Evidence for a subgroup of thioredoxin h that requires GSH/Grx for its reduction

AbstractPoplar thioredoxin h4 (popTrxh4) and a related CXXS type (popCXXS3) are both members of a plant thioredoxin h subgroup. PopTrxh4 exhibits the usual catalytic site WCGPC, whereas popCXXS3 harbors the non-typical active site WCMPS. Recombinant popTrxh4 and popCXXS3 are not reduced either by Arabidopsis thaliana NADPH-dependent thioredoxin reductases (NTR) A and B or by Escherichia coli NTR. We report here evidence that a poplar glutaredoxin as well as three E. coli Grxs are able to reduce popTrxh4. PopTrxh4 is able to reduce several thioredoxin targets as peroxiredoxins or methionine sulfoxide reductases. On the other hand, popCXXS3 exhibits an activity in the presence of glutathione and hydroxyethyldisulfide. Except for examples of glutathiolation, these are the first two examples of a direct interconnection between the thioredoxin and glutathione/glutaredoxin systems

Cysteine–based redox regulation and signaling in plants

Living organisms are subjected to oxidative stress conditions which are characterized by the production of reactive oxygen, nitrogen, and sulfur species. In plants as in other organisms, many of these compounds have a dual function as they damage different types of macromolecules but they also likely fulfil an important role as secondary messengers. Owing to the reactivity of their thiol groups, some protein cysteine residues are particularly prone to oxidation by these molecules. In the past years, besides their recognized catalytic and regulatory functions, the modification of cysteine thiol group was increasingly viewed as either protective or redox signaling mechanisms. The most physiologically relevant reversible redox post-translational modifications (PTMs) are disulfide bonds, sulfenic acids, S-glutathione adducts, S-nitrosothiols and to a lesser extent S-sulfenyl-amides, thiosulfinates and S-persulfides. These redox PTMs are mostly controlled by two oxidoreductase families, thioredoxins and glutaredoxins. This review focuses on recent advances highlighting the variety and physiological roles of these PTMs and the proteomic strategies used for their detection

Biochemical properties of poplar thioredoxin z

AbstractTrx-z is a chloroplastic thioredoxin, exhibiting a usual WCGPC active site, but whose biochemical properties are unknown. We demonstrate here that Trx-z supports the activity of several plastidial antioxidant enzymes, such as thiol-peroxidases and methionine sulfoxide reductases, using electrons provided by ferredoxin–thioredoxin reductase. Its disulfide reductase activity requires the presence of both active site cysteines forming a catalytic disulfide bridge with a midpoint redox potential of −251mV at pH7. These in vitro biochemical data suggest that, besides its decisive role in the regulation of plastidial transcription, Trx-z might also be involved in stress response

The Poplar-Poplar Rust Interaction: Insights from Genomics and Transcriptomics

Poplars are extensively cultivated worldwide, and their susceptibility to the leaf rust fungus Melampsora larici-populina leads to considerable damages in plantations. Despite a good knowledge of the poplar rust life cycle, and particularly the epidemics on poplar, the perennial status of the plant host and the obligate biotrophic lifestyle of the rust fungus are bottlenecks for molecular investigations. Following the completion of both M. larici-populina and Populus trichocarpa genome sequences, gene families involved in poplar resistance or in rust fungus virulence were investigated, allowing the identification of key genetic determinants likely controlling the outcome of the interaction. Specific expansions of resistance and defense-related genes in poplar indicate probable innovations in perennial species in relation with host-pathogen interactions. The genome of M. Larici-populina contains a strikingly high number of genes encoding small secreted proteins (SSPs) representing hundreds of candidate effectors. Transcriptome analyses of interacting partners in compatible and incompatible interactions revealed conserved set of genes involved in poplar defense reactions as well as timely regulated expression of SSP transcripts during host tissues colonisation. Ongoing functional studies of selected candidate effectors will be achieved mainly on the basis of recombinant protein purification and subsequent characterisation

The best possible lower bound for the Perron root using traces

AbstractLet A be an n×n matrix with real eigenvalues. Wolkowicz and Styan presented bounds for the eigenvalues, using only n, trA, and trA2. We show that their lower bound for the largest eigenvalue works also as a lower bound for the Perron root of A if A is nonnegative and its eigenvalues are not necessarily real. We also show that this bound is optimal under certain conditions. Finally, we solve completely the problem to find the optimal lower bound for the Perron root using only n, trA, and trA2

Occurrence, Evolution and Specificities of Iron-Sulfur Proteins and Maturation Factors in Chloroplasts from Algae

peer reviewe

Function of glutathione peroxidases in legume root nodules

© The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.[EN] Glutathione peroxidases (Gpxs) are antioxidant enzymes not studied so far in legume nodules, despite the fact that reactive oxygen species are produced at different steps of the symbiosis. The function of two Gpxs that are highly expressed in nodules of the model legume Lotus japonicus was examined. Gene expression analysis, enzymatic and nitrosylation assays, yeast cell complementation, in situ mRNA hybridization, immunoelectron microscopy, and LjGpx-green fluorescent protein (GFP) fusions were used to characterize the enzymes and to localize each transcript and isoform in nodules. The LjGpx1 and LjGpx3 genes encode thioredoxin-dependent phospholipid hydroperoxidases and are differentially regulated in response to nitric oxide (NO) and hormones. LjGpx1 and LjGpx3 are nitrosylated in vitro or in plants treated with S-nitrosoglutathione (GSNO). Consistent with the modification of the peroxidatic cysteine of LjGpx3, in vitro assays demonstrated that this modification results in enzyme inhibition. The enzymes are highly expressed in the infected zone, but the LjGpx3 mRNA is also detected in the cortex and vascular bundles. LjGpx1 is localized to the plastids and nuclei, and LjGpx3 to the cytosol and endoplasmic reticulum. Based on yeast complementation experiments, both enzymes protect against oxidative stress, salt stress, and membrane damage. It is concluded that both LjGpxs perform major antioxidative functions in nodules, preventing lipid peroxidation and other oxidative processes at different subcellular sites of vascular and infected cells. The enzymes are probably involved in hormone and NO signalling, and may be regulated through nitrosylation of the peroxidatic cysteine essential for catalytic function.AS and PBS were the recipients of predoctoral (Formacion de Personal Investigador) and postdoctoral (Marie Curie) contracts, respectively. We thank Martin Crespi for help with in situ RNA hybridization and Simon Avery for sharing the yeast mutant and for helpful advice. This work was supported by Ministerio de Economia y Competitividad-Fondo Europeo de Desarrollo Regional (AGL2011-24524 and AGL2014-53717-R). The UMR1136 is supported by a grant overseen by the French National Research Agency (ANR) as part of the 'Investissements d'Avenir' programme (ANR-11-LABX-0002-01, Lab of Excellence ARBRE). MM and KJD acknowledge support within SPP1710. The proteomic analysis was performed in the CSIC/UAB Proteomics Facility of IIBB-CSIC that belongs to ProteoRed, PRB2-ISCIII, supported by grant PT13/0001.Matamoros, MA.; Saiz Andres, A.; Peñuelas, M.; Bustos-Sanmamed, P.; Mulet Salort, JM.; Barja, MV.; Rouhier, N.... (2015). Function of glutathione peroxidases in legume root nodules. Journal of Experimental Botany. 66(10):2979-2990. https://doi.org/10.1093/jxb/erv066S297929906610Astier, J., Kulik, A., Koen, E., Besson-Bard, A., Bourque, S., Jeandroz, S., … Wendehenne, D. (2012). Protein S-nitrosylation: What’s going on in plants? Free Radical Biology and Medicine, 53(5), 1101-1110. doi:10.1016/j.freeradbiomed.2012.06.032Avery, A. M., & Avery, S. V. (2001). Saccharomyces cerevisiaeExpresses Three Phospholipid Hydroperoxide Glutathione Peroxidases. Journal of Biological Chemistry, 276(36), 33730-33735. doi:10.1074/jbc.m105672200Avsian-Kretchmer, O., Gueta-Dahan, Y., Lev-Yadun, S., Gollop, R., & Ben-Hayyim, G. (2004). 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Abscisic acid effects on activity and expression of barley (Hordeum vulgare) plastidial glucose-6-phosphate dehydrogenase

Total glucose-6-phosphate dehydrogenase (G6PDH) activity, protein abundance, and transcript levels of G6PDH isoforms were measured in response to exogenous abscisic acid (ABA) supply to barley (Hordeum vulgare cv Nure) hydroponic culture. Total G6PDH activity increased by 50% in roots treated for 12 h with exogenous 0.1 mM ABA. In roots, a considerable increase (35%) in plastidial P2-G6PDH transcript levels was observed during the first 3 h of ABA treatment. Similar protein variations were observed in immunoblotting analyses. In leaves, a 2-fold increase in total G6PDH activity was observed after ABA treatment, probably related to an increase in the mRNA level (increased by 50%) and amount of protein (increased by 85%) of P2-G6PDH. Together these results suggest that the plastidial P2-isoform plays an important role in ABA-treated barley plants

Removing Systemic Barriers to Equity, Diversity, and Inclusion: Report of the 2019 Plant Science Research Network Workshop “Inclusivity in the Plant Sciences”

A future in which scientific discoveries are valued and trusted by the general public cannot be achieved without greater inclusion and participation of diverse communities. To envision a path towards this future, in January 2019 a diverse group of researchers, educators, students, and administrators gathered to hear and share personal perspectives on equity, diversity, and inclusion (EDI) in the plant sciences. From these broad perspectives, the group developed strategies and identified tactics to facilitate and support EDI within and beyond the plant science community. The workshop leveraged scenario planning and the richness of its participants to develop recommendations aimed at promoting systemic change at the institutional level through the actions of scientific societies, universities, and individuals and through new funding models to support research and training. While these initiatives were formulated specifically for the plant science community, they can also serve as a model to advance EDI in other disciplines. The proposed actions are thematically broad, integrating into discovery, applied and translational science, requiring and embracing multidisciplinarity, and giving voice to previously unheard perspectives. We offer a vision of barrier-free access to participation in science, and a plant science community that reflects the diversity of our rapidly changing nation, and supports and invests in the training and well-being of all its members. The relevance and robustness of our recommendations has been tested by dramatic and global events since the workshop. The time to act upon them is now