Cellulase gene expression profiles in termites according to different habitats and diets

To investigate the cellulase gene profiles in termites according to different habitats and diets, we collected two species (Schedorhinotermes spp. and Macrotermes spp.) from the rotten damp wood, one species (Microtermes spp.) from the dry wood and one species (Microtermes spp.) from the cow dung. Total RNA was extracted respectively from the hind gut containing paunch and from other remaining tissues, and used for the suppression subtractive hybridization to enrich cellulase genes. The resulting EST libraries were sequenced, the cellulase genes were identified by BLAST search, and their phylogenetic relationships were determined. Depending on the diet, termites exhibited different expression profiles of cellulase gene. The endo-beta-1,4-glucanase was determined to be the predominant cellulase only in the termite species consuming dry wood. In contrast, the termite species consuming rotten damp wood (Schedorhinotermes spp. and Macrotermes spp.) possessed the glycoside hydrolase family 7, which is categorized into the exocellulase group, as the major cellulase. Likewise, beta-glucosidase, another exocellulase family, was found as the major cellulase in the termite species consuming cow dung (Microtermes spp.). Based on our findings, it can be hypothesized that since raw cellulose materials are likely preprocessed by cellulolytic microorganisms in the damp wood or cow dung, termites consuming the diet materials of preprocessed cellulose (i.e., cellobiose) appears to have adapted to produce more exocellulases than endocellulases. This notion was supported by the fact that endo-beta-1,4-glucanase (i.e., endocellulase) was predominantly expressed only in Microtermes spp. termite consuming the raw cellulose of dry wood.