TY - JOUR
T1 - Correlation of cellulase gene expression and cellulolytic activity throughout the gut of the termite Reticulitermes flavipes
AU - Zhou, Xuguo
AU - Smith, Joseph A.
AU - Oi, Faith M.
AU - Koehler, Philip G.
AU - Bennett, Gary W.
AU - Scharf, Michael E.
N1 - X.Z. conducted sequencing and gene expression studies. J.A.S. conducted enzyme activity assays. We thank Drion Boucias and Marsha Wheeler for many helpful discussions and suggestions, and for manuscript review. We also acknowledge the assistance of Dancia Wu-Scharf for initial EST identification and Matthew Tarver for sequence verification of real-time PCR products. Partial funding of this research was provided by Procter and Gamble Inc., and by the University of Florida Institute of Food and Agricultural Sciences.
PY - 2007/6/15
Y1 - 2007/6/15
N2 - Termites have developed cellulose digestion capabilities that allow them to obtain energy and nutrition from nutritionally poor food sources, such as lignocellulosic plant material and residues derived from it (e.g., wood and humus). Lower termites, which are equipped with both endogenous (i.e., of termite origin) and symbiotic cellulases, feed primarily on wood and wood-related materials. This study investigated cellulase gene diversity, structure, and activity in the lower termite, Reticulitermes flavipes (Kollar). We initially used a metagenomics approach to identify four genes encoding one endogenous and three symbiotic cellulases, which we refer to as Cell-1, -2, -3 and -4. These four genes encode proteins that share significant sequence similarity with known endoglucanases, exoglucanases and xylanases. Phylogenetic analyses further supported these inferred relationships by showing that each of the four cellulase proteins clusters tightly with respective termite, protozoan or fungal cellulases. Gene structure studies revealed that Cell-1, -3 and -4 are intron-free, while Cell-2 contains the first intron sequence to be identified from a termite symbiont cellulase. Quantitative real-time PCR (qRT-PCR) revealed that the endogenous Cell-1 gene is expressed exclusively in the salivary gland/foregut, whereas symbiotic Cell-2, -3, and -4 are highly expressed in the hindgut (where cellulolytic protists are harbored). Cellulase activity assays mapped the distribution pattern of endoglucanase, exoglucanase and xylanase activity throughout the R. flavipes digestive tract. Cellulase gene expression correlated well with the specific types of cellulolytic activities observed in each gut region (foregut + salivary gland, midgut and hindgut). These results suggest the presence of a single unified cellulose digestion system, whereby endogenous and symbiotic cellulases work sequentially and collaboratively across the entire digestive tract of R. flavipes.
AB - Termites have developed cellulose digestion capabilities that allow them to obtain energy and nutrition from nutritionally poor food sources, such as lignocellulosic plant material and residues derived from it (e.g., wood and humus). Lower termites, which are equipped with both endogenous (i.e., of termite origin) and symbiotic cellulases, feed primarily on wood and wood-related materials. This study investigated cellulase gene diversity, structure, and activity in the lower termite, Reticulitermes flavipes (Kollar). We initially used a metagenomics approach to identify four genes encoding one endogenous and three symbiotic cellulases, which we refer to as Cell-1, -2, -3 and -4. These four genes encode proteins that share significant sequence similarity with known endoglucanases, exoglucanases and xylanases. Phylogenetic analyses further supported these inferred relationships by showing that each of the four cellulase proteins clusters tightly with respective termite, protozoan or fungal cellulases. Gene structure studies revealed that Cell-1, -3 and -4 are intron-free, while Cell-2 contains the first intron sequence to be identified from a termite symbiont cellulase. Quantitative real-time PCR (qRT-PCR) revealed that the endogenous Cell-1 gene is expressed exclusively in the salivary gland/foregut, whereas symbiotic Cell-2, -3, and -4 are highly expressed in the hindgut (where cellulolytic protists are harbored). Cellulase activity assays mapped the distribution pattern of endoglucanase, exoglucanase and xylanase activity throughout the R. flavipes digestive tract. Cellulase gene expression correlated well with the specific types of cellulolytic activities observed in each gut region (foregut + salivary gland, midgut and hindgut). These results suggest the presence of a single unified cellulose digestion system, whereby endogenous and symbiotic cellulases work sequentially and collaboratively across the entire digestive tract of R. flavipes.
KW - Endoglucanase
KW - Exoglucanase
KW - Lignocellulose
KW - Symbiont
KW - Xylan
KW - Xylanase
UR - http://www.scopus.com/inward/record.url?scp=34247596341&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=34247596341&partnerID=8YFLogxK
U2 - 10.1016/j.gene.2007.01.004
DO - 10.1016/j.gene.2007.01.004
M3 - Article
C2 - 17408885
AN - SCOPUS:34247596341
SN - 0378-1119
VL - 395
SP - 29
EP - 39
JO - Gene
JF - Gene
IS - 1-2
ER -