Abstract
Glutaredoxins (GRXs) catalyse the reduction of protein disulfide bonds using glutathione as a reductant. Certain GRXs are able to transfer iron-sulfur (Fe-S) clusters to other proteins. To investigate the function of Arabidopsis thaliana GRXS17, we applied a strategy combining biochemical, genetic and physiological approaches. GRXS17 was localized in the nucleus and cytosol, and its expression was elevated in the shoot meristems and reproductive tissues. Recombinant GRXS17 bound Fe2S2 clusters, a property likely contributing to its ability to complement the defects of a yeast strain lacking the mitochondrial GRX5. However, a grxs17 knock-out Arabidopsis mutant exhibited only a minor decrease in the activities of Fe-S enzymes, suggesting that its primary function is as a disulfide oxidoreductase. The grxS17 plants were sensitive to high temperature and long-day photoperiod, resulting in elongated leaves, compromised shoot apical meristem, and delayed bolting. Both environmental conditions applied simultaneously led to a growth arrest. Using affinity chromatography and split-YFP methods, a nuclear transcriptional regulator termed NF-YC11/NC2α was identified as a GRXS17 interacting partner. A mutant deficient in NF-YC11/NC2α exhibited similar phenotypes to grxs17 in response to photoperiod. Therefore, we propose that GRXS17 interacts with NF-YC11/NC2α to relay a redox signal generated by photoperiod to maintain meristem function.
