title: Deep sequencing-based transcriptome analysis of Plutella xylostella larvae parasitized by Diadegma semiclausum.
abstract: BACKGROUND
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors: School of Biological Sciences, The University of Queensland, St Lucia QLD 4072 Australia.
authors: Kayvan
authors: K
authors: Etebari
authors: Robin W
authors: RW
authors: Palfreyman
authors: David
authors: D
authors: Schlipalius
authors: Lars K
authors: LK
authors: Nielsen
authors: Richard V
authors: RV
authors: Glatz
authors: Sassan
authors: S
authors: Asgari
mesh_terms: D000818:Animals; D020869:Gene Expression Profiling; D017344:Genes, Insect; D059014:High-Throughput Nucleotide Sequencing / Q000379:methods; D006790:Host-Parasite Interactions / Q000235:genetics*; D007814:Larva / Q000235:genetics / Q000469:parasitology / Q000821:virology; D009036:Moths / Q000235:genetics* / Q000469:parasitology* / Q000821:virology; D018071:Polydnaviridae / Q000235:genetics*; D017422:Sequence Analysis, DNA / Q000379:methods; D059467:Transcriptome; D014863:Wasps / Q000502:physiology* / Q000821:virology