Roles of SfHSP70-7 in Thermal Tolerance, Insecticide Adaptability, and Reproductive Performance Under Combined Environmental Stress of the Rice Pest Sogatella furcifera (Hemiptera: Delphacidae).

Heat shock protein 70 (HSP70) regulates the stress tolerance and reproductive ability of insects. In this study, the SfHSP70-7 gene was cloned and identified from the rice pest Sogatella furcifera. SfHSP70-7 encodes a typical cytoplasmic HSP70 protein that has a conserved functional domain and is highly similar to the HSP70 homologous protein of Laodelphax striatellus. SfHSP70-7 was found to be widely expressed across all developmental stages, with the highest levels in nymphs and female adults. In terms of tissue distribution, it was particularly abundant in the gut and ovaries. Its expression was strongly induced by high/low temperatures and three insecticides (triflumezopyrim, sulfoxaflor, and imidacloprid), with the maximum induction under heat and triflumezopyrim stress. RNA interference (RNAi) efficiently silenced SfHSP70-7 and significantly increased the susceptibility of S. furcifera to triflumezopyrim and sulfoxaflor, but it had no effect on susceptibility to imidacloprid. RNAi knockdown of SfHSP70-7 markedly reduced survival by 45.5% (30 °C) and 38.9% (35 °C) under heat stress. In addition, gene knockdown can damage the reproductive performance of females by reducing oviposition and egg hatchability. These results indicate that SfHSP70-7 is involved in regulating the heat tolerance, insecticide adaptability, and reproductive regulation mechanism of S. furcifera, providing a potential target for pest control.