Transcriptome analysis and screening for potential target genes for RNAi-mediated pest control of corn earworm, Helicoverpa zea

The corn earworm, Helicoverpa zea is a serious pest worldwide that caused significant demages each year. Unfornately the accessable genetic resource of this insect is quite limited. To improve this situation, we sequenced the late embryo stage and newly hatched neonates transcriptome of Helicoverpa zea using the Illumina Solexa platform. We assembled the transcriptome with Trinity that yielded 161,414 contigs. Of these contigs, 68,592 were annotated as protein coding genes by Blast searches against the NCBI nr database. It has been proved that RNAi can be a new technology for pest management by removing, or silencing, specific fatal genes in insects. Therefore, the first key step towards developing an efficient RNAi-mediated pest control technique is to find suitable target genes. To screen for effective target genes in the corn earworm, we selected eight candidate genes. The dsRNAs were designed by the RNA-Seq data. We used different methods to test the efficiency of RNAi in this insect, the mRNA abundance of target genes decreased to different levels after inducing dsRNA in their body. Knockdown of ache1, chitinase1, tipE caused a significant mrotality effect compared to the negative (P<0.05). Thus, our transcriptome data could be a valuable genetic resource for identification of genes in Helicoverpa zea and provided a successful method for RNAi pest control in this pest.