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Interplay between ABA and GA Modulates the Timing of Asymmetric Cell Divisions in the Arabidopsis Root Ground Tissue

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molecular plant 2016年第6期9卷 870-884页

作者： Shin Ae Lee Sejeong Jang Eun Kyung Yoon Jung-Ok Heo Kwang Suk Chang Ji Won Choi Souvik Dhar Gyuree Kim Jeong-Eun Choe Jae Bok Heo Chian Kwon Jae-Heung Ko Yong-Sic Hwang Jun Lim Department of Systems biotechnology Konkuk University Seour 05029 Korea Department of molecular biotechnology Dong-A University Busan 49201 Korea Department of molecular Biology Dankook University Yongin 16890 Korea Department of plant and Environmental New Resources Kyung Hee University Yongin 17104 Korea These authors contributed equally to this article. present address: The Sainsbury Laboratory University of Cambridge Cambridge CB2 1LR United Kingdom present address: Department of Life Science Research Institute for Natural Sciences Hanyang University Seoul 04763 Korea

In multicellular organisms, controlling the timing and extent of asymmetric cell divisions （ACDs） is crucial for correct patterning. During post-embryonic root development in Arabidopsis thaliana, ground tissue （GT） maturation involves an additional ACD of the endodermis, which generates two different tissues： the endo- dermis （inner） and the middle cortex （outer）. It has been reported that the abscisic acid （ABA） and gibberellin （GA） pathways are involved in middle cortex （MC） formation. However, the molecular mechanisms under- lying the interaction between ABA and GA during GT maturation remain largely unknown. Through transcriptome analyses, we identified a previously uncharacterized C2H2-type zinc finger gene, whose expression is regulated by GA and ABA, thus named GAZ （GA- AND ABA-RESPONSIVE ZINC FINGER）. Seedlings ectopically overexpressing GAZ （GAZ-OX） were sensitive to ABA and GA during MC formation, whereas GAZ-SRDX and RNAi seedlings displayed opposite phenotypes. In addition, our results indicated that GAZ was involved in the transcriptional regulation of ABA and GA homeostasis. In agreement with pre- vious studies that ABA and GA coordinate to control the timing of MC formation, we also confirmed the unique interplay between ABA and GA and identified factors and regulatory networks bridging the two hor- mone pathways during GT maturation of the Arabidopsis root.

关键词： ABA GA GRAS ground tissue root development transcription factor

Identification and Preliminary Characterization of a New Chemical Affecting Glucosyltransferase Activities Involved in plant Cell Wall Biosynthesis

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molecular plant 2008年第6期1卷 977-989页

作者： Olga Zabotina Erik Maim Georgia Drakakaki Vincent Bulone Natasha Raikhel Institute for Integrative Genome Biology Center for Plant Cell Biology and Department of Botany and Plant Sciences University of California Riverside CA92521 USA School of biotechnology Royal Institute of Technology (KTH) AlbaNova University Center Stockholm SE-106 91 Sweden present address: Department of Biochemistry Biophysics and Molecular Biology Iowa State University Ames IA 50014 USA

Chemical genetics as a part of chemical genomics is a powerful and fast developing approach to dissect biological processes that may be difficult to characterize using conventional genetics because of gene redundancy or lethality and, in the case of polysaccharide biosynthesis, plant flexibility. Polysaccharide synthetic enzymes are located in two main compartments--the Golgi apparatus and plasma membrane-and can be studied in vitro using membrane fractions. Here, we first developed a high-throughput assay that allowed the screening of a library of chemicals with a potential effect on glycosyltransferase activities. Out of the 4800 chemicals screened for their effect on Golgi glucosyltransferases, 66 compounds from the primary screen had an effect on carbohydrate biosynthesis. Ten of these compounds were confirmed to inhibit glucose incorporation after a second screen. One compound exhibiting a strong inhibition effect （ID 6240780 named chemical A） was selected and further studied. It reversibly inhibits the transfer of glucose from UDP-glucose by Golgi membranes, but activates the plasma membrane-bound callose synthase. The inhibition effect is dependent on the chemical structure of the compound, which does not affect endomembrane morphology of the plant cells, but causes changes in cell wall composition. Chemical A represents a novel drug with a great potential for the study of the mechanisms of Golgi and plasma membrane-bound glucosyltransferases.

关键词： cell walls callose synthase chemical screening and identification glycosyltransferase Golgi plasma membrane

Arabidopsis STAY-GREEN2 Is a Negative Regulator of Chlorophyll Degradation during Leaf Senescence

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molecular plant 2014年第8期7卷 1288-1302页

作者： Yasuhito Sakuraba So-Yon Park Ye-Sol Kim Seung-Hyun Wang Soo-Cheul Yoo Stefan Hortensteiner Nam-Chon Paek Department of plant Science Plant Genomics and Breeding Institute Research Institute of Agriculture and Life Sciences Seoul NationalUniversity Seoul 151-921 Korea present address: Department of plant Pathology Physiology and Weed Science Virginia Tech Blacksburg VA 24061 USA present address: Advanced Radiation Technology Institute Korea Atomic Energy Research Institute Jeongeup 580-185 Korea Department of plant & Environmental Science Hankyong National University Ansung 456-749 Korea Institute of plant Biology University of Zurich CH-8008 Zurich Switzerland

Chlorophyll （Chl） degradation causes leaf yellowing during senescence or under stress conditions. For Chl breakdown, STAY-GREEN1 （SGR1） interacts with Chl catabolic enzymes （CCEs） and light-harvesting complex II （LHCII） at the thylakoid membrane, possibly to allow metabolic channeling of potentially phototoxic Chl breakdown intermediates. Among these Chl catabolic components, SGR1 acts as a key regulator of leaf yellowing. In addition to SGR1 （At4g22920）, the Arabidopsis thaliana genome contains an additional homolog, SGR2 （At4g11910）, whose biological function remains elusive. Under senescence-inducing conditions, SGR2 expression is highly up-regulated, similarly to SGR1 expression. Here we show that SGR2 function counteracts SGR1 activity in leaf Chl degradation; SGR2-overexpressing plants stayed green and the sgr2-1 knockout mutant exhibited early leaf yellowing under age-, dark-, and stress-induced senescence conditions. Like SGR1, SGR2 interacted with LHCII but, in contrast to SGR1, SGR2 interactions with CCEs were very limited. Furthermore, SGR1 and SGR2 formed homo- or heterodimers, strongly suggesting a role for SGR2 in negatively regulat- ing Chl degradation by possibly interfering with the proposed CCE-recruiting function of SGR1. Our data indicate an antagonistic evolution of the functions of SGR1 and SGR2 in Arabidopsis to balance Chl catabolism in chloroplasts with the dismantling and remobilizing of other cellular components in senescing leaf cells.

关键词： Arabidopsis thaliana stay-green SGR1 SGR2 chlorophyll degradation leaf senescence abiotic stress.

Subcellular Redistribution of Root Aquaporins nduced by Hydrogen Peroxide

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molecular plant 2015年第7期8卷 1103-1114页

作者： Michael M. Wudick Xiaojuan Li Valeria Valentini Niko Geldner Joanne Chory Jinxing Lin Christophe Maurel Doan-Trung Luu Biochimie et Physiologie Moleculaire des plantes Institut de Biologie Integrative des Plantes UMR 5004 CNRS/UMR 0386 INRA/Montpellier SupAgro/Universit~Montpellier 2 2 Place Viala F-34060 Montpellier Cedex 2 France Key Laboratory of plant molecular physiology Institute of Botany Chinese Academy of Sciences Beijing 100093 China Department of plant molecular Biology Universite de Lausanne 1015 Lausanne Switzerland plant molecular and Cellular Biology Laboratory The Salk Institute La Jolla CA 92037 USA present address: Department of Cell Biology and molecular Genetics University of Maryland College Park MD 20742-5815 USA present address: Instituto Gulbenkian de Ciencia 2780-156 Oeiras Portugal

Aquaporins are water channel proteins that mediate the fine-tuning of cell membrane water permeability during development or in response to environmental stresses. The present work focuses on the oxidative stress-induced redistribution of plasma membrane intrinsic protein （PIP） aquaporins from the plasma membrane （PM） to intracellular membranes. This process was investigated in the Arabidopsis root. Su- crose density gradient centrifugation showed that exposure of roots to 0.5 mM H2O2 induces significant depletion in PM fractions of several abundant PIP homologs after 15 rain. Analyses by single-particle tracking and fluorescence correlative spectroscopy showed that, in the PM of epidermal cells, H2O2 treat- ment induces an increase in lateral motion and a reduction in the density of a fluorescently tagged form of the prototypal AtPIP2;1 isoform, respectively. Co-expression analyses of AtPIP2;1 with endomembrane markers revealed that H2O2 triggers AtPIP2;1 accumulation in the late endosomal compartments. Life- time analyses established that the high stability of PIPs was maintained under oxidative stress conditions, suggesting that H2O2 triggers a mechanism for intracellular sequestration of PM aquaporins without further degradation. In addition to information on cellular regulation of aquaporins, this study provides novel and complementary insights into the dynamic remodeling of plant internal membranes during oxida- tive stress responses.

关键词： Arabidopsis aquaporin stress reactive oxygen species root

Spatial H202 Signaling Specificity： H202 from Chloroplasts and Peroxisomes Modulates the plant Transcriptome Differentially

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molecular plant 2014年第7期7卷 1191-1210页

作者： Nasser Sewelam Nils Jaspert Katrien Van Der Kelen Vanesa B. Tognetti Jessica Schmitz Henning Frerigmann Elia Stahl Frank Van Breusegem Veronica G. Maurino Institut of Developmental and molecular Biology of plants Plant Molecular Physiology and Biotechnology Group Heinrich-Heine-Universit~t Universit~tsstraBe 1 40225 D~sseldorf Germany Botany Department Faculty of Science Tanta University 31527 Tanta Egypt Department of plant Systems Biology VIB and Department of Plant Biotechnology and Bioinformatics Ghent UniversityTechnologiepark 927 B-9052 Gent Belgium present address: Mendel Centre for plant Genomics and Proteomics CEITEC--Central European Institute of Technology MasarykUniversity Kamenice 5 CZ-62500 Brno Czech Republic Botanical Institute Cologne Biocenter University of Cologne 50674 Cologne Germany Cluster of Excellence on plant Sciences (CEPLAS) 40225 Dusseldorf and 50674 Cologne Germany molecular Ecophysiology of plants Heinrich-Heine-Universitat Universitatsstraf3e 1 40225 D~sseldorf Germany

Hydrogen peroxide （H2O2） operates as a signaling molecule in eukaryotes, but the specificity of its signal- ing capacities remains largely unrevealed. Here, we analyzed whether a moderate production of H2O2 from two different plant cellular compartments has divergent effects on the plant transcriptome. Arabidopsis thaliana overexpressing glycolate oxidase in the chloroplast （Fahnenstich et al., 2008; Balazadeh et al., 2012） and plants deficient in peroxisomal catalase （Queval et al., 2007; Inze et al., 2012） were grown under non-photorespiratory conditions and then transferred to photorespiratory conditions to foster the production of H202 in both organelles. We show that H202 originating in a specific organelle induces two types of responses： one that integrates signals independently from the subcellular site of H202 production and another that is dependent on the H2O2 production site. H2O2 produced in peroxisomes induces transcripts involved in protein repair responses, while H2O2 produced in chloroplasts induces early signaling responses, including transcription factors and biosynthetic genes involved in production of secondary signaling messengers. There is a significant bias towards the induction of genes involved in responses to wounding and pathogen attack by chloroplas- tic-produced H202, including indolic glucosinolates-, camalexin-, and stigmasterol-biosynthetic genes. These transcriptional responses were accompanied by the accumulation of 4-methoxy-indol-3-ylmethyl glucosinolate and stigmasterol.

关键词： hydrogen peroxide reactive oxygen species glycolate oxidase catalase photorespiration oxidative signaling.

Histone Lysine Methyltransferase SDG8 Is Involved in Brassinosteroid-Regulated Gene Expression in Arabidopsis thaliana

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molecular plant 2014年第8期7卷 1303-1315页

作者： Xiaolei Wang Jiani Chen Zhouli Xie Sanzhen Liu Trevor Nolan Huaxun Ye Mingcai Zhang Hongqing Guo Patrick S. Schnable Zhaohu Li Yanhai Yin State Key Laboratory of plant physiology and Biochemistry Department of Agronomy College of Agronomy and Biotechnology ChinaAgricultural University Beijing 100193 PR China Department of Genetics Development and Cell Biology Iowa State University Ames IA 50011 USA Department of Agronomy Iowa State University Ames IA 50011 USA present address: Department of plant Pathology Kansas State University Manhattan KS 66506-5502 USA present address: Du Pont Pioneer Inc. Johnston IA USA Data2Bio LLC Ames IA 50011-3650 USA

The plant steroid hormones, brassinosteroids （BRs）, play important roles in plant growth, development, and responses to environmental stresses. BRs signal through receptors localized to the plasma membrane and other signaling components to regulate the BES1/BZR1 family of transcription factors, which modulates the expression of thousands of genes. How BESl/BZR1 and their interacting proteins function to regulate the large number of genes are not com- pletely understood. Here we report that histone lysine methyltransferase SDG8, implicated in histone 3 lysine 36 diand trimethylation （H3K36me2 and me3）, is involved in BR-regulated gene expression. BES1 interacts with SDG8, directly or indirectly through IWSl, a transcription elongation factor involved in BR-regulated gene expression. The knockout mutant sdg8 displays a reduced growth phenotype with compromised BR responses. Global gene expression studies demonstrated that, while BR regulates about 5000 genes in wild-type plants, the hormone regulates fewer than 700 genes in sdg8 mutant. In addition, more than half of BR-regulated genes are differentially affected in sdg8 mutant. A Chromatin Immunoprecipitation （CHIP） experiment showed that H3K36me3 is reduced in BR-regulated genes in the sdg8 mutant. Based on these results, we propose that SDG8 plays an essential role in mediating BR-regulated gene expression. Our results thus reveal a major mechanism by which histone modifications dictate hormonal regulation of gene expression.

关键词： brassinosteroid histone modifications gene regulation.

Inhibition of the Ubiquitin-Proteasome Pathway Alters Cellular Levels of Nitric Oxide in Tomato Seedlings

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molecular plant 2010年第5期3卷 854-869页

作者： Sangeeta Negi Parankusam Santisree Eros Vasil Kharshiing Rameshwar Sharma School of Life Sciences University of Hyderabad Hyderabad-500 046 India present address: Donald Danforth plant Science Centre 975 N. Warson Rd St Louis MO 63132 USA present address: St Edmunds College Shillong Meghalaya India

Nitric oxide （NO） is involved in diverse plant growth processes; however, little is known about pathways regulating NO levels in plants. In this study, we isolated a NO-overproducing mutant of tomato （Solanum lycopersicurn） in which hyper-accumulation of NO, associated with increase in nitric oxide synthase （NOS）-Iike activity, caused diminished vegetative growth of plants and showed delayed flowering. The hyper-accumulation of NO caused drastic shortening of primary root （shr） in the seedlings, while the scavenging of NO restored root elongation in shr mutant. Inhibition of NOS- like activity reduced NO levels and stimulated root elongation in the shr mutant seedlings, while inhibition of nitrate reductase （NR） activity could not rescue shr phenotype. The stimulation of NO levels in shr mutant also conferred increased resistance to pathogen Pseudomonas syringae. Application of pharmacological inhibitors regulating ubiquitin-proteasome pathway reduced NO levels and NOS-like activity and stimulated shr root elongation. Our data indicate that a signaling pathway involving regulated protein degradation likely regulates NO synthesis in tomato.

关键词： Nitric oxide tomato nitric oxide synthase short root mutant plant development.

Profilin Regulates Apical Actin Polymerization to Control Polarized Pollen Tube Growth

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molecular plant 2015年第12期8卷 1694-1709页

作者： Xiaonan Liu Xiaolu Qu Yuxiang Jiang Ming Chang Ruihui Zhang Youjun Wu Ying Fu Shanjin Huang State Key Laboratory of plant physiology and Biochemistry College of Biological Sciences China Agricultural University Beijing 100193 China Key Laboratory of plant molecular physiology Institute of Botany Chinese Academy of Sciences Beijing 100093 China Center for plant Biology School of Life Sciences Tsinghua University Beijing 100084 China Tsinghua-Peking Joint Center for Life Sciences Beijing 100084 China National Center for plant Gene Research Beijing 100101 China present address: Department of Biological Sciences Dartmouth College Hanover NH 03755 USA

Pollen tube growth is an essential step during flowering plant reproduction, whose growth depends on a population of dynamic apical actin filaments. Apical actin filaments were thought to be involved in the regu- lation of vesicle fusion and targeting in the pollen tube. However, the molecular mechanisms that regulate the construction of apical actin structures in the pollen tube remain largely unclear. Here, we identify profilin as an important player in the regulation of actin polymerization at the apical membrane in the pollen tube. Downregulation of profilin decreased the amount of filamentous actin and induced disorganization of apical actin filaments, and reduced tip-directed vesicle transport and accumulation in the pollen tube. Direct visualization of actin dynamics revealed that the elongation of actin filaments originating at the apical membrane decreased in profilin mutant pollen tubes. Mutant profilin that is defective in binding poly-L-proline only partially rescues the actin polymerization defect in profilin mutant pollen tubes, although it fully rescues the actin turnover phenotype. We propose that profilin controls the construction of actin structures at the pollen tube tip, presumably by favoring formin-mediated actin polymerization at the apical membrane.

关键词： pollen tube actin actin polymerization profilin formin

TOM9.2 Is a Calmodulin-Binding Protein Critical for TOM Complex Assembly but Not for Mitochondrial Protein Import in Arabidopsis thaliana

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molecular plant 2017年第4期10卷 575-589页

作者： Nargis Parvin Chris Carrie Isabelle Pabst Antonia Laber Debabrata Laha Melanie V. Paul Peter Geigenberger Ralf Heermann Kirsten Jung Ute C. Vothknecht Fatima Chigri Department Biology I Botany Ludwig-Maximilians-University Munich GroBhaderner Stra6e 2-4 82152 Martinsried Germany Department Biology 1 Microbiology Ludwig-Maximilians-University Munich Grobhaderner Strabe 2-4 82152 Martinsried Germany Department of Biology Center for Integrated Protein Science (Munich) Ludwig-Maximilians-University Munich 81377 Munich Germany Center for plant molecular Biology Plant Physiology University of Tuebingen Auf der Morgenstelle 32 72076 Tuebingen Germany present address: plant Cell Biology IZMB University of Bonn Kirschallee 153115 Bonn Germany present address: Center for plant molecular Biology Developmental Genetics University of Tubingen Auf der Morgenstelle 32 72076 Tubingen Germany

The translocon on the outer membrane of mitochondria （TOM） facilitates the import of nuclear-encoded proteins. The principal machinery of mitochondrial protein transport seems conserved in eukaryotes; however, divergence in the composition and structure of TOM components has been observed between mammals, yeast, and plants. TOM9, the plant homolog of yeast Tom22, is significantly smaller due to a truncation in the cytosolic receptor domain, and its precise function is not understood. Here we provide evidence showing that TOM9.2 from Arabidopsis thaliana is involved in the formation of mature TOM com- plex, most likely by influencing the assembly of the pore-forming subunit TOM40. Dexamethasone- induced RNAi gene silencing of TOM9.2 results in a severe reduction in the mature TOM complex, and the assembly of newly imported TOM40 into the complex is impaired. Nevertheless, mutant plants are fully viable and no obvious downstream effects of the loss of TOM complex, i.e., on mitochondrial import ca- pacity, were observed. Furthermore, we found that TOM9.2 can bind calmodulin （CAM） in vitro and that CaM impairs the assembly of TOM complex in the isolated wild-type mitochondria, suggesting a regula- tory role of TOM9.2 and a possible integration of TOM assembly into the cellular calcium signaling network.

关键词： protein import plant mitochondria TOM complex calmodulin calcium signaling