast within a cell did not affect the likelihood of its degradation, chloroplasts in spongy mesophyll cells were degraded at a higher rate than those in palisade mesophyll cells. To determine if degrading chloroplasts have unique structural characteristics, allowing them to be distinguished from healthy chloroplasts, we analyzed fc2 seedlings grown under different levels of photo-oxidative stress. A correlation was observed among chloroplast swelling, 1O2 signaling and the state of degradation. Finally, plastoglobule (PG) enzymes involved in chloroplast disassembly were upregulated while PGs increased their association with the thylakoid grana, implicating an interaction between 1O2-induced chloroplast degradation and senescence pathways.
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Affiliation(s)
- Karen E Fisher
- The School of Plant Sciences, University of Arizona, 1140 E South Campus Dr., Tucson, AZ 85721, USA
| | - Praveen Krishnamoorthy
- Washington University Center for Cellular Imaging, Washington University School of Medicine, 660 W. Euclid Avenue, St. Louis, MO 63110, USA
| | | | - Joanne Chory
- Plant Biology Laboratory and the Howard Hughes Medical Institute, The Salk Institute, 10010 N Torrey Pines Rd., La Jolla, CA 92037, USA
| | - James A J Fitzpatrick
- Washington University Center for Cellular Imaging, Washington University School of Medicine, 660 W. Euclid Avenue, St. Louis, MO 63110, USA
- Departments of Cell Biology & Physiology and Neuroscience, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA
- Department of Biomedical Engineering, Washington University in St. Louis, 1 Brookings Drive, St. Louis, MO 63130, USA
| | - Jesse D Woodson
- The School of Plant Sciences, University of Arizona, 1140 E South Campus Dr., Tucson, AZ 85721, USA
- Washington University Center for Cellular Imaging, Washington University School of Medicine, 660 W. Euclid Avenue, St. Louis, MO 63110, USA
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Samal B, Chatterjee S. Bacterial quorum sensing facilitates Xanthomonas campesteris pv. campestris invasion of host tissue to maximize disease symptoms. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:6524-6543. [PMID: 33993246 DOI: 10.1093/jxb/erab211] [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: 11/03/2020] [Accepted: 05/12/2021] [Indexed: 06/12/2023]
Abstract
Quorum sensing (QS) helps the Xanthomonas group of phytopathogens to infect several crop plants. The vascular phytopathogen Xanthomonas campestris pv. campestris (Xcc) is the causal agent of black rot disease on Brassicaceae leaves, where a typical v-shaped lesion spans both vascular and mesophyll regions with progressive leaf chlorosis. Recently, the role of QS has been elucidated during Xcc early infection stages. However, a detailed insight into the possible role of QS-regulated bacterial invasion in host chlorophagy during late infection stages remains elusive. In this study, using QS-responsive whole-cell bioreporters of Xcc, we present a detailed chronology of QS-facilitated Xcc colonization in the mesophyll region of cabbage (Brassica oleracea) leaves. We report that QS-enabled localization of Xcc to parenchymal chloroplasts triggers leaf chlorosis and promotion of systemic infection. Our results indicate that the QS response in the Xanthomonas group of vascular phytopathogens maximizes their population fitness across host tissues to trigger stage-specific host chlorophagy and establish a systemic infection.
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Affiliation(s)
- Biswajit Samal
- Lab of Plant-Microbe Interactions, Centre for DNA Fingerprinting and Diagnostics, Hyderabad, Telangana, India
- Graduate Studies, Manipal Academy of Higher Education, Manipal, Karnataka, India
| | - Subhadeep Chatterjee
- Lab of Plant-Microbe Interactions, Centre for DNA Fingerprinting and Diagnostics, Hyderabad, Telangana, India
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13
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Gao T, Liu Y, Liu X, Zhao K, Shan L, Wu Q, Liu Y, Zhang Z, Ma F, Li C. Exogenous dopamine and overexpression of the dopamine synthase gene MdTYDC alleviated apple replant disease. TREE PHYSIOLOGY 2021; 41:1524-1541. [PMID: 33171491 DOI: 10.1093/treephys/tpaa154] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 11/08/2020] [Indexed: 05/25/2023]
Abstract
Apple replant disease (ARD) is a soil-borne disease that leads to economic losses due to reduced plant growth and diminished fruit yields. Dopamine is involved in interactions between plants and pathogens. However, it remains unclear whether dopamine can directly stimulate defense responses to ARD. In this study, an exogenous dopamine treatment and dopamine synthetase MdTYDC (tyrosine decarboxylase) transgenic plants were used to verify the role of dopamine in treating ARD. First, 2-year-old apple trees (Malus domestica cv. Fuji), grafted onto rootstock M26, were grown in replant soils. The addition of dopamine (100 μM) to the soil promoted seedling growth and changed the accumulation of mineral elements in plants in replant soils. Such supplementation improved the activity of invertase, urease, proteinase and phosphatase under replant conditions. Sequencing analysis of 16S rDNA and internal transcribed spacer (ITS) rDNA revealed that dopamine had a slight influence on bacterial diversity but had an obvious effect on the fungal diversity in replant soils. The application of dopamine to replant soil changed the composition of bacterial and fungal communities. Second, overexpression of MdTYDC in apple plants alleviated the effects of ARD. MdTYDC transgenic lines exhibited mitigated ARD through inhibited degradation of photosynthetic pigment, maintaining the stability of photosystems I and II and improving the antioxidant system. Furthermore, overexpression of MdTYDC improved arbuscular mycorrhizal fungi colonization by improving the accumulation of soluble sugars under replant conditions. Together, these results demonstrated that dopamine enhances the tolerance of apples to ARD.
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Affiliation(s)
- Tengteng Gao
- State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Yusong Liu
- State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Xiaomin Liu
- State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Kai Zhao
- State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Lei Shan
- State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Qian Wu
- State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Yuan Liu
- State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Zhijun Zhang
- State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Fengwang Ma
- State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Chao Li
- State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China
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14
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Ma L, Li G. Arabidopsis FAR-RED ELONGATED HYPOCOTYL3 negatively regulates carbon starvation responses. PLANT, CELL & ENVIRONMENT 2021; 44:1816-1829. [PMID: 33715163 DOI: 10.1111/pce.14044] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 03/01/2021] [Accepted: 03/06/2021] [Indexed: 06/12/2023]
Abstract
Light is one of the most important environmental factors that affects various cellular processes in plant growth and development; it is also crucial for the metabolism of carbohydrates as it provides the energy source for photosynthesis. Under extended darkness conditions, carbon starvation responses are triggered by depletion of stored energy. Although light rapidly inhibits starvation responses, the molecular mechanisms by which light signalling affects this process remain largely unknown. In this study, we showed that the Arabidopsis thaliana light signalling protein FAR-RED ELONGATED HYPOCOTYL3 (FHY3) and its homolog FAR-RED IMPAIRED RESPONSE1 (FAR1) are essential for plant survival after extended darkness treatment at both seedling and adult stages. Transmission electron microscopy analyses revealed that disruption of both FHY3 and FAR1 resulted in destruction of chloroplast envelopes and thylakoid membranes under extended darkness conditions. Furthermore, treatment with sucrose, but not glucose, completely rescued carbon starvation-induced cell death in the rosette leaves and arrested early seedling establishment in the fhy3 far1 plants. We thus concluded that the light signalling proteins FHY3 and FAR1 negatively regulate carbon starvation responses in Arabidopsis.
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Affiliation(s)
- Lin Ma
- School of Biological Science and Technology, University of Jinan, Jinan, China
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an, China
| | - Gang Li
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an, China
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15
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EMS Derived Wheat Mutant BIG8-1 ( Triticum aestivum L.)-A New Drought Tolerant Mutant Wheat Line. Int J Mol Sci 2021; 22:ijms22105314. [PMID: 34070033 PMCID: PMC8158095 DOI: 10.3390/ijms22105314] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Revised: 04/22/2021] [Accepted: 04/29/2021] [Indexed: 12/20/2022] Open
Abstract
Drought response in wheat is considered a highly complex process, since it is a multigenic trait; nevertheless, breeding programs are continuously searching for new wheat varieties with characteristics for drought tolerance. In a previous study, we demonstrated the effectiveness of a mutant known as RYNO3936 that could survive 14 days without water. In this study, we reveal another mutant known as BIG8-1 that can endure severe water deficit stress (21 days without water) with superior drought response characteristics. Phenotypically, the mutant plants had broader leaves, including a densely packed fibrous root architecture that was not visible in the WT parent plants. During mild (day 7) drought stress, the mutant could maintain its relative water content, chlorophyll content, maximum quantum yield of PSII (Fv/Fm) and stomatal conductance, with no phenotypic symptoms such as wilting or senescence despite a decrease in soil moisture content. It was only during moderate (day 14) and severe (day 21) water deficit stress that a decline in those variables was evident. Furthermore, the mutant plants also displayed a unique preservation of metabolic activity, which was confirmed by assessing the accumulation of free amino acids and increase of antioxidative enzymes (peroxidases and glutathione S-transferase). Proteome reshuffling was also observed, allowing slow degradation of essential proteins such as RuBisCO during water deficit stress. The LC-MS/MS data revealed a high abundance of proteins involved in energy and photosynthesis under well-watered conditions, particularly Serpin-Z2A and Z2B, SGT1 and Calnexin-like protein. However, after 21 days of water stress, the mutants expressed ABC transporter permeases and xylanase inhibitor protein, which are involved in the transport of amino acids and protecting cells, respectively. This study characterizes a new mutant BIG8-1 with drought-tolerant characteristics suited for breeding programs.
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16
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Sakamoto W. Editorial Feature: Meet the PCP Editor-In-Chief-Wataru Sakamoto. PLANT & CELL PHYSIOLOGY 2021; 62:222-223. [PMID: 33493292 DOI: 10.1093/pcp/pcab003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Affiliation(s)
- Wataru Sakamoto
- Okayama University, Institute of Plant Science and Resources
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17
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Nakamura S, Hagihara S, Otomo K, Ishida H, Hidema J, Nemoto T, Izumi M. Autophagy Contributes to the Quality Control of Leaf Mitochondria. PLANT & CELL PHYSIOLOGY 2021; 62:229-247. [PMID: 33355344 PMCID: PMC8112837 DOI: 10.1093/pcp/pcaa162] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Accepted: 12/05/2020] [Indexed: 05/11/2023]
Abstract
In autophagy, cytoplasmic components of eukaryotic cells are transported to lysosomes or the vacuole for degradation. Autophagy is involved in plant tolerance to the photooxidative stress caused by ultraviolet B (UVB) radiation, but its roles in plant adaptation to UVB damage have not been fully elucidated. Here, we characterized organellar behavior in UVB-damaged Arabidopsis (Arabidopsis thaliana) leaves and observed the occurrence of autophagic elimination of dysfunctional mitochondria, a process termed mitophagy. Notably, Arabidopsis plants blocked in autophagy displayed increased leaf chlorosis after a 1-h UVB exposure compared to wild-type plants. We visualized autophagosomes by labeling with a fluorescent protein-tagged autophagosome marker, AUTOPHAGY8 (ATG8), and found that a 1-h UVB treatment led to increased formation of autophagosomes and the active transport of mitochondria into the central vacuole. In atg mutant plants, the mitochondrial population increased in UVB-damaged leaves due to the cytoplasmic accumulation of fragmented, depolarized mitochondria. Furthermore, we observed that autophagy was involved in the removal of depolarized mitochondria when mitochondrial function was disrupted by mutation of the FRIENDLY gene, which is required for proper mitochondrial distribution. Therefore, autophagy of mitochondria functions in response to mitochondrion-specific dysfunction as well as UVB damage. Together, these results indicate that autophagy is centrally involved in mitochondrial quality control in Arabidopsis leaves.
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Affiliation(s)
- Sakuya Nakamura
- Center for Sustainable Resource Science (CSRS), RIKEN, Wako, 351-0198 Japan
| | - Shinya Hagihara
- Center for Sustainable Resource Science (CSRS), RIKEN, Wako, 351-0198 Japan
| | - Kohei Otomo
- Exploratory Research Center on Life and Living Systems (ExCELLs), National Institute of Natural Sciences, Okazaki, 444-8787 Japan
- National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, 444-8787 Japan
- Department of Physiological Sciences, The Graduate University for Advanced Study (SOKENDAI), Hayama, 240-0193 Japan
- Research Institute for Electronic Science, Hokkaido University, Sapporo, 001-0020 Japan
| | - Hiroyuki Ishida
- Department of Applied Plant Science, Graduate School of Agricultural Sciences, Tohoku University, Sendai, 980-0845, Japan
| | - Jun Hidema
- Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, 980-8577, Japan
| | - Tomomi Nemoto
- Exploratory Research Center on Life and Living Systems (ExCELLs), National Institute of Natural Sciences, Okazaki, 444-8787 Japan
- National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, 444-8787 Japan
- Department of Physiological Sciences, The Graduate University for Advanced Study (SOKENDAI), Hayama, 240-0193 Japan
- Research Institute for Electronic Science, Hokkaido University, Sapporo, 001-0020 Japan
| | - Masanori Izumi
- Center for Sustainable Resource Science (CSRS), RIKEN, Wako, 351-0198 Japan
- PRESTO, Japan Science and Technology Agency, Kawaguchi, 322-0012 Japan
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18
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Nakamura S, Hagihara S, Izumi M. Mitophagy in plants. Biochim Biophys Acta Gen Subj 2021; 1865:129916. [PMID: 33932484 DOI: 10.1016/j.bbagen.2021.129916] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 04/06/2021] [Accepted: 04/26/2021] [Indexed: 12/11/2022]
Abstract
Mitochondria play a central role in primary metabolism in plants as well as in heterotrophic eukaryotes. Plants must control the quality and number of mitochondria in response to a changing environment, across cell types and developmental stages. Mitophagy is defined as the degradation of mitochondria by autophagy, an evolutionarily conserved system for the removal and recycling of intracellular components. Recent studies have highlighted the importance of mitophagy in plant stress responses. This review article summarizes our current knowledge of plant mitophagy and discusses the underlying mechanisms. In plants, chloroplasts cooperate with mitochondria for energy production, and autophagy also targets chloroplasts through a process known as chlorophagy. Advances in plant autophagy studies now allow a comparative analysis of the autophagic turnover of mitochondria and chloroplasts, via the selective degradation of their soluble proteins, fragments, or entire organelles.
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Affiliation(s)
- Sakuya Nakamura
- Center for Sustainable Resource Science (CSRS), RIKEN, 351-0198 Wako, Japan
| | - Shinya Hagihara
- Center for Sustainable Resource Science (CSRS), RIKEN, 351-0198 Wako, Japan
| | - Masanori Izumi
- Center for Sustainable Resource Science (CSRS), RIKEN, 351-0198 Wako, Japan.
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19
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Nakamura S, Izumi M. Chlorophagy does not require PLANT U-BOX4-mediated ubiquitination. PLANT SIGNALING & BEHAVIOR 2021; 16:1861769. [PMID: 33331806 PMCID: PMC7889026 DOI: 10.1080/15592324.2020.1861769] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Chloroplasts and mitochondria serve as intracellular energy production sites that are powered by the electron transport chain in their membranes. These organelles constantly accumulate damage, as their energetic reactions generate reactive oxygen species. To prevent the accumulation of damaged organelles and perturbation of cellular homeostasis, eukaryotic cells must remove damaged mitochondria and chloroplasts. Autophagy is the main route by which organelles are degraded. A type of mitochondrion-targeted autophagy known as mitophagy removes damaged mitochondria in mammalian cells; dysfunctional mitochondria that lose their membrane potential are marked by protein ubiquitination, becoming targets of selective mitophagy. Studies of the quality control system for chloroplasts in plants revealed the involvement of both autophagy and ubiquitination in the degradation of damaged chloroplasts. We recently assessed the relationship between chloroplast-associated ubiquitination mediated by PLANT U-BOX4 (PUB4) and chloroplast-targeted autophagy (chlorophagy) in the turnover of oxidatively damaged chloroplasts. Multiple assays using an Arabidopsis thaliana mutant revealed that PUB4-associated ubiquitination is dispensable for the induction of chlorophagy. Here, we describe the parallel functions of PUB4 and chlorophagy in chloroplast turnover and plant growth.
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Affiliation(s)
- Sakuya Nakamura
- Center for Sustainable Resource Science (CSRS), RIKEN, Wako, Japan
| | - Masanori Izumi
- Center for Sustainable Resource Science (CSRS), RIKEN, Wako, Japan
- CONTACT Masanori Izumi Center for Sustainable Resource Science (CSRS), RIKEN, 2-1 Hirosawa, Wako351-0198, Japan
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20
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Ito E. Mitophagy—A New Player in UV-B Damage Recovery in Plants. ACTA ACUST UNITED AC 2021; 62:226-228. [DOI: 10.1093/pcp/pcab012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 01/18/2021] [Indexed: 12/26/2022]
Affiliation(s)
- Emi Ito
- Institute for Global Leadership, Ochanomizu University, 2-1-1 Bunkyo-ku, Otsuka, Tokyo, 112-8610 Japan
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21
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Agati G, Brunetti C, Fini A, Gori A, Guidi L, Landi M, Sebastiani F, Tattini M. Are Flavonoids Effective Antioxidants in Plants? Twenty Years of Our Investigation. Antioxidants (Basel) 2020; 9:E1098. [PMID: 33182252 PMCID: PMC7695271 DOI: 10.3390/antiox9111098] [Citation(s) in RCA: 98] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 11/05/2020] [Accepted: 11/06/2020] [Indexed: 12/13/2022] Open
Abstract
Whether flavonoids play significant antioxidant roles in plants challenged by photooxidative stress of different origin has been largely debated over the last few decades. A critical review of the pertinent literature and our experimentation as well, based on a free-of-scale approach, support an important antioxidant function served by flavonoids in plants exposed to a wide range of environmental stressors, the significance of which increases with the severity of stress. On the other side, some questions need conclusive answers when the putative antioxidant functions of plant flavonoids are examined at the level of both the whole-cell and cellular organelles. This partly depends upon a conclusive, robust, and unbiased definition of "a plant antioxidant", which is still missing, and the need of considering the subcellular re-organization that occurs in plant cells in response to severe stress conditions. This likely makes our deterministic-based approach unsuitable to unveil the relevance of flavonoids as antioxidants in extremely complex biological systems, such as a plant cell exposed to an ever-changing stressful environment. This still poses open questions about how to measure the occurred antioxidant action of flavonoids. Our reasoning also evidences the need of contemporarily evaluating the changes in key primary and secondary components of the antioxidant defense network imposed by stress events of increasing severity to properly estimate the relevance of the antioxidant functions of flavonoids in an in planta situation. In turn, this calls for an in-depth analysis of the sub-cellular distribution of primary and secondary antioxidants to solve this still intricate matter.
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Affiliation(s)
- Giovanni Agati
- Institute of Applied Physics ‘Carrara’, National Research Council of Italy (CNR), Via Madonna del Piano 10, Sesto F.no, I-50019 Florence, Italy;
| | - Cecilia Brunetti
- Institute for Sustainable Plant Protection, National Research Council of Italy (CNR), Via Madonna del Piano 10, I-50019, Sesto F.no, Florence, Italy; (C.B.); (F.S.)
| | - Alessio Fini
- Department of Agriculural and Environmental Sciences - Production, Landscape, Agroenergy, University of Milan, Via Celoria 2, I-20133 Milan, Italy;
| | - Antonella Gori
- Department of Agriculture, Food, Environment and Forestry, University of Florence, Viale delle Idee 30, Sesto F.no, I-50019 Florence, Italy;
| | - Lucia Guidi
- Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, I-56124 Pisa, Italy; (L.G.); (M.L.)
| | - Marco Landi
- Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, I-56124 Pisa, Italy; (L.G.); (M.L.)
| | - Federico Sebastiani
- Institute for Sustainable Plant Protection, National Research Council of Italy (CNR), Via Madonna del Piano 10, I-50019, Sesto F.no, Florence, Italy; (C.B.); (F.S.)
| | - Massimiliano Tattini
- Institute for Sustainable Plant Protection, National Research Council of Italy (CNR), Via Madonna del Piano 10, I-50019, Sesto F.no, Florence, Italy; (C.B.); (F.S.)
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22
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Huo L, Sun X, Guo Z, Jia X, Che R, Sun Y, Zhu Y, Wang P, Gong X, Ma F. MdATG18a overexpression improves basal thermotolerance in transgenic apple by decreasing damage to chloroplasts. HORTICULTURE RESEARCH 2020; 7:21. [PMID: 32140230 PMCID: PMC7049305 DOI: 10.1038/s41438-020-0243-2] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 01/01/2020] [Accepted: 01/04/2020] [Indexed: 05/06/2023]
Abstract
High temperature is an abiotic stress factor that threatens plant growth and development. Autophagy in response to heat stress involves the selective removal of heat-induced protein complexes. Previously, we showed that a crucial autophagy protein from apple, MdATG18a, has a positive effect on drought tolerance. In the present study, we treated transgenic apple (Malus domestica) plants overexpressing MdATG18a with high temperature and found that autophagy protected them from heat stress. Overexpression of MdATG18a in apple enhanced antioxidase activity and contributed to the production of increased beneficial antioxidants under heat stress. Transgenic apple plants exhibited higher photosynthetic capacity, as shown by the rate of CO2 assimilation, the maximum photochemical efficiency of photosystem II (PSII), the effective quantum yield, and the electron transport rates in photosystems I and II (PSI and PSII, respectively). We also detected elevated autophagic activity and reduced damage to chloroplasts in transgenic plants compared to WT plants. In addition, the transcriptional activities of several HSP genes were increased in transgenic apple plants. In summary, we propose that autophagy plays a critical role in basal thermotolerance in apple, primarily through a combination of enhanced antioxidant activity and reduced chloroplast damage.
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Affiliation(s)
- Liuqing Huo
- State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling, 712100 Shaanxi China
| | - Xun Sun
- Center of Pear Engineering Technology Research, State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095 China
| | - Zijian Guo
- State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling, 712100 Shaanxi China
| | - Xin Jia
- State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling, 712100 Shaanxi China
| | - Runmin Che
- State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling, 712100 Shaanxi China
| | - Yiming Sun
- State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling, 712100 Shaanxi China
| | - Yanfei Zhu
- State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling, 712100 Shaanxi China
| | - Ping Wang
- State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling, 712100 Shaanxi China
| | - Xiaoqing Gong
- State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling, 712100 Shaanxi China
| | - Fengwang Ma
- State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling, 712100 Shaanxi China
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23
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Mayta ML, Hajirezaei MR, Carrillo N, Lodeyro AF. Leaf Senescence: The Chloroplast Connection Comes of Age. PLANTS (BASEL, SWITZERLAND) 2019; 8:E495. [PMID: 31718069 PMCID: PMC6918220 DOI: 10.3390/plants8110495] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 11/05/2019] [Accepted: 11/06/2019] [Indexed: 12/15/2022]
Abstract
Leaf senescence is a developmental process critical for plant fitness, which involves genetically controlled cell death and ordered disassembly of macromolecules for reallocating nutrients to juvenile and reproductive organs. While natural leaf senescence is primarily associated with aging, it can also be induced by environmental and nutritional inputs including biotic and abiotic stresses, darkness, phytohormones and oxidants. Reactive oxygen species (ROS) are a common thread in stress-dependent cell death and also increase during leaf senescence. Involvement of chloroplast redox chemistry (including ROS propagation) in modulating cell death is well supported, with photosynthesis playing a crucial role in providing redox-based signals to this process. While chloroplast contribution to senescence received less attention, recent findings indicate that changes in the redox poise of these organelles strongly affect senescence timing and progress. In this review, the involvement of chloroplasts in leaf senescence execution is critically assessed in relation to available evidence and the role played by environmental and developmental cues such as stress and phytohormones. The collected results indicate that chloroplasts could cooperate with other redox sources (e.g., mitochondria) and signaling molecules to initiate the committed steps of leaf senescence for a best use of the recycled nutrients in plant reproduction.
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Affiliation(s)
- Martín L. Mayta
- Instituto de Biología Molecular y Celular de Rosario (IBR-UNR/CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario (UNR), 2000 Rosario, Argentina;
| | - Mohammad-Reza Hajirezaei
- Leibniz Institute of Plant Genetics and Crop Plant Research, OT Gatersleben, Corrensstrasse, D-06466 Stadt Seeland, Germany;
| | - Néstor Carrillo
- Instituto de Biología Molecular y Celular de Rosario (IBR-UNR/CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario (UNR), 2000 Rosario, Argentina;
| | - Anabella F. Lodeyro
- Instituto de Biología Molecular y Celular de Rosario (IBR-UNR/CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario (UNR), 2000 Rosario, Argentina;
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24
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Shull TE, Kurepa J, Smalle JA. Anatase TiO 2 Nanoparticles Induce Autophagy and Chloroplast Degradation in Thale Cress ( Arabidopsis thaliana). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:9522-9532. [PMID: 31356742 DOI: 10.1021/acs.est.9b01648] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The extensive use of TiO2 nanoparticles and their subsequent release into the environment have posed an important question about the effects of this nanomaterial on ecosystems. Here, we analyzed the link between the damaging effects of reactive oxygen species generated by TiO2 nanoparticles and autophagy, a housekeeping mechanism that removes damaged cellular constituents. We show that TiO2 nanoparticles induce autophagy in the plant model system Arabidopsis thaliana and that autophagy is an important mechanism for managing TiO2 nanoparticle-induced oxidative stress. Additionally, we find that TiO2 nanoparticles induce oxidative stress predominantly in chloroplasts and that this chloroplastic stress is mitigated by autophagy. Collectively, our results suggest that photosynthetic organisms are particularly susceptible to TiO2 nanoparticle toxicity.
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Affiliation(s)
- Timothy E Shull
- Department of Plant and Soil Sciences , University of Kentucky , Lexington , Kentucky 40546 United States
| | - Jasmina Kurepa
- Department of Plant and Soil Sciences , University of Kentucky , Lexington , Kentucky 40546 United States
| | - Jan A Smalle
- Department of Plant and Soil Sciences , University of Kentucky , Lexington , Kentucky 40546 United States
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25
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Johnston IG. Tension and Resolution: Dynamic, Evolving Populations of Organelle Genomes within Plant Cells. MOLECULAR PLANT 2019; 12:764-783. [PMID: 30445187 DOI: 10.1016/j.molp.2018.11.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Revised: 10/25/2018] [Accepted: 11/07/2018] [Indexed: 06/09/2023]
Abstract
Mitochondria and plastids form dynamic, evolving populations physically embedded in the fluctuating environment of the plant cell. Their evolutionary heritage has shaped how the cell controls the genetic structure and the physical behavior of its organelle populations. While the specific genes involved in these processes are gradually being revealed, the governing principles underlying this controlled behavior remain poorly understood. As the genetic and physical dynamics of these organelles are central to bioenergetic performance and plant physiology, this challenges both fundamental biology and strategies to engineer better-performing plants. This article reviews current knowledge of the physical and genetic behavior of mitochondria and chloroplasts in plant cells. An overarching hypothesis is proposed whereby organelles face a tension between genetic robustness and individual control and responsiveness, and different species resolve this tension in different ways. As plants are immobile and thus subject to fluctuating environments, their organelles are proposed to favor individual responsiveness, sacrificing genetic robustness. Several notable features of plant organelles, including large genomes, mtDNA recombination, fragmented organelles, and plastid/mitochondrial differences may potentially be explained by this hypothesis. Finally, the ways that quantitative and systems biology can help shed light on the plethora of open questions in this field are highlighted.
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Affiliation(s)
- Iain G Johnston
- School of Biosciences, University of Birmingham, Birmingham, UK; Birmingham Institute for Forest Research, University of Birmingham, Birmingham, UK.
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26
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Yoon SH, Chung T. Protein and RNA Quality Control by Autophagy in Plant Cells. Mol Cells 2019; 42:285-291. [PMID: 31091554 PMCID: PMC6530645 DOI: 10.14348/molcells.2019.0011] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 03/03/2019] [Accepted: 03/19/2019] [Indexed: 11/27/2022] Open
Abstract
Eukaryotic cells use conserved quality control mechanisms to repair or degrade defective proteins, which are synthesized at a high rate during proteotoxic stress. Quality control mechanisms include molecular chaperones, the ubiquitin-proteasome system, and autophagic machinery. Recent research reveals that during autophagy, membrane-bound organelles are selectively sequestered and degraded. Selective autophagy is also critical for the clearance of excess or damaged protein complexes (e.g., proteasomes and ribosomes) and membrane-less compartments (e.g., protein aggregates and ribonucleoprotein granules). As sessile organisms, plants rely on quality control mechanisms for their adaptation to fluctuating environments. In this mini-review, we highlight recent work elucidating the roles of selective autophagy in the quality control of proteins and RNA in plant cells. Emphasis will be placed on selective degradation of membrane-less compartments and protein complexes in the cytoplasm. We also propose possible mechanisms by which defective proteins are selectively recognized by autophagic machinery.
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Affiliation(s)
- Seok Ho Yoon
- Department of Biological Sciences, Pusan National University, Busan 46241,
Korea
| | - Taijoon Chung
- Department of Biological Sciences, Pusan National University, Busan 46241,
Korea
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27
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Izumi M, Nakamura S, Li N. Autophagic Turnover of Chloroplasts: Its Roles and Regulatory Mechanisms in Response to Sugar Starvation. FRONTIERS IN PLANT SCIENCE 2019; 10:280. [PMID: 30967883 PMCID: PMC6439420 DOI: 10.3389/fpls.2019.00280] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Accepted: 02/20/2019] [Indexed: 05/29/2023]
Abstract
Photosynthetic reactions in chloroplasts convert atmospheric carbon dioxide into starch and soluble sugars during the day. Starch, a transient storage form of sugar, is broken down into sugars as a source for respiratory energy production at night. Chloroplasts thus serve as the main sites of sugar production for photoautotrophic plant growth. Autophagy is an evolutionarily conserved intracellular process in eukaryotes that degrades organelles and proteins. Numerous studies have shown that autophagy is actively induced in sugar-starved plants. When photosynthetic sugar production is inhibited by environmental cues, chloroplasts themselves may become an attractive alternative energy source to sugars via their degradation. Here, we summarize the process of autophagic turnover of chloroplasts and its roles in plants in response to sugar starvation. We hypothesize that piecemeal-type chloroplast autophagy is specifically activated in plants in response to sugar starvation.
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Affiliation(s)
- Masanori Izumi
- Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai, Japan
- Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
- PRESTO, Japan Science and Technology Agency, Kawaguchi, Japan
| | - Sakuya Nakamura
- Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Nan Li
- Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai, Japan
- College of Life Sciences, Liaocheng University, Liaocheng, China
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28
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Avin-Wittenberg T. Autophagy and its role in plant abiotic stress management. PLANT, CELL & ENVIRONMENT 2019; 42:1045-1053. [PMID: 29998609 DOI: 10.1111/pce.13404] [Citation(s) in RCA: 106] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 06/15/2018] [Accepted: 06/18/2018] [Indexed: 05/02/2023]
Abstract
Being unable to move, plants are regularly exposed to changing environmental conditions, among which various types of abiotic stress, such as heat, drought, salt, and so forth. These might have deleterious effects on plant performance and yield. Plants thus need to adapt using appropriate stress responses. One of the outcomes of abiotic stress is the need to degrade and recycle damaged proteins and organelles. Autophagy is a conserved eukaryotic mechanism functioning in the degradation of proteins, protein aggregates, and whole organelles. It was previously shown to have a role in plant abiotic stress. This review will describe the current knowledge regarding the involvement of autophagy in plant abiotic stress response, mechanisms functioning in autophagy induction during stress, and possible direction for future research.
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Affiliation(s)
- Tamar Avin-Wittenberg
- Department of Plant and Environmental Sciences, Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
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29
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Tamary E, Nevo R, Naveh L, Levin‐Zaidman S, Kiss V, Savidor A, Levin Y, Eyal Y, Reich Z, Adam Z. Chlorophyll catabolism precedes changes in chloroplast structure and proteome during leaf senescence. PLANT DIRECT 2019; 3:e00127. [PMID: 31245770 PMCID: PMC6508775 DOI: 10.1002/pld3.127] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Revised: 02/25/2019] [Accepted: 02/26/2019] [Indexed: 05/18/2023]
Abstract
The earliest visual changes of leaf senescence occur in the chloroplast as chlorophyll is degraded and photosynthesis declines. Yet, a comprehensive understanding of the sequence of catabolic events occurring in chloroplasts during natural leaf senescence is still missing. Here, we combined confocal and electron microscopy together with proteomics and biochemistry to follow structural and molecular changes during Arabidopsis leaf senescence. We observed that initiation of chlorophyll catabolism precedes other breakdown processes. Chloroplast size, stacking of thylakoids, and efficiency of PSII remain stable until late stages of senescence, whereas the number and size of plastoglobules increase. Unlike catabolic enzymes, whose level increase, the level of most proteins decreases during senescence, and chloroplast proteins are overrepresented among these. However, the rate of their disappearance is variable, mostly uncoordinated and independent of their inherent stability during earlier developmental stages. Unexpectedly, degradation of chlorophyll-binding proteins lags behind chlorophyll catabolism. Autophagy and vacuole proteins are retained at relatively high levels, highlighting the role of extra-plastidic degradation processes especially in late stages of senescence. The observation that chlorophyll catabolism precedes all other catabolic events may suggest that this process enables or signals further catabolic processes in chloroplasts.
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Affiliation(s)
- Eyal Tamary
- The Robert H. Smith Institute of Plant Sciences and Genetics in AgricultureThe Hebrew UniversityRehovotIsrael
| | - Reinat Nevo
- Department of Biomolecular SciencesWeizmann Institute of ScienceRehovotIsrael
| | - Leah Naveh
- The Robert H. Smith Institute of Plant Sciences and Genetics in AgricultureThe Hebrew UniversityRehovotIsrael
| | - Smadar Levin‐Zaidman
- Department of Chemical Research SupportWeizmann Institute of ScienceRehovotIsrael
| | - Vladimir Kiss
- Department of Biomolecular SciencesWeizmann Institute of ScienceRehovotIsrael
| | - Alon Savidor
- de Botton Institute for Protein ProfilingThe Nancy and Stephen Grand Israel National Center for Personalized MedicineWeizmann Institute of ScienceRehovotIsrael
| | - Yishai Levin
- de Botton Institute for Protein ProfilingThe Nancy and Stephen Grand Israel National Center for Personalized MedicineWeizmann Institute of ScienceRehovotIsrael
| | - Yoram Eyal
- Institute of Plant SciencesThe Volcani Center ARORishon LeZionIsrael
| | - Ziv Reich
- Department of Biomolecular SciencesWeizmann Institute of ScienceRehovotIsrael
| | - Zach Adam
- The Robert H. Smith Institute of Plant Sciences and Genetics in AgricultureThe Hebrew UniversityRehovotIsrael
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30
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Zhuang X, Jiang L. Chloroplast Degradation: Multiple Routes Into the Vacuole. FRONTIERS IN PLANT SCIENCE 2019; 10:359. [PMID: 30972092 PMCID: PMC6443708 DOI: 10.3389/fpls.2019.00359] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2018] [Accepted: 03/07/2019] [Indexed: 05/05/2023]
Abstract
Chloroplasts provide energy for all plants by producing sugar during photosynthesis. To adapt to various environmental and developmental cues, plants have developed specific strategies to control chloroplast homeostasis in plant cells, including chloroplast degradation during leaf senescence and the transition of chloroplasts into other types of plastids during the day-night cycle. In recent years, autophagy has emerged as an essential mechanism for selective degradation of chloroplast materials (also known as chlorophagy) in the vacuole. Different types of membrane structures have been implicated to involve in the delivery of distinct chloroplast contents. Here we provide a current overview on chlorophagy and discuss the possible chloroplast receptors and upstream signals in this process.
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Affiliation(s)
- Xiaohong Zhuang
- School of Life Sciences, Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Hong Kong, China
- The Chinese University of Hong Kong Shenzhen Research Institute, Shenzhen, China
- *Correspondence: Xiaohong Zhuang,
| | - Liwen Jiang
- School of Life Sciences, Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Hong Kong, China
- The Chinese University of Hong Kong Shenzhen Research Institute, Shenzhen, China
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31
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Nakamura S, Izumi M. Chlorophagy is ATG gene-dependent microautophagy process. PLANT SIGNALING & BEHAVIOR 2018; 14:1554469. [PMID: 30574829 PMCID: PMC6351093 DOI: 10.1080/15592324.2018.1558679] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2018] [Accepted: 12/10/2018] [Indexed: 05/27/2023]
Abstract
Autophagy delivers cytosolic components to lysosomes and the vacuole for degradation. This pathway prevents starvation through bulk degradation and recycling of cytoplasmic components, and maintains cellular homeostasis through selective elimination of damaged proteins and organelles. Autophagic delivery processes are categorized into three types: macroautophagy, microautophagy, and chaperone-mediated autophagy. During macroautophagy, nascent, double membrane-bound vesicles termed autophagosomes sequester a portion of cytoplasm and deliver it to the vacuole/lysosomes. Molecular genetic studies in budding yeasts have identified a set of AUTOPHAGY (ATG) genes required for autophagosome formation. Although microautophagy involves the direct lysosomal/vacuolar engulfment and incorporation of a target into the lumen rather than the formation of autophagosomes, the membrane dynamics and possible roles of ATGs during microautophagy are under investigation. Our recent study revealed an ATG-dependent microautophagy process in plants, during which chloroplasts damaged by high visible light (HL) are selectively eliminated. Here, we discuss the membrane dynamics of the plant microautophagy that enables the transport of whole chloroplasts into the vacuole.
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Affiliation(s)
- Sakuya Nakamura
- Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Masanori Izumi
- Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
- Creative Interdisciplinary Research Division, Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai, Japan
- PRESTO, Japan Science and Technology Agency, Kawaguchi, Japan
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32
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Izumi M, Ishida H. An additional role for chloroplast proteins-an amino acid reservoir for energy production during sugar starvation. PLANT SIGNALING & BEHAVIOR 2018; 14:1552057. [PMID: 30507341 PMCID: PMC6351091 DOI: 10.1080/15592324.2018.1552057] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Revised: 11/14/2018] [Accepted: 11/18/2018] [Indexed: 06/09/2023]
Abstract
Autophagy is an evolutionarily conserved system that degrades intracellular components including proteins and organelles, and is important in the adaptive response to starvation in various eukaryotic organisms. Plant chloroplasts convert light energy into chemical energy and assimilate atmospheric carbon dioxide (CO2) for carbohydrate production through photosynthesis reactions. We previously described an autophagy process for chloroplast degradation, during which a portion of chloroplasts are mobilized into the vacuole via autophagic vesicles termed Rubisco-containing bodies. Our recent study demonstrated that the activation of autophagy in photoassimilate-limited leaves is required for the production of free amino acids (AAs) as an alternative energy source. The catabolism of free branched-chain amino acids (BCAAs) is particularly important for survival under starvation conditions. These recent findings suggest an additional role for chloroplasts as a reservoir of AA when photosynthetic energy production is limited.
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Affiliation(s)
- Masanori Izumi
- Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai, Japan
- Department of Molecular and Chemical Life Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
- PRESTO, Japan Science and Technology Agency, Kawaguchi, Japan
| | - Hiroyuki Ishida
- Department of Applied Plant Science, Graduate School of Agricultural Science, Tohoku University, Sendai, Japan
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33
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Naumann M, Hubberten HM, Watanabe M, Hänsch R, Schöttler MA, Hoefgen R. Sulfite Reductase Co-suppression in Tobacco Reveals Detoxification Mechanisms and Downstream Responses Comparable to Sulfate Starvation. FRONTIERS IN PLANT SCIENCE 2018; 9:1423. [PMID: 30374361 PMCID: PMC6196246 DOI: 10.3389/fpls.2018.01423] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Accepted: 09/07/2018] [Indexed: 05/30/2023]
Abstract
Sulfite reductase (SIR) is a key enzyme in higher plants in the assimilatory sulfate reduction pathway. SIR, being exclusively localized in plastids, catalyzes the reduction of sulfite (SO3 2-) to sulfide (S2-) and is essential for plant life. We characterized transgenic plants leading to co-suppression of the SIR gene in tobacco (Nicotiana tabacum cv. Samsun NN). Co-suppression resulted in reduced but not completely extinguished expression of SIR and in a reduction of SIR activity to about 20-50% of the activity in control plants. The reduction of SIR activity caused chlorotic and necrotic phenotypes in tobacco leaves, but with varying phenotype strength even among clones and increasing from young to old leaves. In transgenic plants compared to control plants, metabolite levels upstream of SIR accumulated, such as sulfite, sulfate and thiosulfate. The levels of downstream metabolites were reduced, such as cysteine, glutathione (GSH) and methionine. This metabolic signature resembles a sulfate deprivation phenotype as corroborated by the fact that O-acetylserine (OAS) accumulated. Further, chlorophyll contents, photosynthetic electron transport, and the contents of carbohydrates such as starch, sucrose, fructose, and glucose were reduced. Amino acid compositions were altered in a complex manner due to the reduction of contents of cysteine, and to some extent methionine. Interestingly, sulfide levels remained constant indicating that sulfide homeostasis is crucial for plant performance and survival. Additionally, this allows concluding that sulfide does not act as a signal in this context to control sulfate uptake and assimilation. The accumulation of upstream compounds hints at detoxification mechanisms and, additionally, a control exerted by the downstream metabolites on the sulfate uptake and assimilation system. Co-suppression lines showed increased sensitivity to additionally imposed stresses probably due to the accumulation of reactive compounds because of insufficient detoxification in combination with reduced GSH levels.
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Affiliation(s)
- Marcel Naumann
- Max Planck Institute of Molecular Plant Physiology, Potsdam, Germany
- Division of Quality of Plant Products, Department of Crop Sciences, University of Göttingen, Göttingen, Germany
| | | | - Mutsumi Watanabe
- Max Planck Institute of Molecular Plant Physiology, Potsdam, Germany
- Nara Institute of Science and Technology, Ikoma, Japan
| | - Robert Hänsch
- Department of Plant Biology, Technische Universität Braunschweig, Braunschweig, Germany
| | | | - Rainer Hoefgen
- Max Planck Institute of Molecular Plant Physiology, Potsdam, Germany
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