Abstract: The purified Ascosphaera apis spores and the 6-day-old larval gut of Apis mellifera ligustica under the stress of A. apis were sequenced using RNA-seq technology to detect gene expression patterns of the fungal pathogen. A total of 21 361 differentially expressed genes (DEGs) were obtained, including 15 306 up-regulated genes and 6 055 down-regulated genes. GO enrichment analysis showed that the up-regulated genes were enriched in 39 terms, among them the mostly enriched ones were cellular process (2 416 unigenes), cell (2 408 unigenes) and cell part (2 408 unigenes); the down-regulated genes were enriched in 38 terms, and the mostly enriched ones were metabolic process (1 227 unigenes), cellular process (1 185 unigenes) and cell (1 131 unigenes). KEGG enrichment analysis displayed that the up-regulated genes were enriched in 119 pathways, and the largest groups were ribosome (221 unigenes), protein processing in endoplasmic reticulum (190 unigenes) and endocytosis (177 unigenes); the down-regulated genes were enriched in 113 pathways, and the mostly enriched ones were ribosome (144 unigenes), RNA transport (113 unigenes) as well as biosynthesis of amino acid (108 unigenes). Furthermore, 64 up-regulated genes were found to be enriched in MAPK signaling pathway, suggesting that it was induced to a large extent. The data not only provided key information for uncovering the pathogen-host interaction during the late stage of the stress of A. apis on A. m. ligustica larvae, but also laid some foundation for clarifying molecular mechanisms regulating the pathogenesis of A. apis.

Key words: Ascosphaera apis, Apis mellifera ligustica, larval gut, DEGs, RNA-seq