Capsicum annuumWRKY protein CaWRKY1 is a negative regulator of pathogen defense

Abstract

Summary• Plants respond to pathogens by regulating a network of signaling pathways that fine-tune transcriptional activation of defense-related genes.• The aim of this study was to determine the role of Capsicum annuum WRKY zinc finger-domain transcription factor 1 (CaWRKY1) in defense. In previous studies, CaWRKY1 was found to be rapidly induced in C. annuum (chili pepper) leaves by incompatible and compatible pathogen inoculations, but the complexity of the network of the WRKY family prevented the function of CaWRKY1 in defense from being elucidated.• Virus-induced gene silencing of CaWRKY1 in chili pepper leaves resulted in decreased growth of Xanthomonas axonopodis pv. vesicatoria race 1. CaWRKY1-overexpressing transgenic plants showed accelerated hypersensitive cell death in response to infection with tobacco mosaic virus and Pseudomonas syringe pv. tabaci. Lower levels of pathogenesis-related gene induction were observed in CaWRKY1-overexpressing transgenic plants following salicylic acid (SA) treatments.• This work suggests that the newly characterized CaWRKY1, which is strongly induced by pathogen infections and the signal molecule SA, acts as a regulator to turn off systemic acquired resistance once the pathogen challenge has diminished and to prevent spurious activation of defense responses at suboptimal concentrations of SA.

R proteins as fundamentals of plant innate immunity

“…The additional evidence was the discovery of interactions of R proteins with WRKY transcription factors or other proteins with the WRKY-like activity domains [68,69]. WRKY transcription factors such as CaWRKY in Capsicum annuum and WRKY11 and WRKY17 in A. thaliana can act as the negative regulators of resistance-related gene expression [105,106]. Overexpression of CaWRKY1 in transgenic tobacco plants results in increased susceptibility to pathogens, and its silencing in chili pepper shows the opposite effect, causing increased resistance [106].…”

“…WRKY transcription factors such as CaWRKY in Capsicum annuum and WRKY11 and WRKY17 in A. thaliana can act as the negative regulators of resistance-related gene expression [105,106]. Overexpression of CaWRKY1 in transgenic tobacco plants results in increased susceptibility to pathogens, and its silencing in chili pepper shows the opposite effect, causing increased resistance [106]. Different transcription factors play a role as inductors of the resistance response, e.g.…”

The Role of WRKY Transcription Factors in Plant Immunity

“…Overexpression of grapevine (Vitis vinifera) VvWRKY1 in tobacco (Nicotiana tabacum) rendered plants susceptible toward a variety of fungi , whereas ectopic expression of grapevine VvWRKY2 resulted in enhanced resistance to the necrotrophic fungi Alternaria tenuis, B. cinerea, and Pythium . Similarly, CaWRKY1 from chili pepper (Capsicum annuum) appears to act as a negative regulator of defense, as virus-induced gene silencing of this gene decreased growth of Xanthomonas, whereas its overexpression resulted in enhanced hypersensitive cell death to P. syringae and Tobacco mosaic virus (Oh et al, 2008). In barley (Hordeum vulgare), MLA confers isolate-specific resistance to the powdery mildew Blumeria graminis.…”

Morphological Classification of Trichomes Associated with Possible Biotic Stress Resistance in the Genus Capsicum

“…Chili pepper is one of the most important vegetable crop in the world, and quite a few studies were undertaken in molecular biology, genetics and breeding (Kim et al, 2010;Yoon et al, 2009;Yeom et al, 2011;Oh et al, 2008). Because of the association of trichome-forming phenotype with multiple biotic stress resistances, studies on genetic analysis of trichome-formation in pepper plants were performed (Kim et al, 2010).…”