Characterization of a Novel Cotton Subtilase Gene GbSBT1 in Response to Extracellular Stimulations and Its Role in Verticillium Resistance.

Xingpeng Duan,Kaijing Zuo,Jin Wang,Zhidong Zhang,Xianlong Zhang

doi:10.1371/journal.pone.0153988

Abstract

Verticillium wilt is a disastrous vascular disease in plants caused by Verticillium dahliae. Verticillium pathogens secrete various disease-causing effectors in cotton. This study identified a subtilase gene GbSBT1 from Gossypium babardense and investigated the roles against V. dahliae infection. GbSBT1 gene expression is responsive to V. dahliae defense signals, jasmonic acid, and ethylene treatments. Moreover, the GbSBT1 protein is mainly localized in the cell membrane and moves into the cytoplasm following jasmonic acid and ethylene treatments. Silencing GbSBT1 gene expression through virus-induced GbSBT1 gene silencing reduced the tolerance of Pima-90 (resistant genotype), but not facilitated the infection process of V. dahliae in Coker-312 (sensitive genotype). Moreover, the ectopically expressed GbSBT1 gene enhanced the resistance of Arabidopsis to Fusarium oxysporum and V. dahliae infection and activated the expression levels of defense-related genes. Furthermore, pull-down, yeast two-hybrid assay, and BiFC analysis revealed that GbSBT1 interacts with a prohibitin (PHB)-like protein expressed in V. dahliae pathogens during infection. In summary, GbSBT1 recognizes the effector PHB protein secreted from V. dahliae and is involved in Verticillium-induced resistance in cotton.

Highlights

Verticillium wilt, a devastating disease of more than 200 crops worldwide, is typically caused by the soil-borne fungus Verticillium dahliae [1]
In Arabidopsis, AtSBT5.2 exhibits oxido-reductase activity and responds to an external biotic stimulus [10], indicating that the GbSBT1 gene may function in biotic stress response
The effector candidates have been identified in the V. dahliae genome and the functions of several effectors have been recently characterized, little is known about how the cotton plant interferes with the infection and colonization of the filamentous pathogen V. dahliae

Summary

Introduction

Verticillium wilt, a devastating disease of more than 200 crops worldwide, is typically caused by the soil-borne fungus Verticillium dahliae [1]. V. dahliae secretes various effectors to evade the guard system or destroy the innate immune system of host plants [2,3,4,5]. The V. dahliae genome encodes approximately 780 secreted proteins containing signal peptides as candidate effectors [6]. These secreted proteins, including diverse polysaccharide lyases, could cleave different forms of pectins in host plants to help Verticillium wilt-causing pathogens invade xylem vessels [3,7]. V. dahliae secretes isochorismatases (without signal peptide) that suppress.

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Results

Conclusion