Current status of the multinational Arabidopsis community

The multinational Arabidopsis research community is highly collaborative and over the past thirty years these activities have been documented by the Multinational Arabidopsis Steering Committee (MASC). Here, we (a) highlight recent research advances made with the reference plant Arabidopsis thaliana; (b) provide summaries from recent reports submitted by MASC subcommittees, projects and resources associated with MASC and from MASC country representatives; and (c) initiate a call for ideas and foci for the “fourth decadal roadmap,” which will advise and coordinate the global activities of the Arabidopsis research community

Current status of the multinational Arabidopsis community

The multinational Arabidopsis research community is highly collaborative and over the past thirty years these activities have been documented by the Multinational Arabidopsis Steering Committee (MASC). Here, we (a) highlight recent research advances made with the reference plant Arabidopsis thaliana; (b) provide summaries from recent reports submitted by MASC subcommittees, projects and resources associated with MASC and from MASC country representatives; and (c) initiate a call for ideas and foci for the “fourth decadal roadmap,” which will advise and coordinate the global activities of the Arabidopsis research community

Strategies of ROS regulation and antioxidant defense during transition from C3 to C4 photosynthesis in the genus Flaveria under PEG-induced osmotic stress

PubMed ID: 23920414In the present study, we aimed to elucidate how strategies of reactive oxygen species (ROS) regulation and the antioxidant defense system changed during transition from C3 to C4 photosynthesis, by using the model genus Flaveria, which contains species belonging to different steps in C4 evolution. For this reason, four Flaveria species that have different carboxylation mechanisms, Flaveria robusta (C3), Flaveria anomala (C3-C4), Flaveria brownii (C4-like) and Flaveria bidentis (C4), were used. Physiological (growth, relative water content (RWC), osmotic potential), and photosynthetical parameters (stomatal conductance (gs), assimilation rate (A), electron transport rate (ETR)), antioxidant defense enzymes (superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX), glutathione reductases(GR)) and their isoenzymes, non-enzymatic antioxidant contents (ascorbate, glutathione), NADPH oxidase (NOX) activity, hydrogen peroxide (H2O2) content and lipid peroxidation levels (TBARS) were measured comparatively under polyethylene glycol (PEG 6000) induced osmotic stress. Under non-stressed conditions, there was a correlation only between CAT (decreasing), APX and GR (both increasing) and the type of carboxylation pathways through C3 to C4 in Flaveria species. However, they responded differently to PEG-induced osmotic stress in regards to antioxidant defense. The greatest increase in H2O2 and TBARS content was observed in C3 F. robusta, while the least substantial increase was detected in C4-like F. brownii and C4 F. bidentis, suggesting that oxidative stress is more effectively countered in C4-like and C4 species. This was achieved by a better induced enzymatic defense in F. bidentis (increased SOD, CAT, POX, and APX activity) and non-enzymatic antioxidants in F. brownii. As a response to PEG-induced oxidative stress, changes in activities of isoenzymes and also isoenzymatic patterns were observed in all Flaveria species, which might be related to ROS produced in different compartments of cells. © 2013 Elsevier GmbH.2011/BİL/009 TBAG 110T289We would like to thank Prof. Dr. Rowan Sage (University of Toronto), Prof. Dr. Peter Westhoff (Heinrich Heine University Düsseldorf) and Assist. Prof. Dr. Ferit Kocacinar (Kahramanmaras Sutcu Imam University) for providing seeds of Flaveria species. This work was support by TUBITAK ( TBAG 110T289 ) and Ege University Research Foundation ( 2011/BİL/009 ). Appendix A -

The effects of induced production of reactive oxygen species in organelles on endoplasmic reticulum stress and on the unfolded protein response in arabidopsis

PubMed ID: 26070642Background and Aims Accumulation of unfolded proteins caused by inefficient chaperone activity in the endoplasmic reticulum (ER) is termed 'ER stress', and it is perceived by a complex gene network. Induction of these genes triggers a response termed the 'unfolded protein response' (UPR). If a cell cannot overcome the accumulation of unfolded proteins, the ER-associated degradation (ERAD) system is induced to degrade those proteins. In addition to other factors, reactive oxygen species (ROS) are also produced during oxidative protein-folding in the ER. It has been shown in animal systems that there is a tight association between mitochondrial ROS and ER stress. However, in plants there are no reports concerning how induced ROS production in mitochondria and chloroplasts affects ER stress and if there is a possible role of organelle-originated ROS as a messenger molecule in the unfolded protein response. To address this issue, electron transport in chloroplasts and mitochondria and carnitine acetyl transferase (CAT) activity in peroxisomes were inhibited in wild-type Arabidopsis thaliana to induce ROS production. Expression of UPR genes was then investigated. Methods Plants of A. thaliana ecotype Col-0 were treated with various H2O2- and ROS-producing agents specific to different organelles, including the mitochondria, chloroplasts and peroxisomes. The expression of ER stress sensor/transducer genes (bZIP28, bZIP17, IRE1A, IRE1B, BiP1, BiP3), genes related to protein folding (CNX, ERO1) and ERAD genes (HRD1, SEL1, DER1, UBC32) were evaluated by qRT-PCR analysis. Key Results Relatively low concentrations of ROS were more effective for induction of the ER stress response. Mitochondrial and chloroplastic ROS production had different induction mechanisms for the UPR and ER stress responses. Conclusions Chloroplast- and mitochondria-originated ROS have distinct roles in triggering the ER stress response. In general, low concentrations of ROS induced the transcription of ER stress-related genes, which can be attributed to the roles of ROS as secondary messengers. This is the first time that ROS production in organelles has been shown to affect the ER stress response in a plant system. © 2015 The Author 2015. Published by Oxford University Press on behalf of the Annals of Botany Company

Changes in redox regulation during transition from C3 to single cell C4 photosynthesis in Bienertia sinuspersici

PubMed ID: 29128610Bienertia sinuspersici performs single cell C4 photosynthesis without Kranz anatomy. Peripheral and central cytoplasmic compartments in a single chlorenchyma cell act as mesophyll cells and bundle sheath cells. Development of this specialized mechanism is gradual during plant development. Young leaves perform C3 photosynthesis, while mature leaves have complete C4 cycle. The aim of this work was to investigate changes in redox regulation and antioxidant defence during transition from C3 to single cell C4 photosynthesis in B. sinuspersici leaves. First, we confirmed gradual development of C4 with protein blot and qRT-PCR analysis of C4 enzymes. After this activities and isoenzymes of superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR) and H2O2 and TBARS and glutathione pool and redox status (GSH/GSSG) were determined in young, developing and mature leaves during transition from C3 to single cell C4 photosynthesis. Activities of SOD, APX and POX decrease, while GR and DHAR were increased. However, most striking results were the changes in isoenzyme patterns of SOD, CAT and GR which were gradual through transition to C4 photosynthesis. © 2017 Elsevier GmbH114Z991This work was support by The Scientific and Technological Research Council of Turkey (TUBITAK) , Project no: 114Z991. -

Comparison of ROS formation and antioxidant enzymes in Cleome gynandra (C 4) and Cleome spinosa (C 3) under drought stress

PubMed ID: 22118616Differences between antioxidant responses to drought in C 3 and C 4 plants are rather scanty. Even, we are not aware of any research on comparative ROS formation and antioxidant enzymes in C 3 and C 4 species differing in carboxylation pathway of same genus which would be useful to prevent other differences in plant metabolism. With this aim, relative shoot growth rate, relative water content and osmotic potential, hydrogen peroxide (H 2O 2) content and NADPH oxidase (NOX) activity, antioxidant defence system (superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX), glutathione reductase (GR) enzymes and their isoenzymes), CAT1 mRNA level, and lipid peroxidation in seedlings of Cleome spinosa (C 3) and Cleome gynandra (C 4) species of Cleome genus exposed to drought stress for 5 and 10 day (d) were comparatively investigated. Constitutive levels of antioxidant enzymes (except SOD) were consistently higher in C. spinosa than in C. gynandra under control conditions. CAT1 gene expression in C. spinosa was correlated with CAT activity but CAT1 gene expression in C. gynandra at 10 d did not show this correlation. Drought stress caused an increase in POX, CAT, APX and GR in both species. However, SOD activity was slightly decreased in C. gynandra while it was remained unchanged or increased on 5 and 10 d of stress in C. spinosa, respectively. Parallel to results of malon dialdehyde (MDA), H 2O 2 content was also remarkably increased in C. spinosa as compared to C. gynandra under drought stress. These results suggest that in C. spinosa, antioxidant defence system was insufficient to suppress the increasing ROS production under stress condition. On the other hand, in C. gynandra, although its induction was lower as compared to C. spinosa, antioxidant system was able to cope with ROS formation under drought stress. © 2011 Elsevier Ireland Ltd.This research was supported by grant in-aid 2009-Fen-074 from Ege University Research Foundation . The authors wish to thank Dr. Julian Hibberd from University of Cambridge, U.K. for providing C. gynandra seeds and also to Assist. Prof. Dr. Ferit Kocacinar from Sutcu Imam University, Turkey for providing C. spinosa seeds. For providing Klasmann Potgrond P, we would like to thank DRT, Antalya, Turkey. We also thank Dr. Ritchie Eanes (Department of Chemistry, IYTE) for extensive proof reading of the manuscript. -