<scp>HcTRET1</scp> is critical for epidermal chitin synthesis in <i>Hyphantria cunea</i>

In insects, trehalose is critical for growth and development, as well as environmental stress response, which is mainly transported by trehalose transporters (TRETs). Over nearly two decades, the physiological functions of TRETs in insect growth, development, reproduction and environmental stress response have been well elucidated. However, the role of TRETs in chitin synthesis remains not fully understood. Here, we identified the HcTRET1 gene from Hyphantria cunea, a major Lepidoptera pest in agriculture and forestry. The role of HcTRET1 in growth and development, especially in chitin synthesis, was discussed by dsRNA-mediated HcTRET1 knockdown. Bioassay showed that HcTRET1 knockdown did not affect larval growth, development and survival in H. cunea, but it significantly reduced the pupa formation rate. Additionally, HcTRET1 silencing increased trehalose levels in the fat body but decreased them in the hemolymph, suggesting HcTRET1 plays a key role in trehalose homeostasis. Moreover, HcTRET1 knockdown significantly downregulated the genes for chitin synthesis (HcGFAT, HcUAP and HcCHSA), resulting in a remarkable reduction of chitin content in the epidermis. Moreover, HcTRET1 knockdown significantly reduced the survival of H. cunea larvae at 42°C. Taken together, these results demonstrated that HcTRET1 played a critical role in larva-pupa transition, in vivo trehalose homeostasis, especially in epidermal chitin biosynthesis in H. cunea larvae. In parallel, its important physiological function in response to high-temperature stress has been verified as well. The findings expand our understanding of the physiological functions of TRET1 in insects, providing a new perspective for trehalose transporters to regulate chitin biosynthesis.