SEMINAR: Glutathione: From the chloroplast to the nucleus and back

The low molecular weight thiol antioxidant, reduced glutathione (GSH) is a multifunctional metabolite in plants. GSH is an important redox gatekeeper that maintains redox homeostasis. It also participates in oxidative signalling pathways that regulate gene expression and determine the outcome of plant responses to stress. GSH is synthesised in chloroplasts, from thence is transported to all the compartments of the cell including the nucleus. Mutants lacking the chloroplast GSH transporters have a low cytosolic GSH poor and have impaired responses to pathogens. Inhibition of glutathione synthesis leads to decreases the redox potential of the cytosol and the nuclei and to marked changes in gene expression. Low GSH availability leads to failure of the apical root meristem because of an arrest of the cell cycle at G1. GSH is recruited and sequestered in the nucleus early in the cell cycle by mechanisms that remain to be identified. Interestingly, mutants in candidates for GSH binding on the nuclear pore complex show very strong repression of photosynthesis, especially under high light. This talk will consider the functions of glutathione in cellular redox homeostasis and possible roles in signalling between the chloroplast and nucleus.