Tomato SlERF.A1, SlERF.B4, SlERF.C3 and SlERF.A3, Members of B3 Group of ERF Family, Are Required for Resistance to Botrytis cinerea.

Zhigang Ouyang,Lihong Huang,Fengming Song,Xiaohui Li,Dayong Li,Lei Huang,Shixia Liu,Yafen Zhang,Yongbo Hong,Huijuan Zhang

doi:10.3389/fpls.2016.01964

Abstract

The Ethylene-Responsive Factors (ERFs) comprise a large family of transcriptional factors that play critical roles in plant immunity. Gray mold disease caused by Botrytis cinerea, a typical necrotrophic fungal pathogen, is the serious disease that threatens tomato production worldwide. However, littler is known about the molecular mechanism regulating the immunity to B. cinerea in tomato. In the present study, virus-induced gene silencing (VIGS)-based functional analyses of 18 members of B3 group (also called Group IX) in tomato ERF family were performed to identify putative ERFs that are involved in disease resistance against B. cinerea. VIGS-based silencing of either SlERF.B1 or SlERF.C2 had lethal effect while silencing of SlERF.A3 (Pit4) significantly suppressed vegetative growth of tomato plants. Importantly, silencing of SlERF.A1, SlERF.A3, SlERF.B4, or SlERF.C3 resulted in increased susceptibility to B. cinerea, attenuated the B. cinerea-induced expression of jasmonic acid/ethylene-mediated signaling responsive defense genes and promoted the B. cinerea-induced H2O2 accumulation. However, silencing of SlERF.A3 also decreased the resistance against Pseudomonas syringae pv. tomato (Pst) DC3000 but silencing of SlERF.A1, SlERF.B4 or SlERF.C3 did not affect the resistance to this bacterial pathogen. Expression of SlERF.A1, SlERF.A3, SlERF.B4, or SlERF.C3 was induced by B. cinerea and by defense signaling hormones such as salicylic acid, methyl jasmonate, and 1-aminocyclopropane-1-carboxylic acid (an ethylene precursor). SlERF.A1, SlERF.B4, SlERF.C3, and SlERF.A3 proteins were found to localize in nucleus of cells and possess transactivation activity in yeasts. These data suggest that SlERF.A1, SlERF.B4, and SlERF.C3, three previously uncharacterized ERFs in B3 group, and SlERF.A3, a previously identified ERF with function in immunity to Pst DC3000, play important roles in resistance against B. cinerea in tomato.

Highlights

During last decade, extensive genetics and molecular studies revealed that higher plants have evolved to possess a sophisticated innate immunity system, which is similar to the innate immunity in animals (Dodds and Rathjen, 2010; Fu and Dong, 2013)
The B3 Group of the Tomato Ethylene-Responsive Factors (ERFs) Family and virus-induced gene silencing (VIGS)-based Silencing of the Selected B3 Group ERF Genes
Locus Solyc09g089910 corresponding to SlERF59 (Sharma et al, 2010) was not included as a B3 group member (Pirrello et al, 2012; Liu et al, 2016)

Summary

Introduction

Extensive genetics and molecular studies revealed that higher plants have evolved to possess a sophisticated innate immunity system, which is similar to the innate immunity in animals (Dodds and Rathjen, 2010; Fu and Dong, 2013). Tomato ERFs in Botrytis Resistance (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI), which are precisely regulated upon infection from different types of pathogens (Bernoux et al, 2011; Segonzac and Zipfel, 2011). Both of PTI and ETI are required for resistance to biotrophic and hemibiotrophic pathogens while only PTI is believed to be active resistance response against necrotrophic pathogens (Mengiste, 2012). Many TFs belonging to the AP2/ERF, NAC, MYB, WRKY, and bZIP (super)families have been identified to play important roles in regulating plant immune response against diverse pathogens (Eulgem and Somssich, 2007; Alves et al, 2013; Licausi et al, 2013; Nuruzzaman et al, 2013)

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Conclusion