A reference transcriptome from all developmental stages of the cowpea bruchid, Callosobruchus maculatus (Coleoptera: Chrysomelidae): Annotation of peptidase and immune-related genes.

The cowpea bruchid, Callosobruchus maculatus is common pest of stored leguminous seeds. Particularly, it is a major pest of stored cowpea grain in many areas of Africa, where these harvested grains constitute a major dietary source of protein for people in developing nations. Insect C1 cysteine protease inhibition and immune response is important in this plant(seed)-insect interaction. A reference transcriptome of 35,118 contigs was de novo assembled from a pooled cDNA library from all life stages sequenced by Roche 454 Titanium technology. Gene annotation and ontology predictions identified 269 putative peptidase and non-peptidase C. maculatus homologs, the latter class lacking predicted proteolytic activity due mutation in one or more catalytic residues. Of the 62 predicted C. maculatus C1-cysteine peptidase family members, 21 were novel (12 cathepsin L; 6 cathepsin B, and the remaining 3 in the following classes: cathepsin O, cathepsin F and bleomycin hydrolase). Gene annotation of the C. maculatus transcript assembly also predicted orthologues for the three major intracellular immune pathways; Toll, Immune-deficiency (IMD), and Janus Kinase and Signal Transducer and Activator of Transcription (JAK/STAT). Four putative CLIP domain serine proteinases and 16 serpin-like serine protease inhibitors involved in Toll and IMD regulation were identified. The C. maculatus reference transcriptome and predicted peptidase and immune-defense proteins coding genes provide critical tools for the evaluation of current and future pest management tactics, and provide baseline information for subsequent functional genomic studies of plant insect interactions.