High-Humidity Stress Response in Faba Bean Aphids (Megoura crassicauda): Insights From Transcriptomic Analysis

High-humidity environments can inhibit the reproduction of faba bean aphids (Megoura crassicauda), reduce their moisture content, and induce the emergence of long-winged aphids. However, little is currently known about the molecular mechanisms through which M. crassicauda adapts to high-humidity stress. To better understand the adaptive mechanisms of M. crassicauda under high relative humidity (RH) conditions, we examined their gene expression under three different RH treatments (60%, 75%, and 90%). Differentially expressed genes (DEGs) and related biological processes were identified using transcriptome analysis. Based on the transcriptomic data, several genes with significant expression differences were identified, and their expression patterns under different humidity conditions were validated by qRT-PCR. In the comparisons of RH 60% versus RH 75%, RH 60% versus RH 90%, and RH 75% versus RH 90%, we observed 44, 552, and 268 upregulated genes, and 17, 1536, and 1075 downregulated genes, respectively. Three key pathways, specifically the PI3K/Akt, AMPK, and insulin signaling pathway, were found to be responsive to high-humidity stress, with a greater number of genes downregulated at RH 90%. Additionally, heat shock proteins (HSPs) and zinc finger proteins (ZFPs) were significantly differentially expressed under high humidity, highlighting their crucial roles in the stress response. These findings provide valuable insights into the genes and metabolic signaling pathways involved in high-humidity stress response, laying the foundation for future research on the molecular mechanisms of M. crassicauda adaptation and identifying potential target genes for pest control.