Transcriptional profiling reveals the molecular bases of immune regulation in Apis mellifera in response to Ascosphaera apis infection

Chalkbrood, which results from Ascosphaera apis infection, is one of the bee diseases that causes serious damage to the bee colony. Understanding the molecular bases underlying immune response to chalkbrood disease would facilitate the genetic breeding of bees by selecting races with superior chalkbrood resistance. In this study, transcriptome sequencing was performed to identify genes and pathways involved in the immune response to As. apis infection in A. mellifera larvae. In total, 2,890 differentially expressed genes (DEGs) (FDR < 0.001) were identified between the healthy and As. apis infected bee larvae, including 2,214 up-regulated and 676 down-regulated unigenes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway classification of the DEGs revealed association with development, energy metabolism, signal transduction, disease, and immune response. Among the immune-related genes, p38, toll-like receptors (TLRs), integrin, and antimicrobial peptides were up-regulated under As. apis infection. This study provides valuable gene transcriptional information towards the investigation of molecular mechanisms related to chalkbrood immune response and host pathogenesis in A. mellifera.