Molecular insight into lignocellulose digestion by a marine isopod in the absence of gut microbes

TY - JOUR

T1 - Molecular insight into lignocellulose digestion by a marine isopod in the absence of gut microbes

AU - King, Andrew J.

AU - Cragg, Simon M.

AU - Li, Yi

AU - Dymond, Jo

AU - Guille, Matthew J.

AU - Bowles, Dianna J.

AU - Bruce, Neil C.

AU - Graham, Ian A.

AU - McQueen-Mason, Simon J.

PY - 2010/3/23

Y1 - 2010/3/23

N2 - The digestion of lignocellulose is attracting attention both in terms of basic research into its metabolism by microorganisms and animals, and also as a means of converting plant biomass into bio-fuels. Limnoriid wood borers are unusual because, unlike other wood-feeding animals, they do not rely on symbiotic microbes to help digest lignocellulose. The absence of microbes in the digestive tract suggests that limnoriid wood borers produce all the enzymes necessary for lignocellulose digestion themselves. In this study we report that analysis of ESTs from the digestive system of Limnoria quadripunctata reveals a transcriptome dominated by glycosyl hydrolase genes. Indeed, >20% of all ESTs represent genes encoding putative cellulases, including glycosyl hydrolase family 7 (GH7) cellobiohydrolases. These have not previously been reported in animal genomes, but are key digestive enzymes produced by wood-degrading fungi and symbiotic protists in termite guts. We propose that limnoriid GH7 genes are important for the efficient digestion of lignocellulose in the absence of gut microbes. Hemocyanin transcripts were highly abundant in the hepatopancreas transcriptome. Based on recent studies indicating that these proteins may function as phenoloxidases in isopods, we discuss a possible role for hemocyanins in lignin decomposition.

AB - The digestion of lignocellulose is attracting attention both in terms of basic research into its metabolism by microorganisms and animals, and also as a means of converting plant biomass into bio-fuels. Limnoriid wood borers are unusual because, unlike other wood-feeding animals, they do not rely on symbiotic microbes to help digest lignocellulose. The absence of microbes in the digestive tract suggests that limnoriid wood borers produce all the enzymes necessary for lignocellulose digestion themselves. In this study we report that analysis of ESTs from the digestive system of Limnoria quadripunctata reveals a transcriptome dominated by glycosyl hydrolase genes. Indeed, >20% of all ESTs represent genes encoding putative cellulases, including glycosyl hydrolase family 7 (GH7) cellobiohydrolases. These have not previously been reported in animal genomes, but are key digestive enzymes produced by wood-degrading fungi and symbiotic protists in termite guts. We propose that limnoriid GH7 genes are important for the efficient digestion of lignocellulose in the absence of gut microbes. Hemocyanin transcripts were highly abundant in the hepatopancreas transcriptome. Based on recent studies indicating that these proteins may function as phenoloxidases in isopods, we discuss a possible role for hemocyanins in lignin decomposition.

KW - biofuels

KW - cellulase

KW - hemocyanin

KW - phenoloxidase

KW - wood degradation

KW - HORIZONTAL GENE-TRANSFER

KW - WOOD-BORING BIVALVES

KW - CRYSTALLINE CELLULOSE

KW - CLOSTRIDIUM-THERMOCELLUM

KW - PHENOLOXIDASE ACTIVITY

KW - HEMOCYANIN

KW - CRUSTACEA

KW - DEGRADATION

KW - BACTERIAL

KW - SEQUENCE

UR - http://www.scopus.com/inward/record.url?scp=77950388603&partnerID=8YFLogxK

U2 - 10.1073/pnas.0914228107

DO - 10.1073/pnas.0914228107

M3 - Article

SN - 0027-8424

VL - 107

SP - 5345

EP - 5350

JO - Proceedings of the National Academy of Sciences of the United States of America

JF - Proceedings of the National Academy of Sciences of the United States of America

IS - 12

ER -