《环境昆虫学报》

绿僵菌素A（DA）是由金龟子绿僵菌 Metarhizium anisopliae产生的一种环缩羧肽类次生化合物，具有抗昆虫免疫作用，但是人们对其影响免疫相关基因调控的机理缺乏了解。本实验以家蚕Bm12细胞为材料，采用RNAi技术沉默相关转录因子，结合荧光定量PCR（qPCR）技术，明确DA处理或沉默TOLL和IMD信号通路相关转录因子后抗菌肽cecropin B和gloverin 4基因表达的变化。实验发现，DA能引起抗菌肽cecropin B基因表达上调和gloverin 4基因表达下调。利用特异性siRNA分别沉默转录因子BmRelish1、BmRelish2、BmRel、BmFOXg1后，发现只有沉默转录因子BmRelish时，cecropin B和gloverin 4基因表达才下调，说明这两种抗菌肽的合成均通过IMD信号通路调控。当沉默 BmRelish1或 BmRel基因及DA处理联合作用时，cecropin B基因显著下调，说明在抑制cecropin B合成时，DA与转录因子BmRelish1或者BmRel之间存在密切的协同效应；同样，在促进gloverin 4合成时，DA与转录因子BmRelish2之间也存在着协同效应。

英文摘要:

Destruxin A (DA), a cyclodepsipeptidic mycotoxin isolated from entomopathogenic fungus, Metarhizium anisopliae, has anti-immunity activity against insects, but the mechanism of immune regulation is not clear yet. In the current experiment, by means fluorescence quantitative PCR (qPCR), the silkworm cell line Bm12 was used to survey the expression level of antimicrobial peptides cecropin B and gloverin 4 genes after the cells treated with DA or silence of transcription factors in TOLL and IMD signal pathways. The results indicated that the cecropin B gene was up-regulated and gloverin 4 gene was down-regulated after the DA treatment. Respectively silencing transcription factors BmRelish1, BmRelish2, BmRel, BmFOXg1 with specific siRNA, found that after only the transcription factors BmRelish2 gene was silenced, cecropin B and gloverin 4 genes were all down-regulated. This illustrated that the two antimicrobial peptides were biosynthesized through IMD signal pathway. Furthermore, when the silence of transcription factors BmRelish1 or BmRel genes and DA treatment were combined, cecropin B gene was significantly down-regulated, which suggested that there were some synergism between DA and transcription factors BmRelish1 or BmRel to inhibit the biosynthesis of cecropin B. Similarly, there were close synergistic relations between DA and transcription factors BmRelish2 to promote the biosynthesis of gloverin 4.

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