Pyrosequencing of the midgut transcriptome of the poplar leaf beetle Chrysomela tremulae reveals new gene families in Coleoptera

Abstract

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 of defining 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 gene families involved in plant tissue digestion, which have no homologs in the genome of the stored product pest the Red Flour beetle, Tribolium castaneum.

Transcriptome analysis of the salivary glands of potato leafhopper, Empoasca fabae

“…However, a portion of the sequences showed similarity to other eukaryotes (12%), bacteria (4%), fungi (0.4%) and virus (0.3%) as observed in other insect transcriptomic studies ( Fig. 2; Table S3) (Pauchet et al, 2009;Mittapalli et al, 2010).…”

“…Roche Ò 454 pyrosequencing has in the recent past revolutionized functional genomic studies in non-model organisms, particularly in insects wherein little to no genetic information is available (Francischetti et al, 2007;Morozova and Marra, 2008;Margulies et al, 2005;Vera et al, 2008;Pauchet et al, 2009;Mittapalli et al, 2010;Bai et al, 2011). The developed transcriptomic database can subsequently be used as a reference for future functional studies like RNA seq and to mine for candidate targets for RNAi experiments.…”

Field-evolved resistance by western corn rootworm to multipleBacillus thuringiensistoxins in transgenic maize

“…The structural similarity among three-domain toxins suggests potential similarities in binding sites in the insect midgut, whereas competitive binding analysis with Cry34/35Ab1 and mCry3A indicates at least some discordance in binding sites (21,22). Proteins in the insect midgut involved with the mode of action for three-domain Bt toxins include alkaline phosphatase, aminopeptidase, and cadherin, and these proteins have been isolated from the midgut of the Chrysomelidae, the family of which western corn rootworm is a member (23,24). Thus, alteration of certain Bt-binding sites may confer resistance to Cry3Bb1 and mCry3A simultaneously while not affecting susceptibility to Cry34/35Ab1.…”

The transcriptome of Spodoptera exigua larvae exposed to different types of microbes

“…Genes involved in the different mechanisms are relatively well characterized in the model organism Drosophila melanogaster, although very little is known for nonmodel organisms. Only recently, because of the generalization of the NGS technologies, are pathogen-related genes being identified in non-model insects (Pauchet et al, 2009;Mittapalli et al, 2010;Bai et al, 2011).…”