Functional analysis of small heat shock proteins providing evidence of temperature tolerance in Hyphantria cunea.

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 (Ltim50) 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 HCsHSPs presented a close evolutionary relationship with sHSP genes in noctuidae species. Four sHSPs in H. cunea were sensitive to heat stress, and only HCsHSP28.7 was induced by cold stress. The expression level of HCsHSPs peaked at 40°C and decreased in treatment at 45°C. HCsHSP20.0 transcripts were abundant in the cuticle after heat shock, and HCsHSP28.7 was most enriched in the fat body after cold shock. In addition, an equal molecular weight of the HCsHSP20.0 protein could completely protect malate dehydrogenase (MDH) from thermal aggregation. Recombinant HCsHSP28.7 E. coli cells exhibited tolerance to cold stress. Overall, our results demonstrate that HCsHSPs, especially HCsHSP20.0 and HCsHSP28.7, are vital genes in the adaptation of H. cunea larvae to extreme conditions in the context of global climate change. [ABSTRACT FROM AUTHOR]