Submitted to: Journal of Proteome Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2011
Publication Date: 1/15/2012
Citation: Dittmer, N.T., Hiromasa, Y., Tomich, J.M., Lu, N., Beeman, R.W., Kramer, K.J., Kanost, M.R. 2012. Proteomic and transcriptomic analyses of rigid and membranous cuticles and epidermis from the elytra and hindwings of the red flour beetle, Tribolium castaneum. Journal of Proteome Research. 11(1): 269-278. http://dx.doi.org/ 10.1021/pr2009803. Interpretive Summary: The insect exoskeleton has many functions vital for insect survival, and is therefore an attractive target for new biopesticide design. Among the most important functions of beetle exoskeleton are to confer lightweight flexibility to the flight wings, or strength and rigidity to the nonflight wing covers, to either enable flight or confer protection. We identified more than 100 proteins in beetle wings and wing covers, including many that appear to affect the physical properties of exoskeleton. Some of these were predominantly found in wings, and others in wing covers. Each of these two groups had distinct biochemical fingerprints, which probably reflect their different functions in flexible vs rigid tissues. Understanding the biochemical basis of the properties and functions of insect exoskeleton will aid our continuing efforts to reveal new weaknesses that may lead to new methods of insect control.
Technical Abstract: The insect cuticle is a remarkable composite biomaterial made up primarily of chitin and proteins. The physical properties of the cuticle can vary greatly in different regions. Cuticle that is hard and rigid offers support for internal organs and protection from environmental stresses. Cuticle that is soft and flexible allows for ease of movement. Understanding how different cuticle types are assembled can aid in the development of novel biomimetic materials for use in medicine and technology. Towards this goal we have taken a combined proteomics and transcriptomics approach with the red flour beetle, Tribolium castaneum, to examine the protein and gene expression profiles of the elytra and hindwings, examples of rigid and soft cuticles, respectively, with an emphasis on cuticular structural proteins and their corresponding genes. We identified 118 proteins by 2D gel electrophoresis and MALDI/TOF mass spectroscopy, of which 52 were predicted to be secreted. Nineteen of the 52 were homologous to known or hypothesized cuticular proteins (CPs), with the majority belonging to the Rebers and Riddiford (CPR) family. Electrophoretic analysis revealed distinct differences in the protein profiles between elytra and hindwings. Four highly abundant proteins dominated the elytral cuticle extract, including three CPR proteins and a novel, low complexity protein enriched in glutamic acid, arginine, and histidine. Microarray analysis identified 372 genes that showed a 10-fold or greater difference in transcript levels between elytra and hindwings: 296 had higher expression in elytra and 76 had higher expression in hindwings. Significantly, CP gene families tended to be preferentially expressed in one or the other structure. Those in the elytra were classified as either CPR type 2, or cuticular proteins of low complexity (CPLC) enriched in glycine or proline. A majority of the CP genes with higher expression in hindwings were classified as CPR type 1, cuticular proteins analogous to peritrophins (CPAP), or members of the Tweedle family. Our analysis may lead to a better understanding of the effects of protein composition on the construction and physical properties of cuticle.