S -nitrosylation of NADPH oxidase regulates cell death in plant immunity

The hypersensitive response in plants is a defence mechanism in which host cells infected by invading microbes undergo programmed cell death, triggered by the synthesis of nitric oxide (NO) and reactive oxygen intermediates (ROIs) at the site of infection. A study in Arabidopsis plants challenged with the bacterial pathogen Pseudomonas syringae has uncovered the molecular mechanisms involved in the hypersensitive response. Pathogen-triggered NO is shown to drive the formation of S-nitrothiols (SNOs) that facilitate the hypersensitve response. When SNO levels are high, a negative feedback loop limits the response through N-nitrosylation of NADPH oxidase. Hence, NO fine-tunes the production of SNOs and ROIs in plant immunity. Intriguingly, SNO formation occurs at a conserved cysteine in NADPH oxidases in plants, humans and flies, suggesting that this immune mechanism might operate in all higher eukaryotes.