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

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 (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.

Sequential expression of small heat shock proteins contributing to the cold response of Haemaphysalis longicornis (Acari: Ixodidae)

“…This may be attributed to the fact that the temperature will exceed the regulatory range of sHsps on the body with the time extension, resulting in the stagnation of the gene transcription. 39 Similar results were also found in Hyphantria cunea, where the expression of HCsHsp28.7 showed a fluctuating trend of first increasing and then declining with the time extension after treatment at −10 °C for 1, 2, and 3 h. 40 GpHSP21.4 in Glyphodes pyloalis was downregulated at 4 h following exposure to cold treatment. 41 These results indicated that the response of sHsps to low-temperature stress at the transcription level depends on the severity and duration of the low temperature.…”

Spatiotemporal Patterns of Five Small Heat Shock Protein Genes in Hyphantria cunea in Response to Thermal Stress

“…We found that the relative expression levels of HcHSPs, except for HcHSP21.4, were significantly up-regulated under heat stress and continued to increase with the increase in temperature stress. In previous studies, four of the six identified sHSPs were sensitive to high temperatures [35]. These results indicate that H. cunea has strong heat tolerance, which may enhance its survival as it spreads to the warmer southern areas of China.…”

“…Our previous investigations revealed that the Ltim50 values for H. cunea 4th-instar larvae were 62.0 h at 40 • C, 14.5 h at 43 • C, and even 2.3 h at 45 • C [35]. To consider the differences in the thermotolerance of H. cunea at different developmental stages, we set the treatment duration to one hour and used 43 • C as the upper temperature limit.…”