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Title: Analysis of functions of the chitin deacetylase gene family in Tribolium castaneum

Author
item ARAKANE, YASUYUKI - KANSAS STATE UNIVERSITY
item BEGUM, KHURSHIDA - KANSAS STATE UNIVERSITY
item DIXIT, RADHIKA - KANSAS STATE UNIVERSITY
item PARK, YOONSEONG - KANSAS STATE UNIVERSITY
item SPECHT, CHARLES - UNIV MASSACHUSETTS
item KRAMER, KARL - 5430-05-30 RETIRED
item MUTHUKRISHNAN, SUBBARATNAM - KANSAS STATE UNIVERSITY
item Beeman, Richard

Submitted to: Insect Biochemistry and Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2009
Publication Date: 6/1/2009
Citation: Arakane, Y., Begum, K., Dixit, R., Park, Y., Specht, C.A., Kramer, K.J., Muthukrishnan, S., Beeman, R.W. 2009. Analysis of Functions of the Chitin Deacetylase Gene Family in Tribolium castaneum. Insect Biochemistry and Molecular Biology 39: 355-365.

Interpretive Summary: Insects must shed their old skins as they grow in size, but the behavior and physiology of this delicate and complex process of metamorphosis is still only poorly understood. We identified a group of “chitin-trimming” enzymes in flour beetles that are needed to confer the proper degree of stiffness or flexibility on the raw chitin, and we showed that inactivation of these enzymes results in defects in the chitinous exoskeleton. Each of these newly-discovered enzymes represents a potential target in screening assays for new biopesticides that disrupt insect growth and development.

Technical Abstract: The expression profiles of nine genes encoding chitin deacetylase (CDA)-like proteins were studied during development and in various tissues of the red flour beetle, Tribolium castaneum, by RT-PCR. TcCDA1, TcCDA2 and TcCDA5 were expressed throughout all stages of development, while TcCDA6 – 9 were expressed predominantly during larval feeding stages. In situ hybridization experiments revealed that both TcCDA1 and TcCDA2 were expressed in epidermal cells. TcCDA6 through TcCDA9, which belong to a distinct subgroup of gut-specific CDAs, were expressed in the cells lining the midgut, including epithelial cells. TcCDA3 was expressed in the thoracic muscles, whereas TcCDA4 was expressed in early imaginal appendages. To study the function(s) of individual TcCDA genes, double-stranded RNAs (dsRNA) specific for each gene were injected into insects at different developmental stages and the phenotypes were monitored. No visible phenotypic changes were observed after injection of dsRNAs for TcCDA3 to 9, whereas injection of dsRNAs for TcCDA1 or TcCDA2 affected all types of molts, including larval-larval, larval-pupal and pupal-adult. Insects treated with these dsRNAs could not shed the old cuticle and were trapped in their exuviae. Interestingly, unique and very dissimilar adult phenotypes were observed after injection of dsRNAs that specifically down-regulated either of the two alternatively spliced transcripts of TcCDA2, namely TcCDA2a or TcCDA2b. These results reveal functional specialization among Tribolium CDA genes and splice variants.