Cross-species comparison of the gut: Differential gene expression sheds light on biological differences in closely related tenebrionids

Authors: Oppert, Brenda; Perkin, Lindsey; MARTYNOV, ALEXANDER - Moscow State University; ELPIDINA, ELENA - Moscow State University

Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/24/2017
Publication Date: N/A
Citation: N/A

Interpretive Summary: The gut is one of the primary interfaces between an insect and its environment, so understanding how genes are expressed in the insect gut can provide insight into how insects interact with the environment as well as identify potential control targets for pests. We identified genes that are common in the gut of larvae of two darkling beetles, the yellow mealworm and the red flour beetle, but there were differences in the expression of these genes. In the red flour beetle genes associated with energy production and food digestion were overrepresented, but in the yellow mealworm genes associated with lipid binding were overexpressed. There were ~3,000 genes in each beetle species that were unique to that species. It was remarkable that reads from the larval gut of red flour beetle and yellow mealworm mapped to 910 and 798 genes, respectively, with unknown function. The data suggest that in addition to the need for more sequenced insect genomes, the functions of many genes are needed in order to fully understand important systems such as digestion and metabolism in insects. These data provide more information about the gut of these beetles and genes that have enabled adaptation to food sources and environment. Continuing efforts to obtain additional data in these insects as well as other beetle pests will contribute to our understanding of the evolution of beetles and their success as specialist and/or generalist feeders.

Technical Abstract: The gut is one of the primary interfaces between an insect and its environment. Understanding gene expression profiles in the insect gut can provide insight into interactions with the environment as well as identify potential control methods for pests. We compared the gut expression profiles of larval stages of two coleopteran insects, Tenebrio molitor and Tribolium castaneum. Although these insects are both tenebrionids, they have different life cycles, varying in the duration and number of larval instars. T. castaneum has a sequenced genome, and microarray data that also provided relative expression data for gut transcripts. T. molitor lacks a sequenced genome and there is little genomic data available for this insect. We assembled gut transcriptome reads from both insects to the arthropod RefSeq dataset, and contigs without hits were annotated through Blast2GO. From these datasets, we compiled an ortholog list of 4,236 genes, with GO functions of catalytic activity, as well as metabolic and cellular processes, prominent among the ortholog gene set. Ten percent of the total assembled reads were found in 20 genes in both insects, although these genes were different for each insect. There were 2,681 genes unique to T. castaneum, and 3,060 genes unique to T. molitor, although there are likely additional orthologs in these datasets that will be identified through further sequencing. Contigs with no hits to any database included 1,286 and 5,114 in T. castaneum and T. molitor, respectively, and the large number of assembled reads in some of the contigs suggest that additional genes may be discovered in these species. These data are the first step in building a comprehensive understanding of digestion and immunity in tenebrionid insects, illustrating commonalities and differences that may be related to speciation and environmental adaptation.