Cold Tolerance and Differential Expression of Cuticular Protein Genes in Sungaya inexpectata Zompro, 1996 (Insecta: Phasmatodea).

Sungaya inexpectata is a tropical stick insect endemic to the Philippines, providing a useful system for investigating cold responses in tropical ectotherms. In this study, we exposed individuals to low temperature (8 °C) and normal temperature (25 °C) and characterized their transcriptomic responses. A total of 1656 differentially expressed genes were identified, including those involved in energy metabolism, cuticular proteins (CPs), and heat shock proteins. Since CP-related genes were notably enriched, we focused on this family. qPCR assessment provided preliminary expression profiles for selected candidate CP genes. Using comparative transcriptomics with eight New Zealand alpine stick insect species, we reconstructed the phylogeny of major CP families and annotated their conserved domains. Clade analysis revealed significant positive selection in the CPAP3-3 gene. In summary, this study reveals the transcriptional response of cuticular protein genes in S. inexpectata under cold exposure at 8 °C. These findings provide preliminary transcriptional data for understanding how this species responds to low temperature.