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.

The Grape VlWRKY3 Gene Promotes Abiotic and Biotic Stress Tolerance in Transgenic Arabidopsis thaliana.

WRKY transcription factors are known to play important roles in plant responses to various abiotic and biotic stresses. The grape WRKY gene, WRKY3 was previously reported to respond to salt and drought stress, as well as methyl jasmonate and ethylene treatments in Vitis labrusca × V. vinifera cv. 'Kyoho.' In the current study, WRKY3 from the 'Kyoho' grape cultivar was constitutively expressed in Arabidopsis thaliana under control of the cauliflower mosaic virus 35S promoter. The 35S::VlWRKY3 transgenic A. thaliana plants showed improved salt and drought stress tolerance during the germination, seedling and the mature plant stages. Various physiological traits related to abiotic stress responses were evaluated to gain further insight into the role of VlWRKY3, and it was found that abiotic stress caused less damage to the transgenic seedlings than to the wild-type (WT) plants. VlWRKY3 over-expression also resulted in altered expression levels of abiotic stress-responsive genes. Moreover, the 35S::VlWRKY3 transgenic A. thaliana lines showed improved resistance to Golovinomyces cichoracearum, but increased susceptibility to Botrytis cinerea, compared with the WT plants. Collectively, these results indicate that VlWRKY3 plays important roles in responses to both abiotic and biotic stress, and modification of its expression may represent a strategy to enhance stress tolerance in crops.

Analysis of the grape (Vitis vinifera L.) thaumatin-like protein (TLP) gene family and demonstration that TLP29 contributes to disease resistance.

Thaumatin-like protein (TLP) is present as a large family in plants, and individual members play different roles in various responses to biotic and abiotic stresses. Here we studied the role of 33 putative grape (Vitis vinifera L.) TLP genes (VvTLP) in grape disease resistance. Heat maps analysis compared the expression profiles of 33 genes in disease resistant and susceptible grape species infected with anthracnose (Elsinoe ampelina), powdery mildew (Erysiphe necator) or Botrytis cinerea. Among these 33 genes, the expression level of TLP29 increased following the three pathogens inoculations, and its homolog from the disease resistant Chinese wild grape V. quinquangularis cv. 'Shang-24', was focused for functional studies. Over-expression of TLP29 from grape 'Shang-24' (VqTLP29) in Arabidopsis thaliana enhanced its resistance to powdery mildew and the bacterium Pseudomonas syringae pv. tomato DC3000, but decreased resistance to B. cinerea. Moreover, the stomatal closure immunity response to pathogen associated molecular patterns was strengthened in the transgenic lines. A comparison of the expression profiles of various resistance-related genes after infection with different pathogens indicated that VqTLP29 may be involved in the salicylic acid and jasmonic acid/ethylene signaling pathways.

Insights into the Mechanisms Underlying Ultraviolet-C Induced Resveratrol Metabolism in Grapevine (V. amurensis Rupr.) cv. "Tonghua-3".

Stilbene compounds belong to a family of secondary metabolites that are derived from the phenylpropanoid pathway. Production of the stilbene phytoalexin, resveratrol, in grape (Vitis spp.) berries is known to be induced by ultraviolet-C radiation (UV-C), which has numerous regulatory effects on plant physiology. While previous studies have described changes in gene expression caused by UV-C light in several plant species, such information has yet to be reported for grapevine. We investigated both the resveratrol content and gene expression responses of berries from V. amurensis cv. Tonghua-3 following UV-C treatment, to accelerate research into resveratrol metabolism. Comparative RNA-Seq profiling of UV-C treated and untreated grape berries resulted in the identification of a large number of differentially expressed genes. Gene ontology (GO) term classification and biochemical pathway analyses suggested that UV-C treatment caused changes in various cellular processes, as well as in both hormone and secondary metabolism. The data further indicate that UV-C induced increases in resveratrol may be related to the transcriptional regulation of genes involved in the production of secondary metabolites and signaling, as well as several transcription factors. We also observed that following UV-C treatment, 22 stilbene synthase (STS) genes exhibited increases in their expression levels and a VaSTS promoter drove the expression of the GUS reporter gene when expressed in tobacco. We therefore propose that UV-C induction of VaSTS expression is an important factor in promoting resveratrol accumulation. This transcriptome data set provides new insight into the response of grape berries to UV-C treatment, and suggests candidate genes, or promoter activity of related genes, that could be used in future functional and molecular biological studies of resveratrol metabolism.