Characterization of the transcriptome and the peptidase and the non-peptidase homologs of callosobruchus maculatus

Abstract

The cowpea bruchid, Callosobruchus maculatus is a major pest of the cowpea, which is an important crop in many areas of Africa and is also consumed in other parts of the world. The cowpea utilizes serine peptidase inhibitors as a defense against herbivorous insects. Peptidases have been considered a target for pest control. The cowpea bruchid in turn employs cysteine peptidases as its major digestive peptidase to avoid the plant’s defense. Important not only in digestion, but in other functions such as immune response and molting, the peptidase and non-peptidase homologs were annotated. Here a de novo transcriptome assembly was built from 840,766 Roche 454 reads using CLC Genomics workbench. The assembly resulted in 35,111 contigs that were analyzed using Blast2GO. Important not only in digestion, but in other functions such as immune response and molting, the peptidase and non-peptidase homologs were annotated. A local BLAST search against sequences downloaded from the MEROPS database found 264 putative peptidase and non-peptidase homologs for C. maculatus. Illumina sequencing from the same sample produced 295,690,882 reads which were mapped back to the assembly using BWA software. While C. maculatus does not appear to have an increased number of cysteine peptidases compared with other insects it does appear have more highly expressed cysteine peptidases compared to serine peptidases. Examination of the peptidase and non-peptidase homolog composition of C. maculatus might ultimately lead to innovations in pest management or other biological insights.