Real and Apparent Complexity in Polydnavirus Genomes

Webb 9603504多DNA病毒的基因组和生命周期是复杂的。Campoletissomnorensis（PDV）具有至少28个DNA片段，基因组大小估计超过250kb，其中最丰富表达的是嵌套的。人们对驱动或允许病毒基因组分段的进化压力知之甚少。PDV是一些寄生性Hyplitera的专性共生体，并且仅在雌性生殖道的专门的萼细胞中从整合的前病毒DNA渐进地复制。当黄蜂寄生鳞翅目宿主时，病毒基因组侵入宿主，停止复制，病毒基因以恒定水平快速表达，产生感染。这种病毒基因表达是成功发育的内寄生蜂所必需的。PDV基因组分段导致高水平的基因表达在寄生昆虫的选择压力的假设将通过克隆和定位基因的嵌套病毒DNA片段，通过评估一些病毒结构蛋白和通过操纵宿主昆虫中的病毒基因表达水平进行测试。 这些研究的结果将产生第一个全面表征的多DNA病毒基因组，允许关键的评价之间的联系段嵌套和水平的基因表达，并可能产生基本的洞察力的进化力量，形成了多DNA病毒的基因组，唯一的一组分段的DNA病毒。

Webb 9603504 Polydnavirus genomes and life cycles are complex. Campoletis somnorensis (PDV) has at least 28 DNA segments with genome size estimates in excess of 250 kb, of which the most abundantly expressed are nested. There is little understanding of the evolutionary pressures that have driven or allowed segmentation of the viral genome. PDVs are obligate symbionts of some parasitic hymenoptera and replicate asymptotically from integrated proviral DNA only in specialized calyx cells of the female reproductive tract. When the wasp paristizes the lepidopteran host, the virus genome invades the host, ceases replicating and viral genes are rapidly expressed at a constant level producing infection. Such viral gene expression is required for successful development of the endoparasitic wasp. The hypothesis that PDV genome segmentation has resulted from selective pressure for high level gene expression in parasitized insects will be tested by cloning and mapping genes on nested viral DNA segments, by evaluating a number of viral structural proteins and by manipulating the level of viral gene expression in host insects. The results of these studies will produce the first comprehensive characterization of a polydnavirus genome allowing critical evaluation of the linkage between segment nesting and levels of gene expression and may produce fundamental insights into the evolutionary forces that have shaped the genomes of polydnaviruses, the only group of segmented DNA viruses.