Abstract
WRKY transcription factors are known to play important roles in plant responses to biotic stresses. We previously showed that the expression of the WRKY gene, VqWRKY52, from Chinese wild Vitis quinquangularis was strongly induced 24 h post inoculation with powdery mildew. In this study, we analyzed the expression levels of VqWRKY52 following treatment with the defense related hormones salicylic acid (SA) and methyl jasmonate, revealing that VqWRKY52 was strongly induced by SA but not JA. We characterized the VqWRKY52 gene, which encodes a WRKY III gene family member, and found that ectopic expression in Arabidopsis thaliana enhanced resistance to powdery mildew and Pseudomonas syringae pv. tomato DC3000, but increased susceptibility to Botrytis cinerea, compared with wild type (WT) plants. The transgenic A. thaliana lines displayed strong cell death induced by the biotrophic powdery mildew pathogen, the hemibiotrophic P. syringe pathogen and the necrotrophic pathogen B. cinerea. In addition, the relative expression levels of various defense-related genes were compared between the transgenic A. thaliana lines and WT plants following the infection by different pathogens. Collectively, the results indicated that VqWRKY52 plays essential roles in the SA dependent signal transduction pathway and that it can enhance the hypersensitive response cell death triggered by microbial pathogens.
Highlights
Grapevine (Vitis vinifera L.) is an important fruit crop that is cultivated world-wide, lots of grapevine varieties are highly susceptible to infection by a large variety of pathogens
We observed that the expression of VqWRKY52 was strongly induced by salicylic acid (SA) treatment, but not by MeJA, at 12 h post treatment, compared to the mock treatment, followed by a decrease at 24 h compared with the expression levels at 1 and 12 h (Figure 1A)
When ProVqWRKY52:GUS expressing leaves were treated with SA, high GUS activity levels were observed, while only low levels of activity were detected in MeJA treated leaves (Figure 1B)
Summary
Grapevine (Vitis vinifera L.) is an important fruit crop that is cultivated world-wide, lots of grapevine varieties are highly susceptible to infection by a large variety of pathogens. There is considerable interest in developing new cultivated grapevine varieties that are highly resistant to pathogens and that retain high quality fruit. To this end, classical crossbreeding is commonly used, but this is time consuming and the phenotypic traits of the filial generation are typically unstable, so this approach has limited potential. The use of molecular breeding to obtain new cultivated grapevine varieties is, in many ways, easier than conventional methods. Molecular breeding of disease-resistant grape varieties has, to date, been limited by the rudimentary understanding of the networks of defense related genes, and so identifying these in grape is an important objective
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