Xuguo Zhou, Joseph A. Smith, Faith M. Oi, Phillip G. Koehler, and Michael E. Scharf. Entomology & Nematology, University of Florida, PO Box 110620, Gainesville, FL 32611-0620
Termites have developed unique cellulose digestion capabilities that allow them to obtain energy and nutrition from recalcitrant food sources, such as lignocellulosic plant material (e.g. wood) or residues derived from it (e.g. humus). Lower termites, which are equipped with both endogenous and symbiotic cellulases, feed primarily on wood and wood-related products. Here, we investigated cellulase gene diversity, structure, and function in the lower termite, Reticulitermes flavipes (Kollar). We identified four genes encoding one endogenous and three symbiotic cellulases, herein referred to as Cell-1, -2, -3 and -4. These four genes encode proteins with significant homology to endoglucanases, exoglucanases and xylanases. Gene structure studies on Cell-2 revealed the first intron sequence from a termite symbiont, and one of the first introns ever sequenced from a protozoan. Quantitative real-time PCR (qRT-PCR) revealed that both endogenous (Cell-1) and symbiotic cellulases (Cell-2, 3, and 4) have highest expression in the wood-feeding worker and nymph phenotypes, whereas expression is lowest in presoilder phenotypes and eggs. Worker and nymph phenotypes apparently serve as the “cellulase gene reservoir” for feeding and distribution purposes, and thus is centrally important for the sustenance, maintance, and dispersal of termite colonies. qRT-PCR also showed that the endogenous Cell-1 gene is predominantly expressed in the salivary gland/foregut, whereas symbiotic Cell-2, 3, and 4 are primarily expressed in the hindgut where cellulolytic protists are harbored. In the parallel study, cellulase activity assays were carried out to map distribution patterns of endoglucanase, exoglucanase, b
-glucosidase, and xylanase activity throughout the R. flavipes digestive tract. Cellulase gene expression correlated well with the specific types of cellulolytic activity observed in each gut region. In light of these findings, we suggest the presence of a single cellulose digestion system across the entire digestive tract of R. flavipes, whereby endogenous and symbiotic cellulases work sequentially and collaboratively.
See more of Posters and Exhibits, Group B
See more of Poster Presentations
See more of The IUSSI 2006 Congress