Submitted to: PeerJ
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/2015
Publication Date: 1/18/2016
Publication URL: http://handle.nal.usda.gov/10113/62118
Citation: Perkin, L.C., Elpidina, E.N., Oppert, B.S. 2016. Expression patterns of cysteine peptidase genes across the Tribolium castaneum life cycle provide clues to biological function. PeerJ. 4:e1581. doi: 10.7717/peerj.1581.
Interpretive Summary: The red flour beetle is a major stored product pest responsible for great economic loss worldwide. The red flour beetle has a specialized gut, arranged to efficiently breakdown grain and cereal products. Our previous work has shown there is a group of 25 closely related genes called cysteine proteases that potentially have a role in digestion. We know that two of them are in high abundance in the larval midgut and seven of them increase when larvae are fed protease inhibitors. In the present study, we used RNA-seq to quantify the expression of all 25 genes across the four major life stages of the red flour beetle (egg, larvae, pupae, and adult). We hypothesized that cysteine proteases used by the beetle for digestion would have high expression in feeding stages (adult and larvae), but not in other stages (egg and pupae). We identified 12 genes with this expression pattern. Combining this data to existing data we made a new model categorizing each gene as either digestive or not digestive. We conclude that eight genes have a major role in digestion in the red flour beetle. This information adds to the body of literature on the beetle gut as well as contributes to the development of new pest control products and strategies.
Technical Abstract: The red flour beetle, Tribolium castaneum, is a major agricultural pest responsible for considerable loss of stored grain and cereal products worldwide. T. castaneum larvae have a highly compartmentalized gut, with cysteine peptidases mostly in the acidic anterior part of the midgut. We have described 26 putative cysteine peptidase genes in T. castaneum (types B, L, O, F, and K) located mostly on chromosomes 3, 7, 8, and 10. In the present study, we hypothesized that we could associate specific cysteine peptidase genes with digestive functions for food processing based on comparison of gene expression profiles in different developmental stages, feeding and nonfeeding. We used RNA-Seq to determine the relative expression of cysteine peptidase genes among four major developmental stages (egg, larvae, pupae, and adult) of T. castaneum. We also compared T. castaneum cysteine peptidase genes to those in other model insects and coleopteran pests. By combining transcriptome expression, phylogenetic comparisons, response to inhibitors, and other existing data we made predictions of key cysteine peptidases used for food digestion in T. castaneum. This data contributes new information on digestion in an agricultural pest and will be helpful in developing targeted pest control strategies for tenebrionid insects.