Characterization and expression analysis of peroxiredoxin family genes from the silkworm Bombyx mori in response to phoxim and chlorpyrifos.

The organophosphorus pesticide poisoning of the silkworm Bombyx mori is one of the major events causing serious damage to sericulture. Some antioxidant enzymes play roles in regulating generation of reactive oxygen species (ROS) by pesticides including phoxim and chlorpyrifos, but relatively little is known about their effects on the silkworm peroxiredoxin family genes. Here, five peroxiredoxin (Prx) genes have been identified in silkworm genome, and Prx genes of silkworm and mammalian homologs have apparent ortholog relationship. Based on the genomic DNA sequence, putative 5'-flanking region of five BmPrxs were obtained and the transcription factor binding sites were predicted. Their expression profiles exposed to different concentrations of phoxim and chlorpyrifos for 24 h, 48 h and 72 h in midgut of silkworm were investigated using quantitative RT-PCR (qRT-PCR). The results showed that five BmPrxs and dual oxidase (BmDUOX) gene were all expressed in midgut of silkworm. After feeding with 0.375 mg/L and 0.75 mg/L phoxim, the transcription levels of BmPrx3 and BmPrx5 that can be located in mitochondria reached their peak levels at an early time point (24h). However, the transcription levels of BmPrx4 and BmPrx6 that can be addressed to secrete from the cell and cytosol, respectively, reached their peak levels at a later time point (72 h). Similar to expose to phoxim, the transcription levels of BmPrx3 and BmPrx5 that can be located in mitochondria reached their peak levels at an early time point (24 h) under chlorpyrifos stress. However, the transcription levels of BmPrx4 and BmPrx6 that can be addressed to secrete from the cell and cytosol, respectively, reached their peak levels at a later time point (72 h) under chlorpyrifos stress. These results revealed that BmPrxs that can be located in mitochondria were able to protect cells even more efficiently than cytosolic from an oxidative stress caused by OP. In addition, BmDUOX was also induced by phomix and chlorpyrifos. Overall, our results indicate that a complex expression regulation of Prxs that play important roles in maintaining redox equilibrium state of silkworm to reduce oxidative damage caused by pesticide.