The Iflaviruses Sacbrood virus and Deformed wing virus evoke different transcriptional responses in the honeybee which may facilitate their horizontal or vertical transmission.
The Iflaviruses Sacbrood virus and Deformed wing virus evoke different transcriptional responses in the honeybee which may facilitate their horizontal or vertical transmission.
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作者：
Ryabov EV;Fannon JM;Moore JD;Wood GR;Evans DJ
Sacbrood病毒(SBV)和变形翼病毒(DWV)是进化上相关的正链RNA病毒，属于Ifla病毒组成员。这两种病毒都能感染蜜蜂，但在口头传播时，它们的毒力水平却截然不同。口服感染SBV的蜜蜂幼虫通常会积累高水平的病毒，这会阻止幼虫的发育，并导致昆虫死亡。相比之下，在幼虫阶段经口感染DWV通常会导致病毒水平较低的无症状感染，尽管摄入高剂量的DWV会导致DWV复制到高水平。利用全局RNA-Seq和实时荧光定量聚合酶链式反应(Real-Time-PCR)技术，研究了DWV和SBV感染对蜜蜂幼虫和蛹转录组的影响。这表明，高水平的SBV复制导致角质层和肌肉发育相关基因的下调，以及可能的免疫相关基因表达的变化。特别是，具有高水平SBV复制的蜜蜂幼虫，无论是否有高水平的DWV复制，都表现出抗菌肽(AMP)的协同上调，以及酚氧化酶激活酶(PPAE)的下调，以及可能导致黑化途径抑制的丝氨酸的表达。高水平的SBV对这些免疫基因表达的影响不太可能是SBV诱导的发育变化的结果，因为在注射感染的蜜蜂蛹中也观察到了类似的影响。在仅有高水平DWV复制的经口感染的幼虫中，我们没有观察到AMP或黑化途径中基因表达的变化。在注射的蚕蛹中，高水平的DWV单独并不改变所测试的黑化途径基因的表达，但导致AMP的上调，这可能归因于DWV对AMP表达的调节以响应伤害。我们认为，SBV和DWV诱导的蜜蜂免疫基因表达的差异可能是对这两种病毒所使用的不同主要传播途径的进化适应。
Sacbrood virus (SBV) and Deformed wing virus (DWV) are evolutionarily related positive-strand RNA viruses, members of the Iflavirus group. They both infect the honeybee Apis mellifera but have strikingly different levels of virulence when transmitted orally. Honeybee larvae orally infected with SBV usually accumulate high levels of the virus, which halts larval development and causes insect death. In contrast, oral DWV infection at the larval stage usually causes asymptomatic infection with low levels of the virus, although high doses of ingested DWV could lead to DWV replicating to high levels. We investigated effects of DWV and SBV infection on the transcriptome of honeybee larvae and pupae using global RNA-Seq and real-time PCR analysis. This showed that high levels of SBV replication resulted in down-regulation of the genes involved in cuticle and muscle development, together with changes in expression of putative immune-related genes. In particular, honeybee larvae with high levels of SBV replication, with and without high levels of DWV replication, showed concerted up-regulated expression of antimicrobial peptides (AMPs), and down-regulated expression of the prophenoloxidase activating enzyme (PPAE) together with up-regulation of the expression of a putative serpin, which could lead to the suppression of the melanisation pathway. The effects of high SBV levels on expression of these immune genes were unlikely to be a consequence of SBV-induced developmental changes, because similar effects were observed in honeybee pupae infected by injection. In the orally infected larvae with high levels of DWV replication alone we observed no changes of AMPs or of gene expression in the melanisation pathway. In the injected pupae, high levels of DWV alone did not alter expression of the tested melanisation pathway genes, but resulted in up-regulation of the AMPs, which could be attributed to the effect of DWV on the regulation of AMP expression in response to wounding. We propose that the difference in expression of the honeybee immune genes induced by SBV and DWV may be an evolutionary adaptation to the different predominant transmission routes used by these viruses.