The signaling roles of glutathione in plant disease resistance

Abstract

Early studies showed that glutathione (GSH) as an antioxidant has a role in modulating plant tolerance to biotic stresses by suppressing localized necrotic symptoms following virus infections. The role of GSH in reducing severity of pathogen-induced symptoms in plants was confirmed by employing pharmacological and transgenic approaches. However, later studies have shown that GSH also has a key role in restricting pathogen levels. In fact, it seems that GSH is a pivotal factor responsible for signaling processes related to different types of plant disease resistance, including systemic acquired resistance. The signaling role of GSH in these processes is interconnected with reactive oxygen species and salicylic acid. GSH also regulates the function of plant defense-associated transcription factors and the transcriptional coregulator NPR1 by modulating their redox state. Another layer of regulation is provided by the nitric oxide donor S-nitrosoglutathione that promotes S-nitrosylation of defense-related transcription factors and transcriptional coregulators. Importantly, the role of GSH in mediating plant disease resistance-related signaling processes is independent of its antioxidant function. Changes in GSH levels and redox state triggered during plant biotic stress are not simply passive responses to oxidative damage, since GSH status regulates important elements of cellular signaling that leads to activation of defense responses.