The Effects of Destruxin A on Relish and Rel Gene Regulation to the Suspected Immune-Related Genes of Silkworm

Destruxin A (DA), a cyclodepsipeptidic mycotoxin of entomopathogenic fungus, , has anti-immunity activity against insects, but the mechanism of immune regulation is not clear yet. In our previous experiment, the significant expression changes of , , and genes in a silkworm's hemocytes were found, which suggested that these genes might be involved in insect's innate immunity. In the current experiment, the silkworm cell line Bm12 was used to survey the expression levels of these genes after the cells were treated with DA and the transcription factors , and were silenced by specific siRNA. The results indicated that, after the cells were treated by DA, the gene expression level of was significantly downregulated, but and were not changed. The results also showed that the gene expression levels of and had similar phenomena, i.e., downregulation with individual gene silence or DA treatment, upregulation with combination of gene silence and DA treatment, upregulation with individual gene silence, and downregulation with combination of gene silence plus DA treatment, but no changes in the gene silence combined with DA treatment. For the gene, the downregulated expressions were found in individual gene silence or DA treatment, upregulation in the combination treatment of gene silence plus DA, and the individual treatment of or silence. It is suggested that expressions of the and genes are closely related to the Imd signal pathway, but genes might involve in both Toll and Imd pathways. Furthermore, the gene acts as an activator and the gene acts as a repressor for both and gene expressions. It also implies that DA may participate in the splicing process of where was promoted. Our research will provide new insights on the understanding of the activity mechanisms of destruxins.