Research Core for Interdisciplinary Sciences, Okayama University, Kita-ku, Okayama 700-8530, Japan.
Plant Cell. 2012 Sep;24(9):3795-804. doi: 10.1105/tpc.112.098343. Epub 2012 Sep 7.
Plant activators are compounds, such as analogs of the defense hormone salicylic acid (SA), that protect plants from pathogens by activating the plant immune system. Although some plant activators have been widely used in agriculture, the molecular mechanisms of immune induction are largely unknown. Using a newly established high-throughput screening procedure that screens for compounds that specifically potentiate pathogen-activated cell death in Arabidopsis thaliana cultured suspension cells, we identified five compounds that prime the immune response. These compounds enhanced disease resistance against pathogenic Pseudomonas bacteria in Arabidopsis plants. Pretreatments increased the accumulation of endogenous SA, but reduced its metabolite, SA-O-β-d-glucoside. Inducing compounds inhibited two SA glucosyltransferases (SAGTs) in vitro. Double knockout plants that lack both SAGTs consistently exhibited enhanced disease resistance. Our results demonstrate that manipulation of the active free SA pool via SA-inactivating enzymes can be a useful strategy for fortifying plant disease resistance and may identify useful crop protectants.
植物激活剂是通过激活植物免疫系统来保护植物免受病原体侵害的化合物，如防御激素水杨酸（SA）的类似物。虽然一些植物激活剂已被广泛应用于农业，但免疫诱导的分子机制在很大程度上尚不清楚。本研究使用新建立的高通量筛选程序，筛选能够特异性增强拟南芥培养悬浮细胞中病原体激活细胞死亡的化合物，鉴定出五种能够引发免疫反应的化合物。这些化合物增强了拟南芥植物对致病性假单胞菌的抗病性。预处理增加了内源性 SA 的积累，但减少了其代谢物 SA-O-β-d-葡萄糖苷。诱导化合物在体外抑制了两种 SA 葡糖苷酶（SAGTs）。缺乏两种 SAGTs 的双敲除植物表现出一致的增强的抗病性。我们的结果表明，通过 SA 失活酶来操纵活性游离 SA 池可以是增强植物抗病性的一种有用策略，并可能鉴定出有用的作物保护剂。
