Real and Apparent Complexity in Polydnavirus Genomes

多dna病毒的基因组和生命周期是复杂的。睡眠Campoletis somnorensis （PDV）至少有28个DNA片段，基因组大小估计超过250 kb，其中最丰富的表达是巢状的。人们对驱动或允许病毒基因组分割的进化压力知之甚少。pdv是一些寄生性膜翅目昆虫的专性共生体，仅在雌性生殖道的特殊花萼细胞中从整合的原病毒DNA渐近复制。当寄生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迅速表达，产生感染。这种病毒基因的表达是成功发展内生寄生蜂所必需的。PDV基因组分割是由被寄生昆虫高水平基因表达的选择压力造成的假设，将通过克隆和定位巢状病毒DNA片段上的基因，通过评估一些病毒结构蛋白和通过操纵宿主昆虫的病毒基因表达水平来验证。这些研究的结果将产生多DNA病毒基因组的第一个综合特征，允许对片段嵌套和基因表达水平之间的联系进行批判性评估，并可能产生对形成多DNA病毒基因组的进化力量的基本见解，多DNA病毒是唯一一组分段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.