Submitted to: Entomological Research Bulletin of
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/4/2005
Publication Date: 4/1/2006
Citation: Oppert, B.S., Walters, P., Zuercher, M.C. 2006. Digestive proteinases of the larger black flour beetle, Cynaeus angustus (Leconte) (Coleoptera: Tenebrionidae). Bulletin of Entomological Research 96: 167-172. Interpretive Summary: The larger black flour beetle is a pest of stored grains and grain products. We studied digestion in the larger black flour beetle to identify new control methods. We found digestive enzymes from several different enzyme classes in larger black flour beetle larvae, which may explain the diversity in their food choices. The results indicate that control of the larger black flour beetle may be improved if cereals are altered to express higher levels of multiple inhibitors of digestive enzymes.
Technical Abstract: Digestion in the larger black flour beetle, Cynaeus angustus (LeConte), was studied to identify new control methods for this pest of stored grains and grain products. The physiological pH of the larval gut, as measured with extracts in water, was approximately 6.1, and the pH for optimal hydrolysis of casein by gut extracts was 6.2 when buffers were reducing. However, under nonreducing conditions, hydrolysis of casein and synthetic serine proteinase substrates was optimal in alkaline buffer. Three major proteinase activities were observed in zymograms using casein or gelatin. Caseinolytic activity of C. angustus gut extracts was inhibited by inhibitors that target aspartic and serine proteinase classes, with minor inhibition by a cysteine proteinase inhibitor. In particular, soybean trypsin and trypsin/chymotrypsin inhibitors were most effective in reducing the in vitro caseinolytic activity of gut extracts. Therefore, genes encoding soybean inhibitors of serine proteinases warrant further studies as candidates for transgenic grains with increased resistance to damage by C. angustus.