Expression and functional analysis of two genes encoding transcription factors, VpWRKY1 and VpWRKY2, isolated from Chinese wild Vitis pseudoreticulata

In this study, two WRKY genes were isolated from Erysiphe necator-resistant Chinese wild Vitis pseudoreticulata W. T. Wang 'Baihe-35-1', and designated as VpWRKY1 (GenBank accession no. GQ884198) and VpWRKY2 (GenBank accession no. GU565706). Nuclear localization of the two proteins was demonstrated in onion epidermal cells, while trans-activation function was confirmed in the leaves of 'Baihe-35-1'. Expression of VpWRKY1 and VpWRKY2 was induced rapidly by salicylic acid treatment in 'Baihe-35-1'. Expression of VpWRKY1 and VpWRKY2 was also induced rapidly by E. necator infection in 11 grapevine genotypes; the maximum induction of VpWRKY1 was greater in E. necator-resistant grapevine genotypes than in susceptible ones post E. necator inoculation. Furthermore, ectopic expression of VpWRKY1 or VpWRKY2 in Arabidopsis enhanced resistance to powdery mildew Erysiphe cichoracearum, and enhanced salt tolerance of transgenic plants. VpWRKY2 also enhanced cold tolerance of transgenic plants. In addition, the two proteins were shown to regulate the expression of some defense marker genes in Arabidopsis and grapevine. The data suggest that VpWRKY1 and VpWRKY2 may underlie the resistance in transgenic grapevine to E. necator and tolerance to salt and cold stresses.