Main conclusion Ubiquitin ligase VpRH2 is a negative regulator in the grape ABA pathway by inhibiting ABL1 , PYR1 and GRP2A expressions, and its promoter is inhibited by ABA treatment. Abstract In higher plants, ubiquitin ligases play key roles in various cellular processes. As in our previous study (Wang et al. in J Exp Bot 68:1669–1687, 2017), grape RING-H2-type ubiquitin ligase gene VpRH2 and its promoter was induced by powdery mildew and showed resistance to the disease. Diverse small-molecule hormones, like salicylic acid (SA), methyl jasmonate (MeJA) or abscisic acid (ABA), play pivotal roles in plant resistance. Here we found that VpRH2 expression could be induced by SA and MeJA treatment, but inhibited by ABA treatment. The promoter of VpRH2 revealed a similar variation trend under exogenous hormone treatments as the gene expression by GUS activity assay. By a series of deletion fragments, the promoter fragment of VpRH2-P656 to VpRH2-P513 was necessary in response to MeJA treatment, and the inhibition of ABA treatment to the VpRH2 promoter was independent of the ABRE motif. Over-expression of VpRH2 in Arabidopsis thaliana plants displayed ABA-insensitive phenotypes at the germination stage compared to wild type plants. In VpRH2 over-expressing Vitis vinifera cv. Thompson Seedless plants after ABA treatments, the expression of the ABA pathway related genes ABL1 and PYR1 showed a suppresive trend. Moreover, VpGRP2A (an VpRH2-interacting protein) also showed a suppresive trend in response to ABA treatment in VpRH2-overexpressing plants. Our results demonstrate that VpRH2 is a negative regulator in the grape ABA signal pathway by inhibiting ABL1 , PYR1 and GRP2A expressions, and its promoter was also inhibited by ABA treatment.

中文翻译：

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葡萄泛素连接酶 VpRH2 是响应 ABA 处理的负调节剂

主要结论 泛素连接酶 VpRH2 是葡萄 ABA 通路的负调节因子，通过抑制 ABL1、PYR1 和 GRP2A 的表达，其启动子受到 ABA 处理的抑制。摘要 在高等植物中，泛素连接酶在各种细胞过程中发挥着关键作用。正如我们之前的研究（Wang et al. in J Exp Bot 68:1669–1687, 2017），葡萄 RING-H2 型泛素连接酶基因 VpRH2 及其启动子由白粉病诱导并显示出对该病的抗性。多种小分子激素，如水杨酸 (SA)、茉莉酸甲酯 (MeJA) 或脱落酸 (ABA)，在植物抗性中起关键作用。在这里，我们发现 VpRH2 表达可以被 SA 和 MeJA 处理诱导，但被 ABA 处理抑制。VpRH2的启动子在外源激素处理下显示出与GUS活性测定的基因表达相似的变化趋势。通过一系列缺失片段，VpRH2-P656 到 VpRH2-P513 的启动子片段是响应 MeJA 处理所必需的，ABA 处理对 VpRH2 启动子的抑制与 ABRE 基序无关。与野生型植物相比，拟南芥植物中 VpRH2 的过度表达在萌发阶段表现出对 ABA 不敏感的表型。在 VpRH2 过表达 Vitis vinifera cv. Thompson无核植株经ABA处理后，ABA通路相关基因ABL1和PYR1的表达呈抑制趋势。此外，VpGRP2A（一种 VpRH2 相互作用蛋白）在 VpRH2 过表达植物中也显示出对 ABA 处理的抑制趋势。