The Arabidopsis homolog of human G3BP1 is a key regulator of stomatal and apoplastic immunity.

Aala A Abulfaraj,Heribert Hirt,Salim Al-Babili,Delphine Pflieger,Ikram Blilou,Jean Bigeard,Naganand Rayapuram,Kiruthiga Mariappan,Prabhu Manickam,Xiujie Guo

doi:10.26508/lsa.201800046

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 Arabidopsis thaliana homolog of human G3BP1 negatively regulates plant immunity. Arabidopsis g3bp1 mutants showed enhanced resistance to the virulent bacterial pathogen Pseudomonas syringae pv. tomato. Pathogen resistance was mediated in Atg3bp1 mutants by altered stomatal and apoplastic immunity. Atg3bp1 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.

Highlights

RNA-binding proteins (RBPs) play a critical role in the regulation of gene expression, a feature that relies on their conformational plasticity and their capacity to interact with distinct targets (Jonas & Izaurralde, 2013; Castello et al, 2016)
Because MAMP-triggered immunity (MTI) has been reported to be associated with transcriptional reprogramming (Navarro et al, 2004; Zipfel et al, 2004), we investigated the role of AtG3BP1 in microbe-associated molecular pattern (MAMP)-triggered transcriptional responses
We report the identification of the Arabidopsis GTPase– activating protein SH3-domain–binding protein 1 (G3BP1) as an important player in salicylic acid (SA)-dependent stomatal immunity

Summary

Introduction

RNA-binding proteins (RBPs) play a critical role in the regulation of gene expression, a feature that relies on their conformational plasticity and their capacity to interact with distinct targets (Jonas & Izaurralde, 2013; Castello et al, 2016). Cells lacking G3BP1 are compromised to form SGs in response to eukaryotic initiation factor 2α phosphorylation or eIF4A inhibition but are SG competent upon heat or osmotic stress. G3BP1 is a multifunctional protein that is highly conserved in all eukaryotes, but so far, only one protein AtG3BP-like protein (At5g43960) was identified as an Arabidopsis thaliana G3BP-like protein that localizes to plant SGs and plays a role in the Arabidopsis virus resistance (Krapp et al, 2017). We identify the Arabidopsis G3BP1 homolog that belongs to a family of eight proteins and functions in plant immunity

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Results

Conclusion