Abstract
BackgroundThe development of fast-growing hardwood trees as a source of lignocellulosic biomass for biofuel and biomaterial production requires a thorough understanding of the plant cell wall structure and function that underlie the inherent recalcitrance properties of woody biomass. Downregulation of GAUT12.1 in Populus deltoides was recently reported to result in improved biomass saccharification, plant growth, and biomass yield. To further understand GAUT12.1 function in biomass recalcitrance and plant growth, here we report the effects of P. trichocarpa GAUT12.1 overexpression in P. deltoides.ResultsIncreasing GAUT12.1 transcript expression by 7–49% in P. deltoides PtGAUT12.1-overexpression (OE) lines resulted in a nearly complete opposite biomass saccharification and plant growth phenotype to that observed previously in PdGAUT12.1-knockdown (KD) lines. This included significantly reduced glucose, xylose, and total sugar release (12–13%), plant height (6–54%), stem diameter (8–40%), and overall total aerial biomass yield (48–61%) in 3-month-old, greenhouse-grown PtGAUT12.1-OE lines compared to controls. Total lignin content was unaffected by the gene overexpression. Importantly, selected PtGAUT12.1-OE lines retained the recalcitrance and growth phenotypes upon growth for 9 months in the greenhouse and 2.8 years in the field. PtGAUT12.1-OE plants had significantly smaller leaves with lower relative water content, and significantly reduced stem wood xylem cell numbers and size. At the cell wall level, xylose and galacturonic acid contents increased markedly in total cell walls as well as in soluble and insoluble cell wall extracts, consistent with increased amounts of xylan and homogalacturonan in the PtGAUT12.1-OE lines. This led to increased cell wall recalcitrance, as manifested by the 9–15% reduced amounts of recovered extractable wall materials and 8–15% greater amounts of final insoluble pellet in the PtGAUT12.1-OE lines compared to controls.ConclusionsThe combined phenotype and chemotype data from P. deltoides PtGAUT12.1-OE and PdGAUT12.1-KD transgenics clearly establish GAUT12.1 as a recalcitrance- and growth-associated gene in poplar. Overall, the data support the hypothesis that GAUT12.1 synthesizes either an HG-containing primer for xylan synthesis or an HG glycan required for proper xylan deposition, anchoring, and/or architecture in the wall, and the possibility of HG and xylan glycans being connected to each other by a base-sensitive covalent linkage.
Highlights
The development of fast-growing hardwood trees as a source of lignocellulosic biomass for biofuel and biomaterial production requires a thorough understanding of the plant cell wall structure and function that underlie the inherent recalcitrance properties of woody biomass
The data support the hypothesis that GAUT12.1 synthesizes either an HG-containing primer for xylan synthesis or an HG glycan required for proper xylan deposition, anchoring, and/or architecture in the wall, and the possibility of HG and xylan glycans being connected to each other by a base-sensitive covalent linkage
Populus GAUT12.1 is expressed in the shoot apex, young developing leaves, and internodes, as well as in secondary wall‐rich stem and root tissues, indicating a broader role for GAUT12 than only in secondary walls Previous studies of GAUT12 primarily emphasized its function in secondary cell walls, focusing mostly on stem tissues [13,14,15,16] and woody biomass [5, 22, 23]
Summary
The development of fast-growing hardwood trees as a source of lignocellulosic biomass for biofuel and biomaterial production requires a thorough understanding of the plant cell wall structure and function that underlie the inherent recalcitrance properties of woody biomass. Understanding the structural complexity, interaction, and functionality of the cell wall polymers is essential for unraveling the molecular basis of biomass recalcitrance and plant growth, and to generate by biotechnological manipulation improved biomass with reduced recalcitrance and high yield. We identified a recalcitrance-associated gene, GAlactUronosylTransferase (GAUT) whose modified expression in poplar led to both reduced biomass recalcitrance and increased plant growth [5]. GAUT12 was first identified as a gene involved in Arabidopsis thaliana (At) secondary wall formation [11, 12]. Compared to wild type (WT), Arabidopsis irx mutant cell walls have a greater than 50% reduction in glucuronoxylan (GX) and an almost complete absence of the β-d-Xylp-(1,3)-α-l-Rhap-(1,2)α-d-GalpA-(1,4)-d-Xylp xylan reducing end tetrasaccharide sequence, indicating a critical role of AtGAUT12 in
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
