Transcriptomics of the diamondback moth, Plutella xylostella

Adaptation to insecticides has made the diamondback moth, Plutella xylostella (L.), an important pest worldwide, but molecular resources remain limited for studying the mechanisms involved. We adopted transcriptome sequencing via the 454 platform, in an effort to further genomic studies in P. xylostella, especially those relating to physiological tolerance and behavioral avoidance of insecticides. More than 198,000 reads from a quarter of a picotiterplate run produced 61,058 unigenes (contigs and singletons that weren’t assembled). Homology searches on unigenes against nonredundant protein databases and comparison with the genome of 3 model insect species were performed. The assembled sequences were also annotated with gene ontology terms, gene names, and conserved protein families and domains. More than 5,900 of the unigenes were annotated and targeted searches using the annotations predicted a number of cytochrome P450s (P450s) and glutathione S-transferases (GSTs), a voltage-gated sodium channel and BCS1, which is an orthologue of another insect sodium channel known as DSC1. In addition, sequences encoding chemosensory proteins (CSPs), odorant receptors (Or), a general odorant binding protein (GOBP), an antennal binding protein (ABP), a gustatory (Gr) and ionotropic glutamate receptors (iGluRs) were discovered in the EST dataset. Putative domains for RNAi components such as SID-1 PIWI and dsRNA binding proteins were also detected. The unigenes set in this study provides additional sequence resources to those currently available for P. xylostella and will enable more detailed research into the biological processes and mechanisms underlying its success in adapting to insecticides.