The Key Laboratory of Plant Development and Environment Adaptation Biology, Ministry of Education, School of Life Science, Shandong University, Qingdao 266237, China.
The Key Laboratory of Plant Development and Environment Adaptation Biology, Ministry of Education, School of Life Science, Shandong University, Qingdao 266237, China
Plant Physiol. 2019 Aug;180(4):2167-2181. doi: 10.1104/pp.19.00091. Epub 2019 Apr 8.
Plant systemic acquired resistance (SAR) provides an efficient broad-spectrum immune response to pathogens. SAR involves mobile signal molecules that are generated by infected tissues and transported to systemic tissues. Methyl salicylate (MeSA), a molecule that can be converted to salicylic acid (SA), is an essential signal for establishing SAR, particularly under a short period of exposure to light after pathogen infection. Thus, the control of MeSA homeostasis is important for an optimal SAR response. Here, we characterized a uridine diphosphate-glycosyltransferase, UGT71C3, in Arabidopsis (), which was induced mainly in leaf tissue by pathogens including DC3000/ ( pv tomato strain DC3000 expressing avrRpt2). Biochemical analysis indicated that UGT71C3 exhibited strong enzymatic activity toward MeSA to form MeSA glucosides in vitro and in vivo. After primary pathogen infection by DC3000/, knockout mutants exhibited more powerful systemic resistance to secondary pathogen infection than that of wild-type plants, whereas systemic resistance in overexpression lines was compromised. In agreement, after primary infection of local leaves, knockout mutants accumulated significantly more systemic MeSA and SA than that in wild-type plants. whereas overexpression lines accumulated less. Our results suggest that MeSA glucosylation by UGT71C3 facilitates negative regulation of the SAR response by modulating homeostasis of MeSA and SA. This study unveils further SAR regulation mechanisms and highlights the role of glucosylation of MeSA and potentially other systemic signals in negatively modulating plant systemic defense.
植物系统获得性抗性 (SAR) 为病原体提供了有效的广谱免疫反应。SAR 涉及由感染组织产生并运输到全身组织的移动信号分子。水杨酸甲酯 (MeSA) 是一种可以转化为水杨酸 (SA) 的分子，是建立 SAR 的必需信号，尤其是在病原体感染后短暂暴露于光线下时。因此，MeSA 动态平衡的控制对于最佳 SAR 反应很重要。在这里，我们在拟南芥中鉴定了一个尿苷二磷酸-糖基转移酶 UGT71C3（），该基因主要受病原体诱导，包括 DC3000/（表达 avrRpt2 的 pv tomato 菌株 DC3000）。生化分析表明，UGT71C3 对 MeSA 表现出强烈的酶活性，能够在体外和体内将 MeSA 形成 MeSA 糖苷。在 primary pathogen 感染 DC3000/后， knockout 突变体比野生型植物表现出更强的系统抗性 secondary pathogen 感染，而 overexpression 系则受到损害。一致的是，在局部叶片 primary infection 后， knockout 突变体比野生型植物积累了更多的系统 MeSA 和 SA，而 overexpression 系则积累较少。我们的结果表明，UGT71C3 将 MeSA 葡糖苷化有助于通过调节 MeSA 和 SA 的动态平衡来负调控 SAR 反应。这项研究揭示了进一步的 SAR 调节机制，并强调了 MeSA 葡糖苷化和可能其他系统信号在负调控植物系统防御中的作用。
