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Plant Physiology

Daria Chrobok, Simon R Law, Bastiaan Brouwer, Pernilla Lindén, Agnieszka Ziolkowska, Daniela Liebsch, Reena Narsai, Bozena Szal, Thomas Moritz, Nicolas Rouhier, James Whelan, Per Gardestrom, Olivier Keech
The functions of mitochondria during leaf senescence, a type of programmed cell death aiming at the massive retrieval of nutrients from the senescing organ to the rest of the plant, remain elusive. Here, combining experimental and analytical approaches, we showed that mitochondrial integrity is conserved until the latest stages of leaf senescence, while their number drops by 30%. Adenylate phosphorylation state assays and mitochondrial respiratory measurements indicated that the leaf energy status is also maintained during this time period...
October 15, 2016: Plant Physiology
Kengo Yokosho, Naoki Yamaji, Miho Kashino-Fujii, Jian Feng Ma
High Al tolerance of rice (Oryza sativa) is controlled by multiple tolerance genes, but the regulatory mechanisms underlying differential expression of these genes are poorly understood. Here, we investigated the factors regulating the expression of OsFRDL4, a gene encoding citrate efflux transporter involved in Al-induced citrate secretion from the roots. Analysis with chromosome segment substitution lines (CSSL) derived from Nipponbare (high OsFRDL4 expression) and Kasalath (low OsFRDL4 expression) revealed that differential expression of OsFRDL4 is responsible for the QTL for Al tolerance detected previously on chromosome 1...
October 15, 2016: Plant Physiology
Zhen Wang, Fuxing Wang, Yechun Hong, Jirong Huang, Huazhong Shi, Jian-Kang Zhu
Chloroplast as the site for photosynthesis is an essential organelle in plants, but little is known about its role in stomatal regulation and drought resistance. In this study, we show that two chloroplastic proteins essential for thylakoid formation negatively regulate drought resistance in Arabidopsis. By screening a mutant pool with T-DNA insertions in nuclear genes encoding chloroplastic proteins, we identified a HCF106 knockdown mutant exhibiting increased resistance to drought stress. The hcf106 mutant displayed elevated levels of reactive oxygen species (ROS) in guard cells, improved stomatal closure and reduced water loss under drought conditions...
October 15, 2016: Plant Physiology
Daniel Woods, Ryland Bednarek, Frédéric Bouché, Sean Gordon, John P Vogel, David F Garvin, Richard M Amasino
The transition to reproductive development is a crucial step in the plant life cycle, and the timing of this transition is an important factor in crop yields. Here, we report new insights into the genetic control of natural variation in flowering time in Brachypodium distachyon, a non-domesticated pooid grass closely related to cereals such as wheat and barley. A recombinant inbred line (RIL) population derived from a cross between the rapid-flowering accession Bd21 and the delayed-flowering accession Bd1-1 were grown in a variety of environmental conditions to enable exploration of the genetic architecture of flowering time...
October 14, 2016: Plant Physiology
Daniel Köhler, Stefan Helm, Birgit Agne, Sacha Baginsky
Toc159-containing complexes at the outer chloroplast envelope membrane form stable super-complexes with a 1-MDa translocon at the inner chloroplast envelope membrane of which Tic56 is one essential subunit. While the single mutants tic56-1 and ppi2 (toc159) have an albino phenotype and are able to grow heterotrophically, we find the double mutant to be embryo-lethal. Comprehensive quantitative proteome profiling with both single mutants in combination with GeneChip analyses identified a posttranscriptional defect in the accumulation of plastid ribosomal proteins and diminished expression of plastid encoded proteins...
October 12, 2016: Plant Physiology
Yong-Jiang Zhang, Fulton E Rockwell, Adam C Graham, Teressa Alexander, N Michele Holbrook
We report a novel form of xylem dysfunction in angiosperms: reversible collapse of the xylem conduits of the smallest vein orders that demarcate and intrusively irrigate the areoles of Quercus rubra leaves. Cryo-scanning electron microscopy revealed gradual increases in collapse from ~ -2 MPa down to ~ -3 MPa, saturating thereafter (to -4 MPa). Over this range cavitation remained negligible in these veins. Imaging of rehydration experiments showed spatially variable recovery from collapse within 20 seconds, and complete recovery after two minutes...
October 12, 2016: Plant Physiology
Birgit Piechulla, Richard Bartelt, Anne Brosemann, Uta Effmert, Harro J Bouwmeester, Frank Hippauf, Wolfgang Brandt
Flowers of Nicotiana species emit a characteristic blend including the 'cineole cassette' monoterpenes. This set of terpenes is synthesized by multiproduct enzymes, with either 1,8-cineole or α-terpineol contributing most to the volatile spectrum, thus referring to cineole or terpineol synthases (CIN, TER), respectively. To understand the molecular and structural requirements of the enzymes that favor the biochemical formation of α-terpineol and 1,8-cineole, site-directed mutagenesis, in silico modelling and semi empiric calculations were performed...
October 11, 2016: Plant Physiology
Daniel Álvarez, Björn Voss, Dirk Maass, Florian Wüst, Patrick Schaub, Peter Beyer, Ralf Welsch
Phytoene synthase (PSY) catalyzes the highly regulated, frequently rate-limiting synthesis of the first biosynthetically formed carotene. While PSY constitutes a small gene family in most plant taxa, the Brassicaceae, including Arabidopsis, predominantly possess a single PSY gene. This monogenic situation is compensated by the differential expression of two alternative splice variants (ASV) which differ in length and in the exon/intron retention of their 5'UTRs. ASV1 contains a long 5'UTR and is involved in developmentally-regulated carotenoid formation, such as during deetiolation...
October 11, 2016: Plant Physiology
Tuo Wang, Yuning Chen, Akira Tabuchi, Mei Hong, Daniel J Cosgrove
The wall-loosening actions of β-expansins are known primarily from studies of EXPB1 extracted from maize pollen. EXPB1 selectively loosens cell walls (CWs) of grasses, but its specific binding target is unknown. We characterized EXPB1 binding to sequentially extracted maize CWs, finding that the protein primarily binds glucuronoarabinoxylan (GAX), the major matrix polysaccharide in grass CWs. This binding is strongly reduced by salts, indicating that it is predominantly electrostatic in nature. For direct molecular evidence of EXPB1 binding, we conducted solid-state NMR experiments using paramagnetic relaxation enhancement (PRE), which is sensitive to distances between unpaired electrons and nuclei...
October 11, 2016: Plant Physiology
M Águila Ruiz-Sola, M Victoria Barja, David Manzano, Briardo Llorente, Bert Schipper, Jules Beekwilder, Manuel Rodriguez-Concepcion
A wide diversity of isoprenoids is produced in different plant compartments. Most groups of isoprenoids synthesized in plastids and some produced elsewhere in the plant cell derive from geranylgeranyl diphosphate (GGPP) synthesized by GGPP synthase (GGPPS) enzymes. In Arabidopsis thaliana, 5 genes appear to encode GGPPS isoforms localized in plastids (2), the endoplasmic reticulum (2), and mitochondria (1). However, the loss of function of the plastid-targeted GGPPS11 isoform (referred to as G11) is sufficient to cause lethality...
October 5, 2016: Plant Physiology
Nicole Parker, Yixing Wang, David Meinke
Natural accessions of Arabidopsis thaliana differ in their ability to tolerate a loss of chloroplast translation. These differences can be attributed in part to variation in a duplicated nuclear gene (ACC2) that targets homomeric acetyl-CoA carboxylase (ACCase) to plastids. This functional redundancy allows limited fatty acid biosynthesis to occur in the absence of heteromeric ACCase, which is encoded in part by the plastid genome. In the presence of functional ACC2, tolerant alleles of several nuclear genes, not yet identified, enhance the growth of seedlings and embryos disrupted in chloroplast translation...
October 5, 2016: Plant Physiology
David J Lea-Smith, Maite L Ortiz-Suarez, Tchern Lenn, Dennis J Nurnberg, Laura L Baers, Matthew P Davey, Lucia Parolini, Roland G Huber, Charles A R Cotton, Giulia Mastroianni, Paolo Bombelli, Petra Ungerer, Tim J Stevens, Alison G Smith, Peter J Bond, Conrad W Mullineaux, Christopher J Howe
Cyanobacteria are intricately organized, incorporating an array of internal thylakoid membranes, the site of photosynthesis, into cells no larger than other bacteria. They also synthesize C15-C19 alkanes and alkenes, which results in substantial production of hydrocarbons in the environment. All sequenced cyanobacteria encode hydrocarbon biosynthesis pathways, suggesting an important, undefined physiological role for these compounds. Here we demonstrate that hydrocarbon deficient mutants of Synechococcus sp...
October 5, 2016: Plant Physiology
Mohamed M Mira, Robert D Hill, Claudio Stasolla
Hypoxic root growth in maize is influenced by expression of phytoglobins (ZmPgbs). Relative to WT, suppression of ZmPgb1.1 or ZmPgb1.2 inhibits growth of roots exposed to 4% oxygen causing structural abnormalities in the root apical meristems. These effects were accompanied by increasing levels of reactive oxygen species (ROS), possibly through the transcriptional induction of four Respiratory Burst Oxidase Homologs (RBOHs). TUNEL-positive nuclei in meristematic cells indicated the involvement of programmed cell death (PCD) in the process...
October 4, 2016: Plant Physiology
Miwa Nagae, Martin Parniske, Masayoshi Kawaguchi, Naoya Takeda
Thiamine (vitamin B1) is essential for living organisms. Unlike animals, plants can synthesize thiamine. In Lotus japonicus, expression of two thiamine biosynthesis genes, THI1 and THIC, was enhanced by inoculation with rhizobia, but not by inoculation with arbuscular mycorrhizal fungi. THIC or THI2 (THI1 paralog) was expressed in uninoculated leaves. THI2-knockdown plants and the transposon insertion mutant thiC had chlorotic leaves. This typical phenotype of thiamine deficiency was rescued by an exogenous supply of thiamine...
October 4, 2016: Plant Physiology
Shulin Shi, Tao Wang, Ziru Chen, Zhong Tang, Zhongchang Wu, David E Salt, Dai-Yin Chao, Fangjie Zhao
Rice is a major dietary source of the toxic metalloid arsenic. Reducing its accumulation in rice grain is of critical importance to food safety. Rice roots take up arsenate and arsenite depending on the prevailing soil conditions. The first step of arsenate detoxification is its reduction to arsenite, but the enzyme(s) catalyzing this reaction in rice remains unknown. Here, we identify OsHAC1;1 and OsHAC1;2 as arsenate reductases in rice. OsHAC1;1 and OsHAC1;2 are able to complement an Escherichia coli mutant lacking the endogenous arsenate reductase and to reduce arsenate to arsenite...
October 4, 2016: Plant Physiology
Teresa Lenser, Kai Graeber, Özge Selin Cevik, Nezaket Adigüzel, Ali A Dönmez, Christopher Grosche, Marcel Kettermann, Sara Mayland-Quellhorst, Zsuzsanna Mérai, Setareh Mohammadin, Thu-Phuong Nguyen, Florian Rümpler, Christina Schulze, Katja Sperber, Tina Steinbrecher, Nils Wiegand, Miroslav Strnad, Ortrun Mittelsten Scheid, Stefan A Rensing, M Eric Schranz, Günter Theißen, Klaus Mummenhoff, Gerhard Leubner
Understanding how plants cope with changing habitats is a timely and important topic in plant research. Phenotypic plasticity describes the capability of a genotype to produce different phenotypes when exposed to different environmental conditions. In contrast, the constant production of a set of distinct phenotypes by one genotype mediates bet-hedging, a strategy that reduces the temporal variance in fitness at the expense of a lowered arithmetic mean fitness. Both phenomena are thought to represent important adaptation strategies to unstable environments...
October 4, 2016: Plant Physiology
Shweta Panchal, Reejana Chitrakar, Blaine K Thompson, Nisita Obulareddy, Debanjana Roy, W Sealy Hambright, Maeli Melotto
It has long been observed that environmental conditions play crucial roles in modulating immunity and disease in plants and animals. For instance, many bacterial plant disease outbreaks occur after periods of high humidity and rain. A critical step in bacterial infection is entry into the plant interior through wounds and natural openings, such as stomata, which are adjustable microscopic pores in the epidermal tissue. Several studies have shown that stomatal closure is an integral part of the plant immune response to reduce pathogen invasion...
October 4, 2016: Plant Physiology
Kalpana Nanjareddy, Lourdes Blanco, Manoj Kumar Arthikala, Xochitl Alvarado-Affantranger, Carmen Quinto, Federico Sanchez, Miguel Lara
The target of rapamycin (TOR) protein kinase regulates metabolism, growth and life span in yeast, animals and plants in coordination with nutrient status and environmental conditions. The nutrient-dependent nature of TOR functionality makes this kinase a putative regulator of symbiotic associations involving nutrient acquisition. However, TOR's role in these processes remains to be understood. Here, we uncovered the role of TOR during the Phaseolus vulgaris-Rhizobium symbiotic interaction. TOR was expressed in all tested Phaseolus tissues, with higher expression levels in the root meristems and senesced nodules...
October 3, 2016: Plant Physiology
Guozheng Qin, Zhu Zhu, Weihao Wang, Jianghua Cai, Yong Chen, Li Li, Shiping Tian
Fruit ripening is a complex process that involves a series of physiological and biochemical changes that ultimately influence fruit quality traits, such as color and flavor. Sugar metabolism is an important factor in ripening and there is evidence that it influences various aspects of ripening, although the associated mechanism is not well understood. In this study, we identified and analyzed the expression of 36 genes involved in sucrose metabolism in ripening tomato (Solanum lycopersicum) fruit. Chromatin immunoprecipitation and gel mobility shift assays indicated that SlVIF, which encodes a vacuolar invertase inhibitor, and SlVI, encoding a vacuolar invertase, are directly regulated by the global fruit ripening regulator RIN (RIPENING INHIBITOR)...
September 30, 2016: Plant Physiology
Rosalia Deeken, Stefanie Saupe, Jörn Klinkenberg, Michael Riedel, Jana Leide, Rainer Hedrich, Thomas Mueller
Non-specific lipid transfer proteins (nsLTPs) reversibly bind different types of lipid molecules in a hydrophobic cavity. They facilitate phospholipid transfer between membranes in vitro, play a role in cuticle and possibly in suberin formation, and might be involved in plant pathogen defense signaling. This study focuses on the role of AtLTPI-4 in crown gall development. Arabidopsis thaliana crown gall tumors, which develop upon infection with the virulent Agrobacterium tumefaciens strain C58, highly expressed the type I nsLTP gene AtLTPI-4...
September 29, 2016: Plant Physiology
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