Thermal Stress-related Genes in Honey Bees(Apis mellifera Linnaeus) by RNA-seq Analysis

The honey bee, Apis mellifera, a vital pollinator for agricultural crops, has experienced a decline in numbers over the past decades due to colony collapse disorder(CCD). The suspected causes of CCD have included climate change, parasites, and pesticide use. This study focused on the impact of climate change, as insect body temperature, which is regulated by environmental conditions, is highly susceptible to thermal stress. We investigated the molecular response processes of A. mellifera by comparing gene expression profiles under low (10°C) and high (38°C) temperature stress with those of an untreated control(25°C). RNA-seq analysis identified 349,489 assembled transcripts. Differentially expressed genes (DEGs) with a log₂ fold change≥2 were compared between the temperature conditions. We identified 2,838 DEGs at 10°C and 3,634DEGs at 38°C. Specifically, 2,077 and 2,007 genes were upregulated, while 1,438 and 3,393 genes were down- regulated at 10°C and 38°C, respectively, compared to 25°C. The honey bees exhibited increased expression of HSP70 and HSP60 genes under high-temperature stress, whereas ApoID, HR38, and ABRA genes were highly expressed under low-temperature stress. ETH, TTLL4, and OR genes were highly expressed under both temperature conditions. Our findings demonstrate that honey bees exhibit distinct transcriptomic responses to thermal stress, with HSPs mediating heat tolerance and calcium/lipid-associated genes supporting cold tolerance.