mRNA and Small RNA-seq Reveal Insights into Immune Regulation in Apis cerana after Chinese Sacbrood Virus Infection

ABSTRACTChinese sacbrood virus (CSBV) is a serious threat to eastern honeybees (Apis cerana), especially larvae. However, the pathological mechanism of this deadly disease is remains unclear. Here, we employed an mRNA-seq and sRNA-seq approach in healthy and CSBV-infected 3rd Apis cerana larval. Gene ontology (GO) and KEGG analysis of 203 differentially expressed genes showed that CSBV infection affected host development by up-regulating the expression of larval cuticle proteins, such as larval cuticle proteins A1A and A3A, resulting in elevated susceptibility to CSBV. In addition, viral infection not only affected the expression of serine protease related to the melanization pathway and but also altered fatty acid metabolism and biosynthesis, thus progressed to disturb host immune response. Interestingly, GO annotation and KEGG analysis on target genes of CSBV-specific siRNA (vsiRNAs) showed that serine/threonine kinase activity and serine-type endopeptidas as well as fatty acid biosynthesis were significantly enriched (P < 0.05). Among these vsiRNAs, vsiRNA-1441 with relatively high expression targeted extracellular serine/threonine protein kinase. This study provides new evidence that CSBV attacks a distinct immune response pathway and mediates the expression of cuticle protein to gain the more chance of proliferation.IMPORTANCE Chinese sacbrood virus (CSBV) is the major factor threatening the health of Apis cerana. Although honeybees have antiviral defense mechanisms including RNA-interference (RNAi), virus had evolved resistance strategy like virus-derived small interfering RNAs (vsiRNA) produced during the viral infection, which can alter host immune by hijacking the host RNAi pathway. To gain insights at the transcription level into the mechanisms vsiRNA altering immune response and how this variation is connected with CSBV infection, we performed the first combined mRNA and small RNA-seq analyses of healthy and CSBV-infected Apis cerana larvae. Together, the omics approach enabled us to obtain comprehensive results that CSBV infection changed the expressions of cuticle proteins and related serine protease, and leading to the larvae unable to pupate. This will guide the design of new strategies for control CSBV.View Full Text