Gene

Cell biology

Biology

Cytosol

Reactive oxygen species

Receptor

Immunity

Plant Immunity

Biochemistry

Peroxidase

Pseudomonas syringae

Immunology

Redox

Arabidopsis

Organic chemistry

Immune system

Mutant

Enzyme

Chemistry

Innate immune system

Nature Plants

Rapid production of H2O2 is a hallmark of plant responses to diverse pathogens and plays a crucial role in signalling downstream of various receptors that perceive immunogenic patterns. However, mechanisms by which plants sense H2O2 to regulate immunity remain poorly understood. We show that endogenous H2O2 generated upon immune activation is sensed by the thiol peroxidase PRXIIB via oxidation at Cys51, and this is essential for stomatal immunity against Pseudomonas syringae. We further show that in immune-stimulated cells, PRXIIB conjugates via Cys51 with the type 2C protein phosphatase ABA insensitive 2 (ABI2), subsequently transducing H2O2 signal to ABI2. This oxidation dramatically sensitizes H2O2-mediated inhibition of the ABI2 phosphatase activity in vitro and is required for stomatal immunity in plants. Together, our results illustrate a redox relay, with PRXIIB as a sensor for H2O2 and ABI2 as a target protein, that mediates reactive oxygen species signalling during plant immunity. Reactive oxygen species are major regulatory molecules in diverse cellular processes. This article shows how an Arabidopsis thiol peroxidase, PRXIIB, senses endogenous H2O2 and regulates immune responses through a redox relay mechanism.

The cytosolic thiol peroxidase PRXIIB is an intracellular sensor for H2O2 that regulates plant immunity through a redox relay