紫外线对水稻抗虫能力的影响及其分子机理的研究

Ultraviolet B (UV-B) radiation and herbivore feeding are typical abiotic and biotic stresses faced by plants, respectively. UV-B can activate signaling pathways, such as jasmonate acid (JA) and at the same time, it induces secondary metabolites production. Importantly, these UV-B-induced signaling pathways and secondary metabolites usually confer resistance to herbivores. Thus UV-B may have an impact on several signaling pathways related to herbivore resistance before herbivore infestation, although little research has been done to examine this hypothesis, especially on the molecule level. In this project, we will analyze rice gene expression profiles induced by UV-B, rice striped stem borer (SSB) Chilo suppressalis infestation, and UV-B pretreatment plus SSB infestation by transcriptome to reveal the molecule mechanism underlying the priming effect of UV-B on rice resistance against SSB. Transgenic rice lines silenced in the expression of UV-B photoreceptor (UVR8) will be generated (irUVR8), and together with the irCOI1 transgenic rice that are impaired in JA signaling, they will be used to determine how UV-B changes SSB-induced phytohormone levels such as JA, protein inhibitor levels, as well as secondary metabolites levels to further understand how UV-B primes the defense of rice against SSB through the signaling pathways mediated by UVR8 and COI1. Taken together, this work will provide important insight into the role of UV-B in priming plant resistance to herbivore and the function of UVR8 and COI1 (JA signaling) in mediating UV-B-induced priming.

紫外线（UV-B）和虫害是植物面临的非生物和生物胁迫中较为典型的代表。UV-B可以激活植物茉莉酸（JA）等一系列信号途径并诱导植物产生多种次生代谢产物，而这些信号途径和次生代谢产物多与植物抗虫性相关，因此UV-B很可能在植物受昆虫危害前已影响了植物的抗虫能力，而此方面鲜有报道。我们拟利用转录组测序来分析水稻受UV-B、二化螟分别处理及UV-B预处理后加二化螟诱导前后的基因调控网络，并通过构建UV-B受体（UVR8）基因沉默水稻（irUVR8），结合JA途径受抑制的irCOI1转基因水稻，分析UV-B处理对二化螟虫咬前后JA等植物激素水平、蛋白酶抑制剂以及酚类等次生代谢产物的影响，进一步研究irUVR8和irCOI1水稻较野生型水稻对二化螟抗性的差异，以解析UVR8和COI1所调控的紫外线响应和JA信号途径在紫外线诱导植物抗虫反应中的作用，有望揭示UV-B如何影响水稻的诱导抗虫性。

为了抵御紫外线B带来的伤害，陆生植物会积累一些次生代谢产物，这些产物也可能在抵御害虫方面发挥特定功能。先前研究表明，紫外线B可以诱导多种植物对刺吸式口器昆虫的抗性反应，而紫外线B对植物抵御咀嚼式口器害虫是否及如何发挥作用，依然未知。我们研究发现紫外线B预处理拟南芥后，可以预激活茉莉酸（Jasmonic acid，JA）信号途径，拟南芥对鳞翅目害虫斜纹夜蛾（Spodoptera litura）的抗性增强。通过紫外线B受体（uvr8-2）、JA合成（dde2-2）及芥子油苷（gs4）合成突变体研究发现，紫外线B诱导的拟南芥对斜纹夜蛾的抗性依赖于茉莉酸信号途径。与之类似，紫外线B也可以增强模拟鳞翅目害虫取食诱导的烟草、水稻、玉米的茉莉酸异亮氨酸结合物（JA-isoleucine conjugate）的水平，进而增加抗虫相关化合物的积累，进而这些紫外线预处理的植物表现为更加抗虫。使用JA途径合成或感知受阻的转基因烟草和水稻确认后发现，紫外线诱导的烟草和水稻抗虫能力的增强依赖于茉莉酸信号途径。我们的研究发现了植物中较为保守的功能，即紫外线B通过茉莉酸信号途径可以诱导植物对鳞翅目害虫的抗性。