Umemura Kenji, Satou Junji, Iwata Michiaki, Uozumi Nobuyuki, Koga Jinichiro, Kawano Tomonori, Koshiba Tomokazu, Anzai Hiroyuki, Mitomi Masaaki
Agricultural & Veterinary Research Laboratories, Meiji Seika Kaisha Ltd, Yokohama 222-8567, Japan.
Plant J. 2009 Feb;57(3):463-72. doi: 10.1111/j.1365-313X.2008.03697.x. Epub 2008 Sep 26.
Systemic acquired resistance (SAR), a natural disease response in plants, can be induced chemically. Salicylic acid (SA) acts as a key endogenous signaling molecule that mediates SAR in dicotyledonous plants. However, the role of SA in monocotyledonous plants has yet to be elucidated. In this study, the mode of action of the agrochemical protectant chemical probenazole was assessed by microarray-based determination of gene expression. Cloning and characterization of the most highly activated probenazole-responsive gene revealed that it encodes UDP-glucose:SA glucosyltransferase (OsSGT1), which catalyzes the conversion of free SA into SA O-beta-glucoside (SAG). We found that SAG accumulated in rice leaf tissue following treatment with probenazole or 2,6-dichloroisonicotinic acid. A putative OsSGT1 gene from the rice cultivar Akitakomachi was cloned and the gene product expressed in Escherichia coli was characterized, and the results suggested that probenazole-responsive OsSGT1 is involved in the production of SAG. Furthermore, RNAi-mediated silencing of the OsSGT1 gene significantly reduced the probenazole-dependent development of resistance against blast disease, further supporting the suggestion that OsSGT1 is a key mediator of development of chemically induced disease resistance. The OsSGT1 gene may contribute to the SA signaling mechanism by inducing up-regulation of SAG in rice plants.
系统获得性抗性（SAR）是植物中的一种自然病害反应，可通过化学方法诱导。水杨酸（SA）作为一种关键的内源性信号分子，介导双子叶植物中的SAR。然而，SA在单子叶植物中的作用尚未阐明。在本研究中，通过基于微阵列的基因表达测定评估了农用化学保护剂烯丙苯噻唑的作用模式。对激活程度最高的烯丙苯噻唑响应基因进行克隆和表征，结果显示其编码UDP-葡萄糖：SA葡糖基转移酶（OsSGT1），该酶催化游离SA转化为SA O-β-葡萄糖苷（SAG）。我们发现，用烯丙苯噻唑或2,6-二氯异烟酸处理后，SAG在水稻叶片组织中积累。克隆了来自水稻品种秋田小町的一个假定的OsSGT1基因，并对在大肠杆菌中表达的基因产物进行了表征，结果表明烯丙苯噻唑响应性OsSGT1参与SAG的产生。此外，RNA干扰介导的OsSGT1基因沉默显著降低了烯丙苯噻唑依赖的稻瘟病抗性发展，进一步支持了OsSGT1是化学诱导抗病性发展的关键介质这一观点。OsSGT1基因可能通过诱导水稻植株中SAG的上调而有助于SA信号传导机制。
