Johner A, Stettler P, Gruber A, Lanzrein B
J Gen Virol. 1999 Jul;80 ( Pt 7):1847-1854. doi: 10.1099/0022-1317-80-7-1847.
The parasitoid Chelonus inanitus (Braconidae, Hymenoptera) oviposits into eggs of Spodoptera littoralis (Noctuidae, Lepidoptera) and, along with the egg, also injects polydnaviruses and venom, which are prerequisites for successful parasitoid development. The parasitoid larva develops within the embryonic and larval stages of the host, which enters metamorphosis precociously and arrests development in the prepupal stage. Polydnaviruses are responsible for the developmental arrest and interfere with the host's endocrine system in the last larval instar. Polydnaviruses have a segmented genome and are transmitted as a provirus integrated in the wasp's genome. Virions are only formed in female wasps and no virus replication is seen in the parasitized host. Here it is shown that very small amounts of viral transcripts were found in parasitized eggs and early larval instars of S. littoralis. Later on, transcript quantities increased and were highest in the late last larval instar for two of the three viral segments tested and in the penultimate to early last larval instar for the third segment. These are the first data on the occurrence of viral transcripts in the host of an egg-larval parasitoid and they are different from data reported for hosts of larval parasitoids, where transcript levels are already high shortly after parasitization. The analysis of three open reading frames by RT-PCR revealed viral transcripts in parasitized S. littoralis and in female pupae of C. inanitus, indicating the absence of host specificity. For one open reading frame, transcripts were also seen in male pupae, suggesting transcription from integrated viral DNA.
寄生蜂内氏螯蜂（茧蜂科，膜翅目）将卵产入埃及棉铃虫（夜蛾科，鳞翅目）的卵中，并随卵一起注入多角体病毒和毒液，这些是寄生蜂成功发育的先决条件。寄生蜂幼虫在宿主的胚胎和幼虫阶段发育，宿主早熟进入变态并在蛹前期停止发育。多角体病毒导致发育停滞，并在宿主最后一龄幼虫期干扰其内分泌系统。多角体病毒具有分段基因组，以整合在黄蜂基因组中的前病毒形式传播。病毒粒子仅在雌蜂中形成，在被寄生的宿主中未见病毒复制。本文表明，在被寄生的埃及棉铃虫卵和早期幼虫中发现了极少量的病毒转录本。后来，转录本数量增加，在所测试的三个病毒片段中的两个片段中，最后一龄幼虫后期转录本数量最高，第三个片段在倒数第二龄到最后一龄幼虫早期转录本数量最高。这些是关于卵-幼虫寄生蜂宿主中病毒转录本出现情况的首批数据，它们与幼虫寄生蜂宿主的报道数据不同，在幼虫寄生蜂宿主中，寄生后不久转录水平就已经很高。通过逆转录聚合酶链反应对三个开放阅读框进行分析，发现在被寄生的埃及棉铃虫和内氏螯蜂雌蛹中有病毒转录本，表明不存在宿主特异性。对于一个开放阅读框，在雄蛹中也发现了转录本，这表明整合的病毒DNA发生了转录。
