ARS | Publication request: Characterization of four esterase genes and esterase activity from the gut of the termite Reticulitermes flavipes

Submitted to: Archives of Insect Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 15, 2009
Publication Date: January 1, 2010
Citation: Wheeler, M.M., Tarver, M.R., Coy, M.R., Scharf, M.E. 2010. Characterization of four esterase genes and esterase activity from the gut of the termite Reticulitermes flavipes. Archives of Insect Biochemistry and Physiology. 73(1):30-48.

Interpretive Summary: Wood is the primary source of nutrition for termites, which possess a battery of enzymes which can break down this complex substance while other organisms cannot. A group of these enzymes, the esterases, were discovered in the gut of the eastern subterranean termite, Reticulitermes flavipes. This work sought to identify and characterize the genes encoding these enzymes, to determine if they were expressed by the termites themselves or by their bacterial symbionts, to determine the location of their expression within the termite, and to determine the enzymatic activity of these enzymes to known substrates for esterases.

Technical Abstract: Four esterase genes and general esterase activity were investigated in the gut of the termite Reticulitermes flavipes. Two genes (RfEst1 and RfEst2) share significant translated identity with a number of insect JH esterases. The two remaining genes (RfEst3 and RfEst4) apparently code for much shorter proteins with similarity to fungal phenolic acid esterases involved in hemicellulose solubilization. All four genes showed consistently high midgut expression. This result was further supported by colorimetric activity assays and Native polyacrylamide gel electrophoresis, which showed significant esterase activity and a number of isoforms in the midgut. The greatest esterase activity and isoform composition were detected when a-naphthyl propionate was used as a substrate. Moreover, esterase activity and diverse isoforms were present in gut mitochondrial, microsomal, and cytosolic sub-cellular protein fractions, as well as in the hindgut lumen. These findings reveal an agreement between gut esterase gene expression and activity distributions, and support the idea that R. flavipes gut esterase activity is host (not symbiont)-derived. In addition, these findings support the hypotheses that termite gut esterases may play important roles in lignocellulose digestion and caste differentiation. This study provides important baseline data that will assist ongoing functional-genomic efforts to identify novel genes with roles in semiochemical, hormone, and lignocellulose processing in the termite gut.