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The NBS-LRR proteins encoded by the majority of R genes represent important intracellular receptors that directly or indirectly recognize pathogen effector proteins, which subsequently activate plant defense responses. In this study, a novel Plasmopara viticola-induced TIR-NBS-LRR gene, named VaRGA1, was cloned from leaf tissues of a highly downy mildew-resistant Vitis amurensis 'Shuanghong' grapevine. The fluorescence signal of the VaRGA1-GFP fusion protein was clearly partitioned to the cytoplasm and nucleus. The expression of the VaRGA1 gene was strongly induced during early stages of infection by P. viticola, and was also significantly upregulated after drought and salt treatments. Accordingly, grapevine leaves transiently expressing the VaRGA1 gene manifested increased resistance to P. viticola, and the overexpression of the VaRGA1 gene in Nicotiana benthamiana conferred enhanced resistance to Phytophthora parasitica through the activation of salicylic acid (SA) signaling and phenylpropanoid pathways and could also increase tolerance to drought and salt stresses at the germination and vegetable growth stages. These findings indicate that the grapevine VaRGA1 gene may function as the immune and non-immune receptors against biotic and abiotic stresses and that there may be signaling overlap between biotic and abiotic responses. [ABSTRACT FROM AUTHOR]

Downy mildew is a highly destructive disease in grapevine production. A gene encoding pathogenesis-related (PR) thaumatin-like protein was isolated from the downy mildew-resistant grapevine 'Zuoshan-1,' a clonal selection from wild Vitis amurensis Rupr. The predicted thaumatin-like protein (VaTLP) has 225 amino acids and it is acidic, with a calculated isoelectric point of 4.8. The full length of the VaTLP gene was transformed into somatic embryogenic calli of V. vinifera 'Thompson Seedless' via Agrobacterium tumefaciens. Real-time RT-PCR confirmed that the VaTLP gene was expressed at a high level in the transgenic grapevines. Improved resistance of the transgenic lines against downy mildew was evaluated using leaf disks and whole plants inoculated with Plasmopara viticola, the pathogen causing grapevine downy mildew disease. Bioassay of the pathogen showed that both hyphae growth and asexual reproduction were inhibited significantly among the transgenic plants. Histological analysis also confirmed this disease resistance by demonstrating the inhibition and malformation of hyphae development in leaf tissue of the transgenic plants. These results indicated that the accumulation of VaTLP could enhance resistance to P. viticola in transgenic 'Thompson Seedless' grapevines. [ABSTRACT FROM AUTHOR]