Abstract

A substantial increase in the occurrence of extremely high- or low-temperature events caused by global climate change has imposed pressure on the survival and reproduction of invertebrates. Hyphantria cunea ( H. cunea ; Lepidoptera: Arctiidae) is a worldwide defoliator and has become a major forestry and agricultural pest during the past three decades in China. The thermal and cold tolerance has directly affected the population and geographical distribution of H. cunea , which remains poorly understood. Here, we examined the thermal tolerance of H. cunea larvae and discovered that they could endure extremely high temperatures, as demonstrated by median lethal times (Ltim 50 ) of 103.3 hr at 37°C, 62.0 hr at 40°C and even 14.5 hr at 43°C. To further explore the molecular evidence of the physiological response to heat and cold, we cloned and characterized six small heat shock proteins (sHSPs). These proteins possessed the conserved α-domain of the sHSP family at the C-terminus and various N-terminal domains. Phylogenetic analysis showed that the HC sHSPs presented a close evolutionary relationship with sHSP genes in noctuidae species. Four sHSPs in H. cunea were sensitive to heat stress, and only HC sHSP28.7 was induced by cold stress. The expression level of HC sHSPs peaked at 40°C and decreased in treatment at 45°C. HC sHSP20.0 transcripts were abundant in the cuticle after heat shock, and HC sHSP28.7 was most enriched in the fat body after cold shock. In addition, an equal molecular weight of the HC sHSP20.0 protein could completely protect malate dehydrogenase (MDH) from thermal aggregation. Recombinant HC sHSP28.7 E. coli cells exhibited tolerance to cold stress. Overall, our results demonstrate that HC sHSPs, especially HC sHSP20.0 and HC sHSP28.7, are vital genes in the adaptation of H. cunea larvae to extreme conditions in the context of global climate change.