Thiol synthetases of legumes: immunogold localization and differential gene regulation by phytohormones

Abstract

The thiol tripeptide GSH (yGIu-Cys-GIy) is a major antioxidant and redox buffer in plants, where it also performs critical functions in ccli cycle regulation, development, sulfur transport and storage, stress response, and heavy metal detoxification. In legumes, hGSH (yGlu-Cys-bAla) may partially or completely replace GSH with presumably the same functions. The synthesis of GSH is accomplished in two sequential reactions catalyzed by yECS and GSHS, whereas the synthesis of hGSH shares the same first enzyme and then requires a specific hGSHS. A better understanding of the regulation of GSH and hGSH biosynthesis in legumes during the stress response requires a precise determination of the subcellular localization of the enzymes and a quantitative expression analysis of the genes involved. For this purpose, two types of experiments were performed. First, these proteins were immunolocalized in legumes using electron microscopy. Second, the expression pattern of the three genes was determined in the model legume Lotus japonicus following treatment with several hormones that are crucial for plant development and stress signaling.