In silico comparative analysis of glycoside hydrolase (GH) family 10 endo-(1-4)-beta-xylanase genes from Eucalyptus grandis and Arabidopsis thaliana
© Mewalal et al; licensee BioMed Central Ltd. 2011
Published: 13 September 2011
The hemicellulose xylan constitutes the major non-cellulosic component of plant secondary cell walls. It has been shown that xylan adsorbs to cellulose fibres and also covalently binds a carbon moiety of lignin [1, 2]. Eucalyptus is an important hardwood tree genus used in the pulp and paper industry and has potential as biofuel feedstock. Xylan removal is expensive and uses environmentally harsh chemical treatments . Previous studies have shown that endo-(1-4)-β-xylanase enzymes belonging to glycoside hydrolase (GH) family 10 internally attacks the xylan backbone resulting in shorter xylo-saccharide chains . The recently sequenced Eucalyptus grandis genome (DOE-JGI, http://www.phytozome.net) provides a unique opportunity to analyze the native endo-(1-4)-beta-xylanase proteins involved in xylan modification in eucalypt fibre cell walls. Detailed knowledge of endogenous xylanolytic enzymes from Eucalyptus could facilitate the development of strategies to enhance the processing of woody biomass for cellulose and biofuel production. The aims of this study are to identify xylem secondary cell wall-related endo-(1-4)-β-xylanase genes in the E. grandis genome and to perform a comparative analysis of the Eucalyptus xylanasepeptide sequences with those of previously studied Arabidopsis orthologs to provide a framework for assigning function to the Eucalyptus enzymes.
The E. grandis genome contains 18 putative GH10 family members (at a BLAST threshold of 1e-10). One of these, EgrXYN1 is highly preferentially expressed in Eucalyptus xylem tissues and shows highest similarity to AtXYN1. The similarities between AtXYN1and EgrXYN1 suggest similar biochemical properties and biological functions. Previous studies showed that AtXYN1::eGFP localized to the cell wall providing support for its function in cell wall modification. AtXYN1prom::GUS constructs expressed predominately in the vascular bundles suggesting that AtXYN1 (and therefore putatively EgrXYN1) is involved in secondary cell wall modification [4, 7]. Future work will involve experimental validation of the biochemical properties and enzyme kinetics of EgrXYN1.
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