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

Journal Article · · BMC Plant Biology
 [1];  [2];  [1];  [2];  [2];  [2];  [3]
  1. Joint BioEnergy Institute, Emeryville, CA (United States). Feedstocks Div.; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of Copenhagen, Frederiksberg (Denmark)
  2. Joint BioEnergy Institute, Emeryville, CA (United States). Feedstocks Div.; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  3. Joint BioEnergy Institute, Emeryville, CA (United States). Feedstocks Div.; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)
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Background: Engineering 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. Results: First 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. Conclusions: This 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.

Research Organization:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Biological and Environmental Research (BER)
Grant/Contract Number:
AC02-05CH11231
OSTI ID:
1213421
Journal Information:
BMC Plant Biology, Vol. 14, Issue 1; ISSN 1471-2229
Publisher:
BioMed CentralCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 24 works
Citation information provided by
Web of Science

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Cited By (12)

The Three Members of the Arabidopsis Glycosyltransferase Family 92 are Functional β-1,4-Galactan Synthases journal September 2018
Bifunctional glycosyltransferases catalyze both extension and termination of pectic galactan oligosaccharides journal March 2018
Plant synthetic biology could drive a revolution in biofuels and medicine journal September 2018
Mapping regulatory variants controlling gene expression in drought response and tolerance in maize journal July 2020
Gene stacking of multiple traits for high yield of fermentable sugars in plant biomass journal January 2018
A transgene design for enhancing oil content in Arabidopsis and Camelina seeds journal February 2018
Increased drought tolerance in plants engineered for low lignin and low xylan content journal July 2018
Stacking of a low-lignin trait with an increased guaiacyl and 5-hydroxyguaiacyl unit trait leads to additive and synergistic effects on saccharification efficiency in Arabidopsis thaliana journal September 2018
Designer biomass for next-generation biorefineries: leveraging recent insights into xylan structure and biosynthesis journal November 2017
A Transcriptomic Analysis of Xylan Mutants Does Not Support the Existence of a Secondary Cell Wall Integrity System in Arabidopsis. journalarticle January 2018
Xylan in the Middle: Understanding Xylan Biosynthesis and Its Metabolic Dependencies Toward Improving Wood Fiber for Industrial Processing journal February 2019
Engineering of Bioenergy Crops: Dominant Genetic Approaches to Improve Polysaccharide Properties and Composition in Biomass journal March 2020

Figures / Tables (9)

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Table 1(p. 9)table Table 1
Table 2(p. 9)table Table 2

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Related Subjects

09 BIOMASS FUELS
60 APPLIED LIFE SCIENCES
plant cell wall
UDP-glucose 4-epimerase
Galactan
Pectin
Arabidopsis
Populus
gene stacking
GalS1
NST1
artificial positive feedback loop