Cloning and Expression Profiling of Cuticular Protein Genes of Spodoptera litura

[Objective] The expression pattern of fourteen cuticular protein (CP) genes (ICPG) in Spodoptera litura were analyzed in this study, which provided reference for further study on the function of cuticular proteins in the growth and development of S. litura. [Method] Polymerase chain reaction (PCR) was used to amplify the cDNAs of the genes encoding CPs of S. litura. Their nucleotide sequences and corresponding amino acid sequences were analyzed, and lepidopteran phylogenetic tree was constructed using MEGA5.2 software. The expression of CP genes was analyzed in the third to the sixth instar larvae and 2-day-old adult genital organs by the reverse transcription PCR (RT-PCR) technique. [Result] Fourteen cDNAs coding 14 CPs of S. litura were obtained. The sequence analysis showed 14 CPs harbor the conserved motif of 35－36 amino acids that is a typical feature of chitin-binding proteins and share high sequence homology with CPs of Helicoverpa armigera. RT-PCR results showed that these CP genes were expressed in the third to the sixth instar larvae and 2-day-old adults. In particular, their relative expression levels are higher in the cuticulars of older larvae and lower in the fat bodies of younger larvae. In addition, the relative expression of 14 CP genes was low in testes and ovaries. The highest relative expression of SlICPG-11 and SlICPG-14 in the pupal stage. [Conclusion] In this study, the cDNA of 14 S. litura CP genes were cloned. Their expression exhibited tissue and developmental stage specificity indicating their putative roles in S. litura development. It lays the foundation for target site selection for the control of S. litura.