Global analysis of baculovirus Autographa californica Multiple Nucleopolyhedrovirus (AcMNPV) gene expression in the midgut of the Trichoplusia ni larvae. Trichoplusia ni strain:cornell

The baculovirus AcMNPV is a large dsDNA virus that encodes approximately 156 genes and is highly pathogenic to a variety of larval lepidopteran insects in nature. Oral infection of larval midgut cells is initiated by the occlusion derived virus (ODV), while secondary infection of other tissues is mediated by the budded virus (BV). Global viral gene expression has been studied in detail in BV-infected cell cultures, but studies of ODV-infection in the larval midgut are limited. In this study, we examined expression of the ~156 AcMNPV genes in Trichoplusia ni midgut tissue using a transcriptomic approach. We analyzed expression profiles of viral genes in the midgut, and compared them with profiles from a T. ni cell line (Tnms42). Several viral genes (p6.9, orf76, orf75, pp31, Ac-bro, odv-e25, and odv-ec27) had high expression levels in the midgut throughout the infection. Also, the expression of genes associated with occlusion bodies (polh and p10) appeared to be delayed in the midgut in comparison with the cell line. Comparisons of overall viral gene expression profiles revealed remarkable similarities between the midgut and cell line for most genes, although substantial differences were also observed for some viral genes. These included genes associated with high level BV production (fp-25k), acceleration of systemic infection (v-fgf), and enhancement of viral movement (arif-1/orf20). These differential expression patterns appear to represent specific adaptations for virus infection and movement through the polarized cells of the lepidopteran midgut.

杆状病毒AcMNPV是一类大型双链DNA病毒，其基因组编码约156个基因，在自然环境中对多种鳞翅目幼虫具有高致病性。幼虫中肠细胞的口服感染由包涵体衍生病毒（occlusion derived virus, ODV）启动，而其他组织的继发感染则由出芽病毒（budded virus, BV）介导。目前针对BV感染细胞培养体系的病毒全局基因表达已开展详尽研究，但有关ODV感染幼虫中肠的相关研究仍较为匮乏。本研究采用转录组学方法，对粉纹夜蛾（Trichoplusia ni）中肠组织内约156个AcMNPV基因的表达情况进行了检测。我们分析了该病毒在中肠中的基因表达谱，并将其与粉纹夜蛾细胞系Tnms42的表达谱进行了对比。多个病毒基因（p6.9、orf76、orf75、pp31、Ac-bro、odv-e25及odv-ec27）在整个感染进程中的中肠组织内均维持高表达水平。此外，与包涵体相关的基因polh与p10在中肠中的表达相较于细胞系出现明显延迟。对整体病毒基因表达谱的比较结果显示，尽管部分病毒基因存在显著差异，但多数基因在中肠与细胞系间的表达模式极为相似。这些差异表达基因包括与高水平BV产生相关的fp-25k、加速全身感染的v-fgf，以及增强病毒移动能力的arif-1/orf20。上述差异表达模式似乎代表了病毒为通过鳞翅目幼虫中肠的极化细胞完成感染与移动所演化出的特异性适应性机制。