Submitted to: Insect Biochemistry and Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/21/2013
Publication Date: 6/4/2013
Publication URL: http://www.sciencedirect.com/science/article/pii/S0965174813001008
Citation: Chen, H., Zhu, Y., Whitworth, J.R., Reese, J.C., Chen, M. 2013. Serine and cysteine protease-like genes in the genome of a gall midge and their interactions with host plant genotypes. Insect Biochemistry and Molecular Biology. 43: 701-711. Interpretive Summary: Hessian fly is a major insect pest of wheat. The insect is mainly controlled through host plant resistance. Therefore, understanding the mechanisms of wheat defense against Hessian fly may provide useful information to improve wheat resistance to Hessian fly. One potential target for plant defense against insects is the digestive enzymes, particularly proteases, in the insect gut. This research took advantage of the availability of the Hessian fly genome sequence and systematically analyzed the composition and expression of all digestive proteases in the Hessian fly larval gut. Major putative digestive trypsins, chymotrypsins, and cysteine proteases were identified and their expression profiles among tissues and different developmental stages were determined. The study should provide a foundation for future research for utilization of plant protease inhibitors for management of this insect pest.
Technical Abstract: For plant-feeding insects, digestive proteases are targets for engineering protease inhibitors for pest control. In this study, we identified 105 putative serine- and cysteine-protease genes from Hessian fly genome. Among the genes, 31 encode putative trypsins, 18 encode putative chymotrypsins, seven encode putative cysteine proteases, and the remaining may encode either other proteases or protease homologues. Developmental stage- and tissue-specific expression profiles of the genes encoding putative trypsins, chymotrypsins, and cysteine proteases were determined by quantitative reverse-transcription PCR. Comparative analyses of stage- and tissue-specific expression patterns suggested that the following genes are likely to encode digestive proteases in the M. destructor larval gut, including genes encoding putative trypsins MDP3, MDP5, MDP9, MDP24, MDP48, MDP51, MDP57, MDP61, MDP71, and MDP90; genes encoding putative chymotrypsins MDP1, MDP7, MDP8, MDP18, MDP19, MDP20, MDP21, and MDP22; and genes encoding putative cysteine proteases MDP95 and MDP104. The expression of some protease genes was affected by plant genotypes. Genes encoding trypsins MDP3, MDP9, and MPD23, chymotrypsins MDP20 and MDP21, and cysteine proteases MDP99 and MDP104 were upregulated in M. destructor larvae feeding in resistant plants, whereas genes encoding trypsins MDP12, MDP24, and MDP33, and chymotrypsins MDP8, MDP15, and MDP16 were downregualted in M. destructor larvae feeding in resistant plants. This study provides a foundation for further comparative studies on proteases in different insects, and further characterization of M. destructor digestive proteases and their interactions with host plants, as well as potential targets for transgenic wheat plants.