壳寡糖诱导的苎麻抗夜蛾分子机制

The ramie moth (Cocytodes coerulea) is one of the most important foliar insects of ramie, which resulted in about 20% fiber and 50% byproducts yield loss of ramie annually. Our previous studies showed that chitosan oligosaccharide (COS) can significantly induce the resistance of ramie to the ramie moth. Additionally, we have screened genes regulated by ramie moth feeding by using high throughput sequencing. However, the induced resistance mechanism of ramie to insect by COS is unclear. In this project, a middle resistant variation of ramie (cv. Chuanzhu No.8) will be induced by COS, The physiological and biochemical mechanisms will be analyzed by measuring enzyme activities and biochemical substances in the ramie leaves. According to analyze its molecular mechanism, differentially expressed genes (DEGs) will be screened by high throughput sequencing. Candidate insect resistance genes will be detected by comparing data of COS- and moth-induced DEGs. Time-course expression profiles of the candidate genes related to insect resistance genes induced by COS, ramie moth and exogenous hormone will then be represented by qRT-PCR. The signal pathways and regulation network will also be analyzed. These results will not only reveal mechanism of COS induced insect resistance of ramie, but also provide theory basis for applications of COS in pest control.

苎麻夜蛾是苎麻生产上主要的叶面害虫之一，每年导致至少20%的纤维产量及50%以上的副产物损失。申请人前期研究发现壳寡糖能显著提高苎麻抗苎麻夜蛾能力，并利用高通量测序筛选了苎麻叶片中受夜蛾取食诱导调控的基因。然而，壳寡糖诱导苎麻抗夜蛾的分子机制尚不明确。为此，本项目拟以中抗苎麻夜蛾材料川苎8号为研究对象，经壳寡糖诱导处理，通过测定诱导后苎麻叶片中与抗虫相关酶活力和防御相关生化物质的变化，分析其诱导生理生化机制；利用高通量测序技术、以未诱导样品和诱导样品全转录组信息分析差异表达基因特征和网络，结合苎麻夜蛾诱导苎麻转录组信息，筛选出候选抗虫基因，借助qRT-PCR技术分析候选基因在壳寡糖诱导过程中转录水平的差异，通过与外源激素比较，获得潜在抗虫基因可能参与的信号通路，从而阐明壳寡糖诱导的苎麻抗夜蛾的分子机制。项目研究结果将进一步完善壳寡糖诱导的抗虫机制、为壳寡糖在诱导苎麻抗虫应用上提供理论依据。

苎麻夜蛾是苎麻生产上主要的叶面害虫之一，每年导致至少20%的纤维产量及50%以上的副产物损失。本项目以中抗苎麻夜蛾材料川苎8号为研究对象，经壳寡糖诱导处理，通过测定了诱导后苎麻叶片中与抗虫相关酶活力和防御相关生化物质的变化，结果表明3g/L壳寡糖处理后，苎麻叶片中PPO、POD、SOD活力呈现先升高后降低，其中SOD和PPO活力在第7天达到最高峰，POD在第8天达到最高峰，而CAT活力低于清水对照。苎麻叶片中化学成分含量在3g/L壳寡糖处理后总酚、单宁含量均上升，尤其是在接种苎麻夜蛾后，上升幅度更大，丙二醛和草酸含量与对照相比没有显著差异。结合苎麻夜蛾诱导苎麻转录组信息，筛选出14个候选抗虫基因，利用 qRT-PCR技术分析候选基因在壳寡糖诱导过程中转录水平的差异、通过与外源激素比较，结果表明，壳寡糖处理72h的苎麻叶片中在未接虫时，与清水对照相比，差异表达基因只有87个，接种苎麻夜蛾24h以后，与接种苎麻夜蛾的清水对照叶片中差异表达基因也只有90个，壳寡糖诱导72h后再接虫24h（T96）与壳寡糖处理72h（T72）相比，差异表达基因达到371个。而未壳寡糖处理的接虫24h（CK96）与未处理（CK72）相比，差异表达基因达到988个，表明壳寡糖诱导后，启动了苎麻叶片某些基因，从而使差异表达基因大幅度减少，但表达量明显高于未壳寡糖处理的叶片。利用数据库KEGG分析发现，壳寡糖诱导后苎麻叶片中差异表达基因参与的途径主要是水杨酸途径和茉莉酸途径。经验证，筛选的14个基因在壳寡糖诱导后其表达动态与水杨酸、茉莉酸甲酯处理后一致。本项目的结果进一步完善壳寡糖诱导的抗虫机制、为壳寡糖在诱导苎麻抗虫应用上提供了理论依据。