Skip to main content
ARS Home » Research » Publications at this Location » Publication #172754
Title: THE TRIBOLIUM CHITIN SYNTHASE GENES TCCHS1 AND TCCHS2 ARE SPECIALIZED FOR SYNTHESIS OF EPIDERMAL CUTICLE AND MIDGUT PERITROPHIC MATRIX

Author
item ARAKANE, YASUYUKI - KANSAS STATE UNIV
item MUTHUKRISHNAN, SUBBARATNAM - KANSAS STATE UNIV
item KRAMER, KARL - RETIRED 5430-05-30
item SPECHT, CHARLES - BOSTON UNIVERSITY
item TOMOYASU, YOSHINORI - KANSAS STATE UNIV
item Lorenzen, Marce
item KANOST, MICHAEL - KANSAS STATE UNIV
item Beeman, Richard

Submitted to: Insect Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2005
Publication Date: 9/30/2005
Citation: Arakane, Y., Muthukrishnan, S., Kramer, K.J., Specht, C.A., Tomoyasu, Y., Lorenzen, M.D., Kanost, M., Beeman, R.W. 2005. The Tribolium chitin synthase genes TcCHS1 and TcCHS2 are specialized for synthesis of epidermal cuticle and midgut peritrophic matrix. Insect Molecular Biology 14: 453-463.

Interpretive Summary: Chitin is the main component of the cuticle which forms a protective outer covering of insects. The biosynthesis of chitin is a critical and precisely regulated step during insect molting but there is very little evidence about the different functions of the two enzymes which produce this critically important biomaterial in insects. We used a technique called "RNA interference" to selectively eliminate the function of each of the two genes that produce these enzymes in the red flour beetle to see if different parts of the insect were affected differently. We showed that one of the genes is required for producing the chitin that covers the general body surface, while the other is required for producing the chitin that lines the digestive midgut. Without the first gene, the insects cannot shed their old skins and therefore die of entanglement in the old cuticle. Without the second gene, the insects cannot digest food, and die of starvation. Studies such as these will lead to better understanding of insect growth and development and better strategies for disrupting the associated genes for pest control.

Technical Abstract: Functional analysis of the two chitin synthase genes, TcCHS1 and TcCHS2, in the red flour beetle, Tribolium castaneum, revealed unique and complementary roles for each gene. TcCHS1-specific RNA interference (RNAi) disrupted all three types of molt, larval-larval, larval-pupal and pupal-adult, and greatly reduced whole-body chitin content. Exon-specific RNAi showed that splice variant 8a of TcCHS1 was required for both the larval-pupal and pupal-adult molts, whereas splice variant 8b was required only for the latter. TcCHS2-specific RNAi had no effect on metamorphosis or on total body chitin content. However, RNAi-mediated down-regulation of TcCHS2, but not TcCHS1, led to cessation of feeding, a dramatic shrinkage in larval size, and reduced chitin content in the midgut. These results provide direct evidence that TcCHS1 contributes to synthesis of chitin in the insect's epidermis for cuticle formation, whereas TcCHS2 is utilized for synthesis of chitin in the midgut epithelium for formation of the peritrophic membrane.