Institute of Insect Sciences, Zhejiang University, Hangzhou 310029, China.
Plant J. 2009 Nov;60(4):638-48. doi: 10.1111/j.1365-313X.2009.03988.x. Epub 2009 Jul 25.
The jasmonic acid (JA) pathway plays a central role in plant defense responses against insects. Some phloem-feeding insects also induce the salicylic acid (SA) pathway, thereby suppressing the plant's JA response. These phenomena have been well studied in dicotyledonous plants, but little is known about them in monocotyledons. We cloned a chloroplast-localized type 2 13-lipoxygenase gene of rice, OsHI-LOX, whose transcripts were up-regulated in response to feeding by the rice striped stem borer (SSB) Chilo suppressalis and the rice brown planthopper (BPH) Niaparvata lugens, as well as by mechanical wounding and treatment with JA. Antisense expression of OsHI-LOX (as-lox) reduced SSB- or BPH-induced JA and trypsin protease inhibitor (TrypPI) levels, improved the larval performance of SBB as well as that of the rice leaf folder (LF) Cnaphalocrocis medinalis, and increased the damage caused by SSB and LF larvae. In contrast, BPH, a phloem-feeding herbivore, showed a preference for settling and ovipositing on WT plants, on which they consumed more and survived better than on as-lox plants. The enhanced resistance of as-lox plants to BPH infestation correlated with higher levels of BPH-induced H(2)O(2) and SA, as well as with increased hypersensitive response-like cell death. These results imply that OsHI-LOX is involved in herbivore-induced JA biosynthesis, and plays contrasting roles in controlling rice resistance to chewing and phloem-feeding herbivores. The observation that suppression of JA activity results in increased resistance to an insect indicates that revision of the generalized plant defense models in monocotyledons is required, and may help develop novel strategies to protect rice against insect pests.
茉莉酸（JA）途径在植物抵御昆虫的防御反应中起着核心作用。一些取食韧皮部的昆虫也会诱导水杨酸（SA）途径，从而抑制植物的 JA 反应。这些现象在双子叶植物中得到了很好的研究，但在单子叶植物中知之甚少。我们克隆了水稻叶绿体定位的 2 型 13-脂氧合酶基因 OsHI-LOX，其转录物在受到水稻条纹叶枯虫（SSB） Chilo suppressalis 和褐飞虱（BPH） Niaparvata lugens 的取食、机械损伤以及 JA 处理的刺激后上调。OsHI-LOX 的反义表达（as-lox）降低了 SSB 或 BPH 诱导的 JA 和胰蛋白酶抑制剂（TrypPI）水平，提高了 SSB 幼虫以及水稻卷叶螟（LF） Cnaphalocrocis medinalis 的幼虫性能，并增加了 SSB 和 LF 幼虫造成的损害。相反，BPH 是一种取食韧皮部的植食性昆虫，它更喜欢在 WT 植物上定殖和产卵，在 WT 植物上它们的取食量和存活率都高于 as-lox 植物。as-lox 植物对 BPH 侵害的增强抗性与 BPH 诱导的 H2O2 和 SA 水平升高以及类似过敏反应的细胞死亡增加有关。这些结果表明，OsHI-LOX 参与了取食诱导的 JA 生物合成，并在控制水稻对咀嚼和取食韧皮部的昆虫的抗性方面发挥了相反的作用。抑制 JA 活性会导致对昆虫的抗性增加的观察结果表明，需要对单子叶植物的一般植物防御模型进行修订，这可能有助于开发保护水稻免受虫害的新策略。
