Characterizing Three Heat Shock Protein 70 Genes of Aphis gossypii and Their Expression in Response to Temperature and Insecticide Stress

Aphis gossypii is a highly polyphagous pest that causes substantial agricultural damage. Temperature and insecticides are two major abiotic stresses affecting their population abundance. Heat shock proteins play an essential role in cell protection when insects are exposed to environmental stresses. Three ApHsp70 genes were cloned from A. gossypii, and characterized their molecular features and expression profiles in response to temperature and insecticide stress. The deduced amino acid sequences of these proteins exhibited characteristic Hsp70 family signatures, and their tissue-specific expression patterns revealed their highest activity to be in the salivary glands under 35 °C. The temperature inductive assay further indicated that the expression of the three ApHsp70 genes was markedly upregulated under heat stress but not under cold shock. Furthermore, exposure to LC25 and LC50 concentrations of three insecticides triggered the upregulation of these ApHsp70 genes. The RNA interference (RNAi)-mediated suppression of ApHsp68 expression heightened cotton aphid's susceptibility to insecticides (acetamiprid and sulfoxaflor). Moreover, our study found that the sulfoxaflor-resistant strain of A. gossypii (Sul-R) displayed a higher survival rate compared with the sulfoxaflor-sensitive strain (Sul-S) under heat shock conditions. These results suggest that these three ApHsp70 genes play an essential role in response to both heat and insecticide stress.