Harwood S H, Grosovsky A J, Cowles E A, Davis J W, Beckage N E
Department of Entomology, University of California at Riverside 92521-0314.
Virology. 1994 Dec;205(2):381-92. doi: 10.1006/viro.1994.1659.
Cotesia congregata polydnavirus (CcPDV) is essential for successful parasitism of Manduca sexta larvae by the braconid wasp C. congregata. CcPDV virions are present in large numbers in the oviducts of C. congregata and injected with eggs into the hemocoel of M. sexta larvae during parasitization. Injection of sucrose density purified virions into nonparasitized larvae causes several of the parasitism-induced alterations in the physiology of host larvae that occur as a result of natural parasitism, including the synthesis of novel hemolymph proteins and abrogation of the host's immune response against the developing parasites. One of these proteins, early-expressed protein 1 (EP1), is a 190-kDa molecule which constitutes up to 5% of the total hemolymph protein by 24 hr following oviposition by the wasp. Using N-terminal sequence data for EP1 to construct primers for use in the polymerase chain reaction, we amplified and cloned a cDNA corresponding to the gene encoding EP1. This cDNA hybridized to DNA of the CcPDV genome, but not to DNA isolated from M. sexta larvae, suggesting that EP1 is a CcPDV gene product. A cDNA clone was isolated from an expression library generated from RNA extracted from newly parasitized M. sexta larvae. Sequence analysis of the cDNA clone revealed the presence of an open reading frame of 819 bp encoding a protein of 30.7 kDa. In vitro transcription/translation of the cDNA clone produced a protein of approximately 31 kDa, which was immunoprecipitated by EP1-specific polyclonal antiserum generated against purified deglycosylated EP1. EP1-like sequences also were amplified from male wasp genomic DNA, suggestive of integration of EP1-like sequences in the genome. This report constitutes the first evidence that a specific protein isolated from a parasitized host insect is a wasp polydnavirus gene product.
聚瘤姬蜂多角体病毒（CcPDV）对于茧蜂科昆虫聚瘤姬蜂成功寄生烟草天蛾幼虫至关重要。CcPDV病毒粒子大量存在于聚瘤姬蜂的输卵管中，并在寄生过程中随卵注入烟草天蛾幼虫的血腔。将经蔗糖密度梯度纯化的病毒粒子注入未被寄生的幼虫，会引发宿主幼虫生理上一些因自然寄生而产生的、由寄生诱导的变化，包括合成新的血淋巴蛋白以及消除宿主对发育中寄生虫的免疫反应。这些蛋白之一，早期表达蛋白1（EP1），是一种190 kDa的分子，在黄蜂产卵后24小时内，其含量可占血淋巴蛋白总量的5%。利用EP1的N端序列数据构建用于聚合酶链反应的引物，我们扩增并克隆了一个与编码EP1的基因相对应的cDNA。该cDNA与CcPDV基因组的DNA杂交，但不与从烟草天蛾幼虫中分离的DNA杂交，这表明EP1是CcPDV的基因产物。从新被寄生的烟草天蛾幼虫提取的RNA构建的表达文库中分离出一个cDNA克隆。对该cDNA克隆的序列分析显示存在一个819 bp的开放阅读框，编码一个30.7 kDa的蛋白质。对该cDNA克隆进行体外转录/翻译产生了一个约31 kDa的蛋白质，该蛋白质可被针对纯化的去糖基化EP1产生的EP1特异性多克隆抗血清免疫沉淀。从雄性黄蜂基因组DNA中也扩增出了类似EP1的序列，这表明类似EP1的序列整合到了基因组中。本报告首次证明，从被寄生的宿主昆虫中分离出的一种特定蛋白质是黄蜂多角体病毒的基因产物。
