Expressions of thermostable bacterial cellulases in tobacco plant
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An economical method for the conversion of lignocellulosic biomass is to use plants as bioreactors for cellulases production. Two bacterial thermostable cellulases (E2 and E3) and a E3-E2 fusion form were expressed in tobacco, driven by a double 35S promoter and 5′ TEV-UTL. The enzymes were targeted to the apoplast and cytosol via 5′ signal peptides and 3′ retention signal peptides, respectively, and all showed functional activities. All transgenic plants exhibited normal growth compared to wild type. Transgenic plants that expressed apoplast-localized E2 had the highest average activity, about 1.5 and 3 times higher than those expressed ER-localized and cytosolic E2, respectively. Effect of subcellular compartment localization was due primarily to post-transcriptional modification, since mRNA abundances were similar despite the range of cellulase activities obtained. The recombinant cellulases exhibited good thermostability below 65°C. After storing for 3 days at −20 and 28°C, the enzymes lost nearly 20 and 80% of activity, respectively. The results suggested a potential application for heterologous expression of cellulases in plant for biomass conversion.
KeywordsBiomass Cellulase Sub-cellular targeting Transgenic tobacco
Cauliflower Mosaic Virus 35s
Tobacco etch virus
Tobacco calreticulin signal peptide
The work was supported by “the Fundamental Research Funds for the Central Universities” (DUT10JN01) and China Environmental Protection Foundation Liaoning Representative Office. Liaoning environmental scientific research “123” fund project (CEPF2008-123-2-11). We thank Alan K Chang (Dalian University of Technology) for helpful discussion and for revising the manuscript.
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