Identification of the nucleotide exchange factor BmGrpE and its role under high-temperature stress in silkworm, Bombyx mori

The high-temperature stress gene GrpE plays an important role in coping with high-temperature stress. The mutation of key sites of this gene can improve the high-temperature resistance of organisms. In the present study, using complementary DNAs from the silkworm fat body as the template, the open reading frame sequence of the GrpE gene (BmGrpE) was amplified and was found to be 644 bp in length and encode a protein with a predicted molecular weight of 24.1 kDa. The presence of a binding site for the heat shock transcription factor (Hsf1) at -1440 bp upstream of its coding region indicates that BmGrpE may respond to high-temperature stress. BmGrpE was constitutively expressed throughout developmental stages, with the highest level observed in the 5th instar larvae stage. Moreover, in 5th instar larvae (the 3th day), BmGrpE was expressed in all tissues examined, with the highest levels in the fat body, silk gland, and midgut. Interestingly, under high-temperature stress, TiO2 nanoparticle treatment increased the messenger RNA levels of BmGrpE in the fat body and silk gland. After treatment with dsRNA of BmGrpE, the cell viability of BmN cells was significantly decreased under 34 degrees C and H2O2 stress (p < .05). Mutation of BmGrpE (H163L) enhanced the resistance of BmN cells under high-temperature stress. These results provide new clues for the study of molecular mechanisms of insect resistance to high temperatures.