EIF2α Phosphorylation by GCN2 Is Induced in the Presence of Chitin and Plays an Important Role in Plant Defense against B. cinerea Infection.

Marta Berrocal-Lobo,René Toribio,M Mar Castellano

doi:10.3390/ijms21197335

Abstract

Translation plays an important role in plant adaptation to different abiotic and biotic stresses; however, the mechanisms involved in translational regulation during each specific response and their effect in translation are poorly understood in plants. In this work, we show that GCN2 promotes eIF2α phosphorylation upon contact with Botrytis cinerea spores, and that this phosphorylation is required for the proper establishment of plant defense against the fungus. In fact, independent gcn2 mutants display an enhanced susceptibility to B. cinerea infection, which is highlighted by an increased cell death and reduced expression of ethylene- and jasmonic-related genes in the gcn2 mutants. eIF2α phosphorylation is not only triggered in the presence of the fungus, but interestingly, is also achieved in the sole presence of the microbe-associated molecular pattern (MAMP) chitin. Moreover, analysis of de novo protein synthesis by 35SMet–35SCys incorporation indicates that chitin treatment promotes a global inhibition of translation. Taken together, these results suggest that eIF2α phosphorylation by GCN2 is promoted in the presence of chitin and plays an important role in plant defense against B. cinerea infection.

Highlights

Translation is highly regulated in plants during different developmental programs and in response to multiple stimuli [1,2,3]
GCN2-mediated eukaryotic initiation factor 2 subunit α (eIF2α)-P is induced by the presence of the whitefly Bemisia tabaci in tobacco plants [14] and in response to bacterial infection by P. syringae pv. tomato (Pst) strains DC3000 and DC3118 in Arabidopsis [16]. Despite these pieces of evidence suggesting a role of GCN2 and eIF2α phosphorylation in plant defense, it is still unclear whether eIF2α phosphorylation can play a main role in other pathogen responses and which are the molecular players involved in the activation of the GCN2 pathway
They showed a higher level of cell death on the infected leaves. These symptoms were correlated with an increased ion leakage in the gcn2 mutant lines (Figure 1B). It is well-known that ET and jasmonic acid (JA) pathways play a main role in plant defense against B. cinerea infection [17,18,19]; to determine if this higher susceptibility is reflected at the molecular level, we carried out Quantitative Real-Time PCR (qRT-PCR) analysis of ET and JA marker genes

Summary

Introduction

Translation is highly regulated in plants during different developmental programs and in response to multiple stimuli [1,2,3]. Tomato (Pst) strains DC3000 and DC3118 in Arabidopsis [16] Despite these pieces of evidence suggesting a role of GCN2 and eIF2α phosphorylation in plant defense, it is still unclear whether eIF2α phosphorylation can play a main role in other pathogen responses and which are the molecular players involved in the activation of the GCN2 pathway. This produces a gap in the knowledge on the possible effect of eIF2α in the regulation of translation during plant immunity

Results

Discussion

Pathogen Inoculation and Phenotypic Assessment

Metabolic Labeling of Newly Synthesized Proteins

Polysome Profiling