Bacillus thuringiensis stains induced systemic resistance in Brassica napus L.

Bacillus thuringiensis has insecticidal activity against a variety of important agricultural pests and exhibits good bacteriostatic resistance to a variety of plant pathogens, and recentily study have shown that two strains of Bt (B88-82 and RG1-6 Strain) can induce the tomato to produce resistance to R. solanacearum. However, only the induced signal pathway has been studied, and its active substances are not reported. The aim of this study was to further explore the Bt strain that could induce plant disease resistance and study the induced activity of the Bt strain, and to study the signal pathway induced by transcriptional sequencing and fluorescence quantitative PCR. The results showed that there were 303 differentially expressed genes in rape after induction of 4F5 strain, among which 86 genes were up-regulated and 217 genes weredown-regulated. The result of 4BM1 strain induction was induced by transcriptase sequencing. There were 126 differentially expressed genes in rape. Among which 64 genes were up-regulated and 62 genes were down-regulated. The analysis of these differentialexpression genes revealed that they contained Salicylic acid pathway and Ethylene pathway-related genes, which need to be further verified. Brassica napus L were treated with Bt strain 4F5, 4BM1, and stilled water as control. B. thuringiensis inoculum, the final density was 7.5×109 cfu, was sprayed on the root of 6-week-old rapeseed plants. The same volume of distilled water (DW) treatment as control. Five days after induction, rapeseed leaves were collected. For each treatment, 3 rapeseed seedlings were used.

苏云金芽孢杆菌（Bacillus thuringiensis，Bt）对多种重要农业害虫具有杀虫活性，且对多种植物病原菌表现出良好的抑菌抗性。近期研究表明，两株Bt菌株（B88-82与RG1-6菌株）可诱导番茄产生对青枯雷尔氏菌（Ralstonia solanacearum，R. solanacearum）的抗性，但目前仅对其诱导信号通路有所研究，其活性物质尚未见报道。
本研究旨在进一步筛选可诱导植物抗病性的Bt菌株，探究其诱导抗病活性，并通过转录组测序（transcriptional sequencing）与荧光定量PCR（fluorescence quantitative PCR）解析其介导的诱导信号通路。
结果显示，经4F5菌株诱导后的油菜中存在303个差异表达基因，其中86个基因上调表达，217个基因下调表达。针对4BM1菌株诱导的样本进行转录组测序后发现，油菜中存在126个差异表达基因，其中64个基因上调表达，62个基因下调表达。对上述差异表达基因的分析表明，其包含水杨酸通路与乙烯通路相关基因，有待进一步验证。
本实验以Bt菌株4F5、4BM1及无菌蒸馏水作为对照处理甘蓝型油菜（Brassica napus L.）：将终密度为7.5×10^9 cfu的苏云金芽孢杆菌菌液喷施于6周龄油菜植株的根部，以等体积无菌蒸馏水（DW）作为空白对照。诱导处理5天后，采集油菜叶片样本；每个处理组设置3株油菜幼苗作为生物学重复。