What the midgut transcriptome tells us about the stored product pest Callosobruchus maculatus, the cowpea weevil

The cowpea weevil Callosobruchus maculatus is a pervasive stored product pest of cowpeas (Vigna unguiculata) . Cowpeas are a key protein rich crop in the semi arid tropics of the world. Post harvest losses have a large impact on subsistence farmers who rely on cowpeas for both protein and income. Once the cowpea larva hatches from the egg, which is attached to the seed, it tunnels its way into the seed where it will complete all of its molts before emerging as an adult. Coleoptera is one the most speciose orders on the planet and yet the only sequenced beetle genome is that of Tribolium castaneum, limiting the use of genomic approaches for studying and managing colepteran pests. Creating a reference transcriptome is a simpler and more cost effective way to examine the genes of organism. However, compiling RNA-seq transcriptome data without a reference genome poses challenges since short reads are difficult to align into functional contigs. For this study RNA was extracted from whole insects of all life stages and both Illumina and 454 reads were used to create a de novo assembly. In order to overcome the challenge of working without a reference genome the de novo assembly was created using an iterative, varied kmer approach to obtain functional contigs. The program Blast2GO was used to obtain the BLAST and gene ontology results of the contigs.