Highly-expressed gene differences between Ascosphaera apis stressing the larval gut of Apis mellifera ligustica and the pure culture of Ascosphaera apis

Abstract:

[Background] Ascosphaera apis is a special fungal pathogen that specially infect honeybee larvae. Currently, information related to gene expression of A. apis during the infection process is limited. [Objective] This study was designed to analyze highly-expressed genes (HEGs) differences between A. apis stressing the 6-day-old larval gut of Apis mellifera ligustica and the pure culture of A. apis, and to explore the gene expression of A. apis during the late stage of stress and the pure culture of A. apis. [Methods] In our study, the 6-day-old larval gut of A. m. ligustica under the stress of A. apis and the pure culture of A. apis were sequenced using RNA-Seq, and the HEGs were obtained based on FPKM value, followed by function prediction and exploration of biological significance via GO (Gene ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway enrichment as well as Venn analyses. [Results] A total of 105 447 578 raw reads were produced from RNA-Seq, and 88 466 344 clean reads with a mean Q20 of 97.50% and a mean Q30 of 93.81% were obtained after filtration. GO enrichment analysis showed that the HEGs of AaCK were enriched in 26 GO terms, among them the cell (22 unigenes), cell part (22 unigenes) and metabolism (21 unigenes) were mostly enriched; the HEGs of AamT were enriched in 22 GO terms, and the mostly enriched ones were the catalytic activity (23 unigenes), cell processes (18 unigenes) and metabolic processes (18 unigenes). KEGG pathway enrichment analysis showed that the HEGs of AaCK were involved in 109 pathways, among them the largest group was ribosome (179 unigenes) followed by biosynthesis of amino acids (70 unigenes) and carbon metabolism (62 unigenes); the HEGs of AaCK were involved in 114 pathways, and the mostly enriched one was ribosome (178 unigenes) followed by carbon metabolism (116 unigenes) and oxidative phosphorylation (112 unigenes). Furthermore, Venn analysis suggested that there are 260 shared HEGs, while 2 161 and 4 445 HEGs were specially expressed in AaCK and AamT, respectively. [Conclusion] Findings in the present study can offer the expression profiles of HEGs of A. apis stressing the 6-day-old larval gut of A. m. ligustica and the pure culture of A. apis, reveal the gene expression rules of A. apis before stress and A. apis during the late stage of stress, and provide helpful information for uncovering molecular mechanisms regulating the pathogenesis of A. apis.

Key words:RNA-Seq, Apis mellifera ligustica, Larval gut, Ascosphaera apis, Highly expressed gene