Characterization and expression of heat shock protein 70s in Liposcelis bostrychophila: Insights into their roles in insecticidal stress response

Liposcelis bostrychophila is one of the most economically significant and important storage pests in the Psocoptera order. Heat shock proteins (HSPs) act as molecular chaperones and play an important role in insect responses to environmental stress. In this study, the genome-wide identification and characterization of 61 HSP proteins in the L. bostrychophila genome was conducted. These HSPs are classified into five different families, comprising 8 HSP70s, 3 HSP90s, 10 HSP60s, 35 HSP40s, and 5 sHSPs genes. Phylogenetic profiling of the HSP gene families disclosed unique inter-group connections for each HSP family. These families maintained relatively stable motif composition and gene structure. Particularly, the HSP40 family expanded substantially in L. bostrychophila. Furthermore, quantitative polymerase chain reaction (qPCR) revealed distinct expression profiles of the LbHSP genes during development of L. bostrychophila. Most LbHSP70 genes expression are induced by insecticide exposures, and differences in their mRNA abundance profiles may be associated with the type and concentration of the tested insecticides. Specifically, LbHSP70.4 and LbHSP70.5 were most significantly up-regulated after insecticide treatments. Silencing the expression of LbHSP70.4 and LbHSP70.5, respectively, resulted in significantly higher mortality upon both beta-cypermethrin and malathion (LC20) treatments. This study affirms the important roles played by specific LbHSP70 genes in responding to insecticide stresses. The findings of this study not only contribute to the database of insect heat shock protein genes but also enhance our understanding of the mechanism underlying resistance or tolerance formation in stored-product psocids.