Table_5_Transcriptome Profiling Reveals a Novel Mechanism of Antiviral Immunity Upon Sacbrood Virus Infection in Honey Bee Larvae (Apis cerana).XLSX

The honey bee is one of the most important pollinators in the agricultural system and is responsible for pollinating a third of all food we eat. Sacbrood virus (SBV) is a member of the virus family Iflaviridae and affects honey bee larvae and causes particularly devastating disease in the Asian honey bees, Apis cerana. Chinese Sacbrood virus (CSBV) is a geographic strain of SBV identified in China and has resulted in mass death of honey bees in China in recent years. However, the molecular mechanism underlying SBV infection in the Asian honey bee has remained unelucidated. In this present study, we employed high throughput next-generation sequencing technology to study the host transcriptional responses to CSBV infection in A. cerana larvae, and were able to identify genome-wide differentially expressed genes associated with the viral infection. Our study identified 2,534 differentially expressed genes (DEGs) involved in host innate immunity including Toll and immune deficiency (IMD) pathways, RNA interference (RNAi) pathway, endocytosis, etc. Notably, the expression of genes encoding antimicrobial peptides (abaecin, apidaecin, hymenoptaecin, and defensin) and core components of RNAi such as Dicer-like and Ago2 were found to be significantly upregulated in CSBV infected larvae. Most importantly, the expression of Sirtuin target genes, a family of signaling proteins involved in metabolic regulation, apoptosis, and intracellular signaling was found to be changed, providing the first evidence of the involvement of Sirtuin signaling pathway in insects’ immune response to a virus infection. The results obtained from this study provide novel insights into the molecular mechanism and immune responses involved in CSBV infection, which in turn will contribute to the development of diagnostics and treatment for the diseases in honey bees.

蜜蜂是农业生产体系中至关重要的传粉昆虫，人类膳食中约三分之一的食物产量依赖其传粉服务。囊雏病病毒（Sacbrood virus, SBV）隶属于伊夫拉病毒科（Iflaviridae），可侵染蜜蜂幼虫，且对东方蜜蜂（Apis cerana）引发尤为严重的毁灭性病害。中国囊雏病病毒（Chinese Sacbrood virus, CSBV）是SBV在中国境内发现的地理株系，近年来已在国内引发蜜蜂大规模死亡事件。然而，东方蜜蜂感染SBV的分子机制至今尚未阐明。本研究采用高通量下一代测序技术，探究东方蜜蜂幼虫感染CSBV后的宿主转录应答，并成功鉴定出与病毒侵染相关的全基因组差异表达基因。本研究共鉴定出2534个差异表达基因（differentially expressed genes, DEGs），这些基因参与宿主先天免疫过程，包括Toll通路、免疫缺陷（immune deficiency, IMD）通路、RNA干扰（RNA interference, RNAi）通路以及胞吞作用等。值得注意的是，在感染CSBV的幼虫体内，编码抗菌肽（包括abaecin、apidaecin、hymenoptaecin及defensin）以及RNAi通路核心组分（如类Dicer蛋白（Dicer-like）和Argonaute 2 (Ago2)）的基因表达均显著上调。尤为关键的是，沉默信息调节因子（Sirtuin）靶基因的表达发生显著改变——该家族信号蛋白参与代谢调控、细胞凋亡及细胞内信号传导过程——本研究首次证实沉默信息调节因子信号通路参与昆虫对病毒侵染的免疫应答。本研究结果为解析CSBV侵染的分子机制与宿主免疫应答提供了全新视角，同时也将助力蜜蜂相关病害的诊断与治疗手段开发。