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Title: A New Gut-Specific Chitinase Gene Essential for Regulation of Chitin Content of Peritrophic Matrix and Growth of Ostrinia Nubilalis Larvae

item KHAJURIA, CHITVAN - Kansas State University
item BUSCHMAN, LARRY - Kansas State University
item Chen, Ming-Shun
item MUTHUKRISHNAN, SUBBARATNAM - Kansas State University
item ZHU, KUN YAN - Kansas State University

Submitted to: Insect Biochemistry and Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/11/2009
Publication Date: 8/1/2010
Citation: Khajuria, C., Buschman, L.L., Chen, M., Muthukrishnan, S., Zhu, K. 2010. A New Gut-Specific Chitinase Gene Essential for Regulation of Chitin Content of Peritrophic Matrix and Growth of Ostrinia Nubilalis Larvae. Insect Biochemistry and Molecular Biology. 40:621-629.

Interpretive Summary: Chitin is an important structural component of the insect cuticle. For insects to grow and change from one developmental stage to another, chitin in the cuticle and the peritrophic matrix needs to be digested and replaced with new chitin. Therefore, the metabolic pathways of chitin in insects are targets for insecticides for use in pest management. This research has led to the identification of a new gut-specific chitinase gene from the larvae of European corn borer, an important insect of corn. The gut-specific chitinase plays an important role in regulating the chitin content of the peritrophic matrix and it effects the growth and development of European corn borer larvae. The identification of this new chitinase provides a foundation for further research that may lead to practical applications and to a better understanding of chitin content regulation in insects.

Technical Abstract: Chitinases belong to a large and diverse family of hydrolytic enzymes that break down glycosidic bonds of chitin. However, very little is known about the function of chitinase genes in regulating the chitin content in peritrophic matrix (PM) of the midgut in insects. We identified a cDNA putatively encoding a new chitinase (OnCht) in European corn borer (ECB; Ostrinia nubilalis). The OnCht gene was predominately expressed in larval midgut with no detectable expression in eggs, pupae, or adults. When the larvae were fed an artificial diet, the expression of OnCht increased 4.4-fold but the expression of the gut-specific chitin synthase (OnCHS 2) gene decreased 2.5-fold as compared with those of unfed larvae. In contrast, when larvae were fed and then starved for 24h, the expression of OnCht decreased 1.8-fold but the expression of OnCHS-2 increased 1.8-fold. Furthermore, there was a negative relationship between OnCht gene expression and chitin contents in the midgut. By using a feeding-based RNAi technique, we were able to reduce OnCht transcript level about 63% in the larvae. Consequently, these larvae showed significantly increased chitin content (26%) in the PM but decreased larval body weight (54 %) as compared with control larvae fed on the diet containing GFP dsRNA. We provide strong evidence for the first time that OnCht plays an important role in regulating chitin content of the PM and it effects the growth and development of the ECB larvae.