The jasmonate-ZIM domain gene VqJAZ4 from the Chinese wild grape Vitis quinquangularis improves resistance to powdery mildew in Arabidopsis thaliana.

Grape (Vitis vinifera L.) is one of the most widely cultivated and economically important fruits. Most cultivated varieties of grape are highly susceptible to fungal diseases, and one of the most pervasive is powdery mildew, caused by Uncinula necator. The jasmonate-ZIM domain (JAZ) family proteins are critical for plant responses to environmental stresses. Here, we report the characterization of VqJAZ4, a jasmonate-ZIM domain gene isolated from Vitis quinquangularis, a Chinese wild Vitis species that exhibits high tolerance to several kinds of fungi. Subcellular localization assay indicated that the VqJAZ4 protein is targeted to the nucleus. The VqJAZ4 gene was strongly induced by U. necator inoculation, as well as by the defense-related hormones methyl jasmonate (MeJA) and salicylic acid (SA). The upregulation of VqJAZ4 after inoculation was dependent on its promoter sequences. Expression of VqJAZ4 in Arabidopsis thaliana improved resistance to powdery mildew. Histochemical staining assays indicated that plants expressing VqJAZ4 displayed a larger number of dead cells and stronger reactive oxygen species (ROS) burst than non-transgenic control (NTC) plants. Expression analysis of several disease-related genes suggested that VqJAZ4 expression enhanced defense responses though SA and/or JA signaling pathways. We also found that VqJAZ4-expressing Arabidopsis showed increased susceptibility to Botrytis cinerea. Taken together, these results provide evidence that VqJAZ4 may play an important role in response to fungal pathogens in grape, and may represent a candidate for future grape molecular breeding for disease resistance.