The <i>Arabidopsis</i> homolog of human G3BP1 is a key regulator of stomatal and apoplastic immunity

Abstract

Mammalian Ras-GTPase-activating protein SH3-domain-binding proteins (G3BPs) are a highly conserved family of RNA-binding proteins that link kinase receptor-mediated signaling to RNA metabolism. Mammalian G3BP1 is a multifunctional protein that functions in viral immunity. Here, we show that the <i>Arabidopsis thaliana</i> homolog of human G3BP1 negatively regulates plant immunity. <i>Arabidopsis g3bp1</i> mutants showed enhanced resistance to the virulent bacterial pathogen <i>Pseudomonas syringae</i> pv. <i>tomato</i>. Pathogen resistance was mediated in <i>Atg3bp1</i> mutants by altered stomatal and apoplastic immunity. <i>Atg3bp1</i> mutants restricted pathogen entry into stomates showing insensitivity to bacterial coronatine-mediated stomatal reopening. AtG3BP1 was identified as a negative regulator of defense responses, which correlated with moderate up-regulation of salicylic acid biosynthesis and signaling without growth penalty.