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Molecular Plant 2014年第10期7卷 1522-1532页

作者： Haiwen Zhang Huifen Zhu Yajun Pan Yuexuan Yu Sheng Luan Legong Li College of Life Sciences Capital Normal University Beijing 100048 China Department of Plant and Microbial Biology University of California Berkeley CA 94720 USA Institute of Plant Molecular Biology School of Life Sciences Nanjing University Nanjing 210093 China

Abscisic acid （ABA） regulates numerous physiological and developmental processes in plants. Recent studies identify intracellular ABA receptors, implicating the transport of ABA across cell membranes as crucial for ABA sensing and response. Here, we report that a DTX/Multidrug and Toxic Compound Extrusion （MATE） family member in Arabidopsis.thaliana, AtDTX50, functions as an ABA efflux transporter. When expressed heterologously in both an Escherichia coli strain and Xenopus oocyte cells, AtDTX50 was found to facilitate ABA efflux. Furthermore, dtx50 mutant mesophyll cells preloaded with ABA released less ABA compared with the wild-type （WT）. The AtDTX50 gene was expressed mainly in the vascular tissues and guard ceils and its expression was strongly up-regulated by exogenous ABA. The AtDTX50：：GFP fusion protein was localized predominantly to the plasma membrane. The dtx50 mutant plants were observed to be more sensitive to ABA in growth inhibition. In addition, compared with the WT, dtx50 mutant plants were more tolerant to drought with lower stomatal conductance, consistent with its function as an ABA efflux carrier in guard cells.

关键词： hormone biology molecular transport Arabidopsis.

iNID： An Analytical Framework for Identifying Network Models for Interplays among Developmental Signaling in arabidopsis

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Molecular Plant 2014年第5期7卷 792-813页

作者： Daeseok Choi Jaemyung Choi Byeongsoo Kang Seungchul Lee Young-hyun Cho Ildoo Hwang Daehee Hwang School of Interdisciplinary Bioscience and Bioengineering POSTECH 790-784 Pohang Republic of Korea Department of Life Sciences POSTECH 790-784 Pohang Republic of Korea Department of New Biology DGIST Daegu 711-873 Republic of Korea Division of Integrative Biosciences and Biotechnologies POSTECH 790-784 Pohang Republic of Korea Center for Systems Biology of Plant Senescence and-Life History Institute for BasicScience DGIST Daegu 711-873 Republic of Korea

Integration of internal and external cues into developmental programs is indispensable for growth and development of plants, which involve complex interplays among signaling pathways activated by the internal and external factors （IEFs）. However, decoding these complex interplays is still challenging. Here, we present a web-based platform that identifies key regulators and Network models delineating Interplays among Developmental signaling （iNID） in Arabidopsis. iNID provides a comprehensive resource of （1） transcriptomes previously collected under the conditions treated with a broad spectrum of IEFs and （2） protein and genetic interactome data in Arabidopsis. In addition, iNID provides an array of tools for identifying key regulators and network models related to interplays among IEFs using transcriptome and interactome data. To demonstrate the utility of iNID, we investigated the interplays of （1） phytohormones and light and （2） phytohormones and biotic stresses. The results revealed 34 potential regulators of the interplays, some of which have not been reported in association with the interplays, and also network models that delineate the involvement of the 34 regulators in the interplays, providing novel insights into the interplays collectively defined by phytohormones, light, and biotic stresses. We then experimentally verified that BME3 and TEM1, among the selected regulators, are involved in the auxin-brassinosteroid （BR）-blue light interplay. Therefore, iNID serves as a useful tool to provide a basis for understanding interplays among IEFs.

关键词： transcriptome analysis network analysis signal interplays development Arabidopsis.

Negative Feedback Regulation of Auxin Signaling by ATHB8/ACL5-BUD2 Transcription Module

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Molecular Plant 2014年第6期7卷 1006-1025页

作者： Simona Baima Valentina Forte Marco Possenti Andres Penalosa Guido Leoni Sergio Salvi Barbara Felici Ida Ruberti Giorgio Morelli Food and Nutrition Research Centre Agricultural Research Council Via Ardeatina 546 00178 Rome Italy Present address: Department of Physics Sapienza University of Rome Rle A Moro 5 00185 Rome Italy Present address: Soil-Plant System Studies Research Centre Agricultural Research Council Via della Navicella 2-4 00184 Rome Italy Institute of Biology Molecular Medicine and NanoBiotechnology National Research Council Rle A. Moro 5 00185 Rome Italy

The role of auxin as main regulator of vascular differentiation is well established, and a direct correlation between the rate of xylem differentiation and the amount of auxin reaching the （pro）cambial cells has been proposed. It has been suggested that thermospermine produced by ACAULIS5 （ACL5） and BUSHY AND DWARF2 （BUD2） is one of the factors downstream to auxin contributing to the regulation of this process in Arabidopsis. Here, we provide an in-depth characterization of the mechanism through which ACL5 modulates xylem differentiation. We show that an increased level of ACL5 slows down xylem differentiation by negatively affecting the expression of homeodomain-leucine zipper （HD- ZIP） III and key auxin signaling genes. This mechanism involves the positive regulation of thermospermine biosynthesis by the HD-ZIP III protein Arabidopsis.THALIANA HOMEOBOX8 tightly controlling the expression of ACL5 and BUD2. In addition, we show that the HD-ZIP III protein REVOLUTA contributes to the increased leaf vascularization and long hypocotyl phenotype of acl5 likely by a direct regulation of auxin signaling genes such as LIKE AUXIN RESISTANT2 （LAX2） and LAX3. We propose that proper formation and differentiation of xylem depend on a balance between positive and negative feedback loops operating through HD-ZIP III genes.

关键词： auxin procambium thermospermine autoregulation auxin influx transporters Arabidopsis.

NTR/NRX Define a New Thioredoxin System in the Nucleus of Arabidopsis.thaliana Cells

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Molecular Plant 2014年第1期7卷 30-44页

作者： Corinne Marchal Valerie Delorme-Hinoux Laetitia Bariat Wafi Siala Christophe Belin Julio Saez-Vasquez Christophe Riondet Jean-Philippe Reichheld Universite Perpignan Via Domitia CNRS Laboratoire Genome et Developpement des Plantes UMR 5096 58 Avenue Paul Alduy-Bat T F-66860 Perpignan France Pharmacologie cellulaire et moleculaire Louvain Drug Research Institute Universite catholique de Louvain Brussels Belgium

Thioredoxins （TRX） are key components of cellular redox balance, regulating many target proteins through thiol/disulfide exchange reactions. In higher plants, TRX constitute a complex multigenic family whose members have been found in almost all cellular compartments. Although chloroplastic and cytosolic TRX systems have been largely studied, the presence of a nuclear TRX system has been elusive for a long time. Nucleoredoxins （NRX） are potential nuclear TRX found in most eukaryotic organisms. In contrast to mammals, which harbor a unique NRX, angiosperms gen- erally possess multiple NRX organized in three subfamilies. Here, we show thatArabidopsis.thaliana has two NRXgenes （AtNRX1 and AtNRX2）, respectively, belonging to subgroups I and III. While NRX1 harbors typical TRX active sites （WCG/ PPC）, NRX2 has atypical active sites （WCRPC and WCPPF）. Nevertheless, both NRXl and NRX2 have disulfide reduction capacities, although NRX1 alone can be reduced by the thioredoxin reductase NTRA. We also show that both NRX1 and NRX2 have a dual nuclear/cytosolic localization. Interestingly, we found that NTRA, previously identified as a cytosolic protein, is also partially localized in the nucleus, suggesting that a complete TRX system is functional in the nucleus. We show that NRX1 is mainly found as a dimer in vivo. nrxl and nrx2 knockout mutant plants exhibit no phenotypic perturbations under standard growth conditions. However, the nrxl mutant shows a reduced pollen fertility phenotype, suggesting a specific role of NRX1 at the haploid phase.

关键词： thioredoxin nucleoredoxin nucleus Arabidopsis.

Redox Regulation of Arabidopsis.Mitochondrial Citrate Synthase

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Molecular Plant 2014年第1期7卷 156-169页

作者： Elisabeth Schmidtmann Ann-Christine Konig Anne Orwat Dario Leister Markus Hartl Iris Finkemeier Botany Department I of Biology Ludwig-Maximilians-University Munich Grosshaderner Strasse 2 82152 Planegg-Martinsried Germany

Citrate synthase has a key role in the tricarboxylic （TCA） cycle of mitochondria of all organisms, as it cata- lyzes the first committed step which is the fusion of a carbon-carbon bond between oxaloacetate and acetyl CoA. The regulation of TCA cycle function is especially important in plants, since mitochondrial activities have to be coordinated with photosynthesis. The posttranslational regulation of TCA cycle activity in plants is thus far almost entirely unexplored. Although several TCA cycle enzymes have been identified as thioredoxin targets in vitro, the existence of any thioredoxin-dependent regulation as known for the Calvin cycle, yet remains to be demonstrated. Here we have investigated the redox regulation of the Arabidopsis.citrate synthase enzyme by site-directed mutagenesis of its six cysteine residues. Our results indicate that oxidation inhibits the enzyme activity by the formation of mixed disulfides, as the partially oxidized citrate synthase enzyme forms large redox-dependent aggregates. Furthermore, we were able to demonstrate that thioredoxin can cleave diverse intraas well as intermolecular disulfide bridges, which strongly enhances the activity of the enzyme. Activity measurements with the cysteine variants of the enzyme revealed important cysteine residues affecting total enzyme activity as well as the redox sensitivity of the enzyme.

关键词： citrate synthase mitochondria cysteine residues redox regulation thioredoxin TCA cycle Arabidopsis.

Arabidopsis.Protein Phosphatase 2C ABI1 Interacts with Type I ACC Synthases and Is Involved in the Regulation of Ozone-Induced Ethylene Biosynthesis

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Molecular Plant 2014年第6期7卷 960-976页

作者： Agnieszka Ludwikow Agata Ciesla Anna Kasprowicz-Malusk Filip Mitula Malgorzata Tajdel lukasz Gaigarnski Piotr A. Ziolkowski Piotr Kubiak Arleta Malecka Aneta Piechalak Marta Szabat Alicja Gorska Maciej Dabrowskia Izabela Ibragimow Jan Sadowski Department of Biotechnology Institute of Molecular Biology and Biotechnology Faculty of Biology Adam Mickiewicz University inPoznan Umultowska 89 61-614 Poznan Poland Institute of Plant Genetics Polish Academy of Science Strzeszynska 34 60-479 Poznan Poland Department of Molecular and Cellular Biology Institute of Molecular Biology and Biotechnology Faculty of Biology Adam MickiewiczUniversity in Poznan Umultowska 89 61-614 Poznan Poland Department of Biotechnology and Food Microbiology University of Life Sciences Wojska Polskiego 48 60-627 Poznan Poland Department of Biochemistry Institute of Molecular Bioloqy and Biotechnology Faculty of Bioloqy Adam Mickiewicz University inPoznan Umultowska 89 61-614 Poznan Poland

Ethylene plays a crucial role in various biological processes and therefore its biosynthesis is strictly regu- lated by multiple mechanisms. Posttranslational regulation, which is pivotal in controlling ethylene biosynthesis, impacts 1-aminocyclopropane 1-carboxylate synthase （ACS） protein stability via the complex interplay of specific factors. Here, we show that the Arabidopsis.thaliana protein phosphatase type 2C, ABI1, a negative regulator of abscisic acid signaling, is involved in the regulation of ethylene biosynthesis under oxidative stress conditions. We found that ABI1 interacts with ACS6 and dephosphorylates its C-terminal fragment, a target of the stress-responsive mitogen-activated protein kinase, MPK6. In addition, ABI1 controls MPK6 activity directly and by this means also affects the ACS6 phosphorylation level. Consistently with this, ozone-induced ethylene production was significantly higher in an ABI1 knockout strain （abiltd） than in wild-type plants. Importantly, an increase in stress-induced ethylene production in the abiltd mutant was compen- sated by a higher ascorbate redox state and elevated antioxidant activities. Overall, the results of this study provide evi- dence that ABI1 restricts ethylene synthesis by affecting the activity of ACS6. The ABI1 contribution to stress phenotype underpins its role in the interplay between the abscisic acid （ABA） and ethylene signaling pathways.

关键词： hormonal regulation protein phosphorylation/dephosphorylation signal transduction Arabidopsis.

How Sugars Might Coordinate Chloroplast and Nuclear Gene Expression during Acclimation to High Light Intensities

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Molecular Plant 2014年第7期7卷 1121-1137页

作者： Rainer E. Haiusler Luisa Heinrichs Jessica Schmitz Ulf-Ingo Flugge Department of Botany II Cologne Biocenter University of Cologne ZuIpicherstr. 47b 50674 Cologne Germany Present address: Plant Molecular Physiology and Biotechnology Heinrich-Heine-University Universitatsstrasse 1 40225 D~sseldorfGermany

The concept of retrograde control of nuclear gene expression assumes the generation of signals inside the chloroplasts, which are either released from or sensed inside of the organelle. In both cases, downstream signaling path- ways lead eventually to a differential regulation of nuclear gene expression and the production of proteins required in the chloroplast. This concept appears reasonable as the majority of the over 3000 predicted plastidial proteins are encoded by nuclear genes. Hence, the nucleus needs information on the status of the chloroplasts, such as during acclimation responses, which trigger massive changes in the protein composition of the thylakoid membrane and in the stroma. Here, we propose an additional control mechanism of nuclear- and plastome-encoded photosynthesis genes, taking advantage of pathways involved in sugar- or hormonal signaling. Sugars are major end products of photosynthesis and their con- tents respond very sensitively to changes in light intensities. Based on recent findings, we ask the question as to whether the carbohydrate status outside the chloroplast can be directly sensed within the chloroplast stroma. Sugars might syn- chronize the responsiveness of both genomes and thereby help to coordinate the expression of piastome- and nuclear- encoded photosynthesis genes in concert with other, more specific retrograde signals.

关键词： acclimation--physiological assimilate allocation/partitioning carbohydrate metabolism molecular physiology membrane proteins Arabidopsis.

Inositol Polyphosphate Phosphatidylinositol 5-Phosphatase9 （At5PTase9） Controls Plant Salt Tolerance by Regulating Endocytosis

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Molecular Plant 2013年第6期6卷 1781-1794页

作者： Yael Golania Yuval Kaye Omri Gilhar Mustafa Ercetin Glenda Gillaspy Alex Levine Department of Plant and Environmental Sciences The Hebrew University of Jerusalem Givat-Ram Campus Jerusalem 91904 Israel Department of Biochemistry and Fralin Biotechn01ogy Center Virginia T'ech Blacksburg VA 24061 USA

Phosphatidylinositol 5-phosphatases （5PTases） components of membrane trafficking system. Recently, we that hydrolyze the 5＇ position of the inositol ring are key reported that mutation in AtSPTase7 gene reduced produc- tion of reactive oxygen species （ROS） and decreased expression of stress-responsive genes, resulting in increased salt sensitivity. Here, we describe an even more salt-sensitive 5ptase mutant, At5ptase9, which also hydrolyzes the 5＇ phos- phate groups specifically from membrane-bound phosphatidylinositides. Interestingly, the mutants were more tolerant to osmotic stress. We analyzed the main cellular processes that may be affected by the mutation, such as production of ROS, influx of calcium, and induction of salt-response genes. The At5ptase9 mutants showed reduced ROS produc- tion and Ca2~ influx, as well as decreased fluid-phase endocytosis. Inhibition of endocytosis by phenylarsine oxide or Tyrphostin A23 in wild-type plants blocked these responses. Induction of salt-responsive genes in wild-type plants was also suppressed by the endocytosis inhibitors. Thus, inhibition of endocytosis in wild-type plants mimicked the salt stress responses, observed in the AtSptase9 mutants. In summary, our results show a key non-redundant role of At5PTase7 and 9 isozymes, and underscore the localization of membrane-bound Ptdlns in regulating plant salt tolerance by coordinating the endocytosis, ROS production, Ca2＋ influx, and induction of stress-responsive genes.

关键词： abiotic/environmental stress oxidative and photo-oxidative stress salinity protein traffic and secretion gene expression Arabidopsis.

Arabidopsis.Thylakoid Formation 1 Is a Critical Regulator for Dynamics of PSII-LHCII Complexes in Leaf Senescence and Excess Light

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Molecular Plant 2013年第5期6卷 1673-1691页

作者： Weihua Huang Qingbo Chen Ying Zhu Fenghong Hu Lingang Zhang Zhaoxue Ma Zuhua He Jirong Huang National Key Laboratory of Plant Molecular Genetics Institute of Plant Physiology and Ecology Shanghai Institutes for Biological Sciences Chinese Academy of Sciences 300 Fenglin Road Shanghai 200032 China

In higher plants, photosystem II （PSII） is a large pigment-protein supramolecular complex composed of the PSII core complex and the plant-specific peripheral light-harvesting complexes （LHCil）. PSli-LHCII complexes are highly dynamic in their quantity and macro-organization to various environmental conditions. In this study, we reported a critical factor, the Arabidopsis.Thylakoid Formation 1 （THF1） protein, which controls PSII-LHCII dynamics during dark- induced senescence and light acclimation. Loss-of-function mutations in THF1 lead to a stay-green phenotype in path- ogen-infected and senescent leaves. Both LHCII and PSll core subunits are retained in dark-induced senescent leaves of thfl, indicative of the presence of PSII-LHCII complexes. Blue native （BN）-polyacrylamide gel electrophoresis （PAGE） and immunoblot analysis showed that, in dark- and high-light-treated thfl leaves, a type of PSII-LHCII megacomplex is selec- tively retained while the stability of PSII-LHCII supercomplexes significantly decreased, suggesting a dual role of THF1 in dynamics of PSII-LHCII complexes. We showed further that THF1 interacts with Lhcb proteins in a pH-dependent manner and that the stay-green phenotype of thfl relies on the presence of LHCII complexes. Taken together, the data suggest that THF1 is required for dynamics of PSII-LHCII supramolecular organization in higher plants.

关键词： light regulation photosynthesis physiology of plant growth Arabidopsis.

Brassinosteroids Regulate the Differential Growth of Arabidopsis.Hypocotyls through Auxin Signaling Components IAA19 and ARF7

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Molecular Plant 2013年第3期6卷 887-904页

作者： Xiao-Yi Zhou Li Song Hong-Wei Xue National Key Laboratory of Plant Molecular Genetics Institute of Plant Physiology and Ecology Shanghai Institutes for Biological Sciences Chinese Academy of Sciences 300 Fenglin Road 200032 Shanghai China

Brassinosteroids （BRs） are an important class of phytohormones which regulates a wide range of physiological processes. Genetic and physiological studies have revealed that BR responses usually depend on an intact auxin signaling pathway. Here, we demonstrate that high BR concentration or enhanced BR signaling induce the differential growth of etiolated hypocotyls and result in the morphological changes, while auxin-resistant mutants, msg2 （dominant mutant of IAA19） and arf7, are insensitive to the BR effect and can partially suppress the phenotype of bzrl-D （dominant mutant of BZR1 with enhanced BR signaling）. Interestingly, BZR1 protein can directly bind to the promoter regions of both IAA19 and ARFT, indicating that IAA19 and ARF7 mediate the BR-induced differential growth by serving as direct targets of BZR1. Systemic microarray analysis revealed that a number of BR-responsive genes showed reduced BR response in msg2, confirming that BR employs auxin signaling components IAA19 and ARF7 to modulate the specific downstream processes. These results provide informative clues on the crosstalk of BR-auxin signaling and the mechanisms of BR-auxin effects in regulating differential growth.

关键词： brassinosteroids （BRs） auxin IAA19 ARF7 differential growth Arabidopsis.