Iwai Takayoshi, Seo Shigemi, Mitsuhara Ichiro, Ohashi Yuko
National Institute of Agrobiological Sciences, 2-1-2 Kannondai Tsukuba, Ibaraki, 305-8602 Japan.
Plant Cell Physiol. 2007 Jul;48(7):915-24. doi: 10.1093/pcp/pcm062. Epub 2007 May 21.
Probenazole (PBZ) is the active ingredient of Oryzemate, an agrochemical which is used for the protection of rice plants from Magnaporthe grisea (blast fungus). While PBZ was reported to function upstream of salicylic acid (SA) in Arabidopsis, little is known about the mechanism of PBZ-induced resistance in rice. The role of SA in blast fungus resistance is also unclear. The recommended application period for Oryzemate is just before the Japanese rainy season, at which time rice plants in the field have reached the 8-leaf stage with adult traits. Thus, the involvement of SA in PBZ-induced resistance was studied in compatible and incompatible blast fungus-rice interactions at two developmentally different leaf morphology stages. Pre-treatment of inoculated fourth leaves of young wild-type rice plants at the 4-leaf stage with PBZ did not influence the development of whitish expanding lesions (ELs) in the susceptible interaction without the accumulation of SA and pathogenesis-related (PR) proteins. However, PBZ pre-treatment increased accumulation of SA and PR proteins in the eighth leaves of adult plants at the 8-leaf stage, resulting in the formation of hypersensitive reaction (HR) lesions (HRLs). Exogenous SA induced resistance in adult but not young plants. SA concentrations in blast fungus-inoculated young leaves were essentially the same in compatible and incompatible interactions, suggesting that PBZ-induced resistance in rice is age-dependently regulated via SA accumulation.
烯丙异噻唑（PBZ）是稻瘟灵的活性成分，稻瘟灵是一种用于保护水稻植株免受稻瘟病菌侵害的农用化学品。虽然据报道PBZ在拟南芥中作用于水杨酸（SA）的上游，但关于PBZ诱导水稻产生抗性的机制知之甚少。SA在抗稻瘟病菌方面的作用也不清楚。稻瘟灵的推荐施用时期恰好在日本雨季之前，此时田间的水稻植株已达到具有成年性状的8叶期。因此，在两个发育阶段不同的叶片形态时期，研究了SA在亲和及非亲和稻瘟病菌-水稻互作中对PBZ诱导抗性的影响。在4叶期用PBZ预处理接种的野生型水稻幼苗的第四片叶，在感病互作中不会影响白色扩展病斑（ELs）的发展，且不会积累SA和病程相关（PR）蛋白。然而，PBZ预处理会增加8叶期成年植株第八片叶中SA和PR蛋白的积累，从而导致形成过敏反应（HR）病斑（HRLs）。外源SA在成年植株而非幼苗中诱导抗性。在亲和及非亲和互作中，接种稻瘟病菌的幼苗叶片中的SA浓度基本相同，这表明PBZ诱导的水稻抗性是通过SA积累进行年龄依赖性调控的。
