Abstract
ABSTRACTReciprocal antagonism between the hormones salicylic acid (SA) and jasmonic acid (JA) is particularly important during infection by the bacterial pathogenPseudomonas syringae.P. syringaesecretion of the virulence-promoting toxin, coronatine, is thought to suppress SA-induced immune responses by manipulating host JA signalling. Here, we report an unexpected JA-independent role of coronatine in promoting pathogen virulence. While JA induced resistance toP. syringae, coronatine promoted pathogen virulence by suppressing cellular accumulation of glutathione, a vital antioxidant required for immunity. Coronatine-mediated suppression of glutathione levels prevented activation of NPR1, a redox-sensitive master regulator of SA-responsive immune genes. Moreover, the accrual of nitric oxide (NO) restored virulence of coronatine-deficientP. syringae, but was counteracted by expression of the hostS-nitrosothiol reductase, Thioredoxinh5. Thus, our findings indicateP. syringaeutilises coronatine to suppresses host immunity by precisely manipulating glutathione- and NO-mediated redox signalling networks.
Publisher
Cold Spring Harbor Laboratory