A gene stacking approach leads to engineered plants with highly increased galactan levels in Arabidopsis

BMC Plant Biology

Research Article

April JM Liwanag¹  Rhea Stoppel¹  Carsten Rautengarten¹  Dominique Loqué¹  Berit Ebert²  Vibe M Gondolf²  Henrik V Scheller³ 

[1] Feedstocks Division, Joint BioEnergy Institute, 94608, Emeryville, California, USA;Physical Biosciences Division, Lawrence Berkeley National Laboratory, 94720, Berkeley, California, USA;Feedstocks Division, Joint BioEnergy Institute, 94608, Emeryville, California, USA;Physical Biosciences Division, Lawrence Berkeley National Laboratory, 94720, Berkeley, California, USA;Department of Plant and Environmental Sciences, University of Copenhagen, DK-1871, Frederiksberg C, Denmark;Feedstocks Division, Joint BioEnergy Institute, 94608, Emeryville, California, USA;Physical Biosciences Division, Lawrence Berkeley National Laboratory, 94720, Berkeley, California, USA;Department of Plant and Microbial Biology, University of California, 94720, Berkeley, California, USA;

关键词: Plant cell wall;    UDP-glucose 4-epimerase;    Galactan;    Pectin;    Arabidopsis;    Populus;    Gene stacking;    GalS1;    NST1;    Artificial positive feedback loop;   

DOI  :  10.1186/s12870-014-0344-x

 received in 2014-09-10, accepted in 2014-11-20,  发布年份 2014

来源: Springer

【 摘 要 】

BackgroundEngineering of plants with a composition of lignocellulosic biomass that is more suitable for downstream processing is of high interest for next-generation biofuel production. Lignocellulosic biomass contains a high proportion of pentose residues, which are more difficult to convert into fuels than hexoses. Therefore, increasing the hexose/pentose ratio in biomass is one approach for biomass improvement. A genetic engineering approach was used to investigate whether the amount of pectic galactan can be specifically increased in cell walls of Arabidopsis fiber cells, which in turn could provide a potential source of readily fermentable galactose.ResultsFirst it was tested if overexpression of various plant UDP-glucose 4-epimerases (UGEs) could increase the availability of UDP-galactose and thereby increase the biosynthesis of galactan. Constitutive and tissue-specific expression of a poplar UGE and three Arabidopsis UGEs in Arabidopsis plants could not significantly increase the amount of cell wall bound galactose. We then investigated co-overexpression of AtUGE2 together with the β-1,4-galactan synthase GalS1. Co-overexpression of AtUGE2 and GalS1 led to over 80% increase in cell wall galactose levels in Arabidopsis stems, providing evidence that these proteins work synergistically. Furthermore, AtUGE2 and GalS1 overexpression in combination with overexpression of the NST1 master regulator for secondary cell wall biosynthesis resulted in increased thickness of fiber cell walls in addition to the high cell wall galactose levels. Immunofluorescence microscopy confirmed that the increased galactose was present as β-1,4-galactan in secondary cell walls.ConclusionsThis approach clearly indicates that simultaneous overexpression of AtUGE2 and GalS1 increases the cell wall galactose to much higher levels than can be achieved by overexpressing either one of these proteins alone. Moreover, the increased galactan content in fiber cells while improving the biomass composition had no impact on plant growth and development and hence on the overall biomass amount. Thus, we could show that the gene stacking approach described here is a promising method to engineer advanced feedstocks for biofuel production.

【 授权许可】

Unknown   
© Gondolf et al.; licensee BioMed Central Ltd. 2014. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.