AtERF14, a member of the ERF family of transcription factors, plays a nonredundant role in plant defense.

Luis OñAte-SáNchez,Karam B Singh,Jodi Young,Jonathan P Anderson

doi:10.1104/pp.106.086637

Abstract

We had previously shown that several transcription factors of the ethylene (ET) response factor (ERF) family were induced with different but overlapping kinetics following challenge of Arabidopsis (Arabidopsis thaliana) with Pseudomonas syringae pv tomato DC3000 (avrRpt2). One of these genes, a transcriptional activator, AtERF14, was induced at the same time as ERF-target genes (ChiB, basic chitinase). To unravel the potential function of AtERF14 in regulating the plant defense response, we have analyzed gain- and loss-of-function mutants. We show here that AtERF14 has a prominent role in the plant defense response, since overexpression of AtERF14 had dramatic effects on both plant phenotype and defense gene expression and AtERF14 loss-of-function mutants showed impaired induction of defense genes following exogenous ET treatment and increased susceptibility to Fusarium oxysporum. Moreover, the expression of other ERF genes involved in defense and ET/jasmonic acid responses, such as ERF1 and AtERF2, depends on AtERF14 expression. A number of ERFs have been shown to function in the defense response through overexpression. However, the effect of loss of AtERF14 function on defense gene expression, pathogen resistance, and regulation of the expression of other ERF genes is unique thus far. These results suggest a unique role for AtERF14 in regulating the plant defense response.

Highlights

We had previously shown that several transcription factors of the ethylene (ET) response factor (ERF) family were induced with different but overlapping kinetics following challenge of Arabidopsis (Arabidopsis thaliana) with Pseudomonas syringae pv tomato DC3000
To obtain AtERF14-overexpressing plants, the coding region of AtERF14 was fused to a double 35S promoter and the construct introduced into Arabidopsis Columbia (Col)-0 plants
To further investigate the phenotype caused by overexpression of AtERF14, the number of palisade mesophyll cells was counted per millimeter of transverse sections taken through the midpoint of the leaves of wild type and ox-AtERF14 lines

Summary

Introduction

We had previously shown that several transcription factors of the ethylene (ET) response factor (ERF) family were induced with different but overlapping kinetics following challenge of Arabidopsis (Arabidopsis thaliana) with Pseudomonas syringae pv tomato DC3000 (avrRpt). Several members of the ERF gene family have been shown to be functionally involved in plant defense against pathogens, as overexpression leads to increased expression of PDF1.2, ChiB, and Thi2.1 and increased resistance to a range of pathogens, both necrotrophic and biotrophic (Berrocal-Lobo et al, 2002; Gu et al, 2002; McGrath et al, 2005). Since the ERF family in Arabidopsis contains 65 members (Feng et al, 2005; Nakano et al, 2006), many of which are regulated by the same stimuli and potentially bind the same promoter element, it may be expected that a high level of functional redundancy exists and, isolation of mutant phenotypes with knockout of a single ERF is uncommon This notion is supported by the observation that few AP2/EREBP genes have been isolated through loss-of-function mutant screens. To our knowledge, no gene of the 65 member ERF or A subfamily that is associated with pathogen defense has been isolated through a mutant screen

Methods

Results

Conclusion