School of Biological Sciences, The University of Queensland, St Lucia QLD 4072 Australia.
BMC Genomics. 2011 Sep 9;12:446. doi: 10.1186/1471-2164-12-446.
Parasitoid insects manipulate their hosts' physiology by injecting various factors into their host upon parasitization. Transcriptomic approaches provide a powerful approach to study insect host-parasitoid interactions at the molecular level. In order to investigate the effects of parasitization by an ichneumonid wasp (Diadegma semiclausum) on the host (Plutella xylostella), the larval transcriptome profile was analyzed using a short-read deep sequencing method (Illumina). Symbiotic polydnaviruses (PDVs) associated with ichneumonid parasitoids, known as ichnoviruses, play significant roles in host immune suppression and developmental regulation. In the current study, D. semiclausum ichnovirus (DsIV) genes expressed in P. xylostella were identified and their sequences compared with other reported PDVs. Five of these genes encode proteins of unknown identity, that have not previously been reported.
De novo assembly of cDNA sequence data generated 172,660 contigs between 100 and 10000 bp in length; with 35% of > 200 bp in length. Parasitization had significant impacts on expression levels of 928 identified insect host transcripts. Gene ontology data illustrated that the majority of the differentially expressed genes are involved in binding, catalytic activity, and metabolic and cellular processes. In addition, the results show that transcription levels of antimicrobial peptides, such as gloverin, cecropin E and lysozyme, were up-regulated after parasitism. Expression of ichnovirus genes were detected in parasitized larvae with 19 unique sequences identified from five PDV gene families including vankyrin, viral innexin, repeat elements, a cysteine-rich motif, and polar residue rich protein. Vankyrin 1 and repeat element 1 genes showed the highest transcription levels among the DsIV genes.
This study provides detailed information on differential expression of P. xylostella larval genes following parasitization, DsIV genes expressed in the host and also improves our current understanding of this host-parasitoid interaction.
寄生性昆虫通过在寄生时向宿主注入各种因子来操纵宿主的生理机能。转录组学方法为在分子水平上研究昆虫宿主-寄生蜂相互作用提供了一种强大的方法。为了研究一种姬蜂（半闭弯尾姬蜂）对宿主（小菜蛾）的寄生作用，本研究采用短读长深度测序方法（Illumina）分析了幼虫转录组图谱。与姬蜂寄生相关的共生多DNA 病毒（PDVs），称为姬病毒，在宿主免疫抑制和发育调控中发挥重要作用。在本研究中，鉴定了小菜蛾中的半闭弯尾姬蜂姬病毒（DsIV）基因，并与其他报道的 PDV 进行了序列比较。其中 5 个基因编码的蛋白具有未知的身份，以前没有报道过。
cDNA 序列数据的从头组装产生了 172660 个长度在 100 到 10000bp 之间的 contigs；其中 35%的长度大于 200bp。鉴定出的 928 种昆虫宿主转录本的表达水平受到寄生的显著影响。GO 数据表明，大多数差异表达基因参与结合、催化活性以及代谢和细胞过程。此外，结果表明，抗菌肽如 gloverin、cecropin E 和溶菌酶的转录水平在寄生后上调。在寄生幼虫中检测到了姬病毒基因的表达，从五个 PDV 基因家族中鉴定出了 19 个独特的序列，包括 vankyrin、病毒连接蛋白、重复元件、富含半胱氨酸的基序和富含极性残基的蛋白。在 DsIV 基因中，vankyrin 1 和重复元件 1 基因的转录水平最高。
本研究提供了小菜蛾幼虫寄生后基因差异表达的详细信息、宿主中表达的 DsIV 基因，并提高了我们对这种宿主-寄生蜂相互作用的认识。
