Chrysomela tremulae larval midgut
Pyrosequencing of the midgut transcriptome of the poplar leaf beetle Chrysomela tremulae reveals new gene families in Coleoptera
The insect midgut is the primary target site for Bt-derived insecticides and Bt alternatives. However,  despite extensive recent study, the precise role and nature of different Bt receptors remains a subject of  considerable debate. This problem is fuelled by a lack of understanding of the genes expressed in the  insect midgut and their physiological roles. The poplar leaf beetle, Chrysomela tremulae, is an important  model for understanding the mode of action of, and resistance to, coleopteran-specific Bt toxins and  currently shows the only known naturally occurring case of resistance to Cry3A toxins. Moreover it  belongs to the same family as the corn rootworm, Diabrotica virgifera, an economically important beetle  pest and target of hybrid corn expressing Cry3 toxins. Pyrosequencing is a fast and efficient way ofdefining the transcriptome of specific insect tissues such as the larval midgut. Here we use 454 based pyrosequencing to sample the larval midgut transcriptome of C. tremulae. We identify candidate genes of putative Bt receptors including transcripts encoding cadherin-like proteins, aminopeptidase N and alkaline phosphatase. We also describe a wealth of new transcripts predicting rapidly evolving families involved in plant tissue digestion, which have no homologs in the genome of the stored pest the Red Flour beetle, Tribolium castaneum.