Galibert L, Devauchelle G, Cousserans F, Rocher J, Cérutti P, Barat-Houari M, Fournier P, Volkoff A N
UMR1231 INRA-UMII Biologie Intégrative et Virologie des Insectes (BIVI), Place Eugène Bataillon, Case Courrier 101, 34 095 Montpellier Cédex5, France.
Virol J. 2006 Jun 19;3:48. doi: 10.1186/1743-422X-3-48.
The abundance and the conservation of the repeated element (rep) genes in Ichnoviruses genomes suggest that this gene family plays an important role in viral cycles. In the Ichnovirus associated with the wasp Hyposoter didymator, named HdIV, 10 rep genes were identified to date. In this work, we report a relative quantitative transcription study of these HdIV rep genes in several tissues of the lepidopteran host Spodoptera frugiperda as well as in the H. didymator wasps.
The data obtained in this work indicate that, in the early phases of infection (24 hours), HdIV rep genes each display different levels of transcripts in parasitized 2nd instar or HdIV-injected last instar S. frugiperda larvae. Only one, rep1, is significantly transcribed in female wasps. Transcript levels of the HdIV rep genes were found as not correlated to their copy number in HdIV genome. Our results also show that HdIV rep genes display different tissue specificity, and that they are primarily transcribed in S. frugiperda fat body and cuticular epithelium.
This work is the first quantitative analysis of transcription of the ichnovirus rep gene family, and the first investigation on a correlation between transcript levels and gene copy numbers in Ichnoviruses. Our data indicate that, despite similar gene copy numbers, not all the members of this gene family are significantly transcribed 24 hours after infection in lepidopteran larvae. Additionally, our data show that, as opposed to other described HdIV genes, rep genes are little transcribed in hemocytes, thus suggesting that they are not directly associated with the disruption of the immune response but rather involved in other physiological alterations of the infected lepidopteran larva.
杆状病毒基因组中重复元件（rep）基因的丰度和保守性表明，该基因家族在病毒周期中发挥着重要作用。在与黄蜂双斑胯姬蜂（Hyposoter didymator）相关的杆状病毒（命名为HdIV）中，迄今为止已鉴定出10个rep基因。在这项研究中，我们报告了这些HdIV rep基因在鳞翅目宿主草地贪夜蛾（Spodoptera frugiperda）的多个组织以及双斑胯姬蜂中的相对定量转录研究。
这项研究获得的数据表明，在感染早期（24小时），HdIV rep基因在被寄生的2龄草地贪夜蛾幼虫或注射HdIV的末龄草地贪夜蛾幼虫中各自呈现出不同水平的转录本。只有一个基因rep1在雌性黄蜂中显著转录。发现HdIV rep基因的转录水平与其在HdIV基因组中的拷贝数无关。我们的结果还表明，HdIV rep基因表现出不同的组织特异性，并且它们主要在草地贪夜蛾的脂肪体和表皮上皮中转录。
这项工作是杆状病毒rep基因家族转录的首次定量分析，也是对杆状病毒转录水平与基因拷贝数之间相关性的首次研究。我们的数据表明，尽管基因拷贝数相似，但并非该基因家族的所有成员在鳞翅目幼虫感染后24小时都能显著转录。此外，我们的数据表明，与其他已描述的HdIV基因不同，rep基因在血细胞中很少转录，因此表明它们与免疫反应的破坏没有直接关联，而是参与了被感染鳞翅目幼虫的其他生理变化。
