PtrWRKY73, a salicylic acid-inducible poplar WRKY transcription factor, is involved in disease resistance in Arabidopsis thaliana.

Yanjiao Duan,Zhengyi Ling,Abdul Karim,Yuanzhong Jiang,Yunqiu He,Shenglong Ye,Keming Luo,Siqi Yang

doi:10.1007/s00299-015-1745-5

Yanjiao Duan, Zhengyi Ling + Show 6 more

Open Access

https://doi.org/10.1007/s00299-015-1745-5

Copy DOI

Abstract

Key message A salicylic acid-inducible WRKY gene, PtrWRKY73, from Populus trichocarpa , was isolated and characterized. Overexpression of PtrWRKY73 in Arabidopsis thaliana increased resistance to biotrophic pathogens but reduced resistance against necrotrophic pathogens. WRKY transcription factors are commonly involved in plant defense responses. However, limited information is available about the roles of the WRKY genes in poplar defense. In this study, we isolated a salicylic acid (SA)-inducible WRKY gene, PtrWRKY73, from Populus trichocarpa, belonging to group I family and containing two WRKY domains, a D domain and an SP cluster. PtrWRKY73 was expressed predominantly in roots, old leaves, sprouts and stems, especially in phloem and its expression was induced in response to treatment with exogenous SA. PtrWRKY73 was localized to the nucleus of plant cells and exhibited transcriptional activation. Overexpression of PtrWRKY73 in Arabidopsis thaliana resulted in increased resistance to a virulent strain of the bacterial pathogen Pseudomonas syringae (PstDC3000), but more sensitivity to the necrotrophic fungal pathogen Botrytis cinerea. The SA-mediated defense-associated genes, such as PR1, PR2 and PAD4, were markedly up-regulated in transgenic plants overexpressing PtrWRKY73. Arabidopsis non-expressor of PR1 (NPR1) was not affected, whereas a defense-related gene PAL4 had reduced in PtrWRKY73 overexpressor plants. Together, these results indicated that PtrWRKY73 plays a positive role in plant resistance to biotrophic pathogens but a negative effect on resistance against necrotrophic pathogens.Electronic supplementary materialThe online version of this article (doi:10.1007/s00299-015-1745-5) contains supplementary material, which is available to authorized users.

Highlights

Plants are constantly challenged by a variety of microbial pathogens like fungi and bacteria
These results indicated that the expression of PtrWRKY73 could be induced by defense signals and may play an important role in plant resistance to pathogens
Some WRKY genes have been cloned and characterized, for example, misexpression of PtWRKY23 from poplar (P. tremula 9 P. alba) resulted in the phylogenetic tree indicates that the closest homologue of PtrWRKY73 in Arabidopsis is AtWRKY33 (Fig. 2b) with both being inducible by salicylic acid (SA) (Zheng et al 2006), the identity between these two proteins was only 38.40 % (Fig. 2a) and the most similar region mainly distributed at the C-terminal (Data not shown)

Summary

Introduction

Plants are constantly challenged by a variety of microbial pathogens like fungi and bacteria. Complex defense mechanisms have evolved in plants to protect themselves against the attack of pathogens. Plants rapidly activate defense responses mediated by multiple signal transduction pathways (Durrant and Dong 2004; Jones and Dangl 2006). Pathogen-induced accumulation of salicylic acid (SA) leads to a rapid increase in the levels of reactive oxygen species (ROS) Necrotrophic pathogens such as Alternaria brassicicola or Botrytis cinerea can induce defense responses characterized by jasmonic acid (JA)- and ethylene (ET)dependent signal transduction pathways (Thomma et al 1999). The JA-signaling mutants, mpk and coi, show enhanced SA accumulation and signaling (Petersen et al 2000; Kloek et al 2001), whereas blocking SA accumulation in pathogen-infected plants can improve JA signaling (Spoel et al 2003)

Methods

Results

Conclusion