Skip to main content

Table 1 Targeted genetic engineering of plant cell wall chemical constituents for improved industrial utility

From: Tailoring renewable materials via plant biotechnology

Cell wall compound

Gene

Type of modification

Outcomes

Plant

References

Pectin

PL1-27

OE

Increased xylose (21%) and glucose (7%) yields

Poplar

[55]

RG-lyase6

OE

Increased xylose (4%) and glucose (25%) yields

Poplar

[51]

PMEI2

OE

Reduced proportion of egg box structures

Increased saccharification (40%) yields

Arabidopsis

[58]

GAUT4

RNAi

Reduced HG and RG-I content, calcium, borate, and ferulate cross-linking

Increased lignin migration and hemicellulose dissolution

Switchgrass and Poplar

[60,61]

GAUT12

RNAi

Increased glucose release, plant height, and stem radius

Poplar

[62]

Xyloglucan

XEG2 (Aspergillus aculeatus)

OE

Increased stem height and cellulose content

Affected development of G-layers

Increased glucose (50%) yields

Increased cellulose conversion (60%)

Poplar

[79, 81, 82, 95]

XTH4 and XTH9

KO (T-DNA insertion)

Reduced XET activity

Altered xylem cell expansion and production, and secondary cell deposition

Increased carbohydrate production (15%)

Arabidopsis

[84]

XET16-34

OE

Stimulated cell expansion in vessel elements

Increased overall xyloglucan content

Poplar

[83]

BGAL10

KO (T-DNA insertion)

Reduced β-galactosidase activity against XyG

Altered XyG composition and plant growth

Arabidopsis

[104]

Xylan

ESK1

KO (T-DNA insertion and induced point mutation)

Dwarf plants

Collapsed xylem vessels

Arabidopsis

[106]

DARX1

KO (CRISPR/Cas9 mutation)

Altered arabinoxylan conformation and cellulose microfibril orientation

Reduced mechanical stem strength and plant height

Rice

[117]

GUX1 and GUX2

KO (T-DNA insertion)

Weak stems

Increased glucose (30%) release

Increased xylose (700%) release

Increased ethanol yields

Arabidopsis

[118, 119]

ARAF1 and ARAF2

OE

Reduced arabinose (up to 25%) content

Increased glucose (up to 34%) release

Rice

[126]

AT10 from Rice

OE

Reduced ferulic acid levels

Increased saccharification efficiency (40%)

Switchgrass

[127]

Mannan

CSLA2,3,7, and 9

KO (T-DNA insertion)

CSLA 7 is essential for embryogenesis

CSLA 2,3,9 reduced glucomannan content without affecting plant growth

Arabidopsis

[144]

MUCI10

KO (T-DNA insertion)

Altered seed mucilage density and cellulose structure

Arabidopsis

[150]

Cellulose

CesA1 and 9

KO (T-DNA insertion and point mutation)

Reduced cellulose crystallinity (up to 34%)

Increased fermentable sugar release (up to 151%)

Reduced anisotropic growth

Arabidopsis

[168, 171, 172]

CesA4, CesA7-A/B, and CesA8-A/B

RNAi

Reduced cellulose content and plant growth

Collapsed vessels and thinner fibre cell walls

Stems exhibited reduced mechanical strength

Poplar

[173]

RIC1

OE

Reduced cellulose crystallinity

Arabidopsis

[174]

Cel9A6 and KOR1

RNAi

Collapsed xylem vessels

Reduced cellulose content and crystallinity

Reduced stem mechanical strength

Poplar

[176, 177]

Cel9A6

OE

Increased plant growth and fibre cell length

Caused male sterility

Arabidopsis

[176]

Cel9A1/KOR1

OE

Reduced cellulose crystallinity

Improved glucose yields

Arabidopsis

[179]

GH9B1 and GH9B3

OE

Reduced cellulose degree polymerization and crystallinity

Increased bioethanol yields

Rice

[180]

SuSy

OE

Increased cellulose content (up to 6%) and crystallinity

Increased wood density

Poplar

[185]

SUS3

OE

Reduced cellulose crystallinity and xylose–arabinose proportions

Increased stress-induced callose accumulation

Rice

[186]

Lignin

4CL

RNAi

Reduced lignin, changed lignin composition, growth impairments

Poplar

[215]

HCT

RNAi

Reduced lignin, changed lignin composition, growth impairments

Poplar, alfalfa

[216, 218, 219]

CCR

RNAi

Reduced lignin, changed lignin composition (incorporation of ferulic acid, increase in acetal bonds), growth impairments

Poplar, maize

[217, 260]

C4H

RNAi

Reduced lignin, changed lignin composition, growth impairments

Alfalfa

[218, 219]

C3′H

RNAi

Reduced lignin, changed lignin composition, growth impairments

Alfalfa

[218, 219]

PAL

RNAi

Reduced lignin content, but no growth impairments

Poplar

[216]

Ref8-1 med5a/med5b

KO (Triple mutant T-DNA insertion)

Restoration of growth of the ref8-1 (c3h), lignin almost completely composed of H units

Arabidopsis

[226]

HCHL

OE

Reduced lignin degree of polymerization, but no differences in biomass yield or lignin amount. Increased saccharification efficiency

Arabidopsis

[229]

CHS

Natural mutant (C2-Idf)

Reduced incorporation of tricin in the lignin, lignin was enriched in β–β and β-5 units

Maize

[232]

Sfe

Transposon Mutant

Reduced feruloylation, better forage digestibility

Maize

[237,238,241]

Gt61

Natural KO mutant (xax1)

Reduced arabinosyl substitutions, increased processing efficiency, dwarfed

Rice

[124]

COMT

KO and RNAi

Incorporation of 5-hydroxyconiferyl alcohol, increase in benzodioxane structures in the lignin, but no lignin reductions. Increased saccharification efficiency

Arabidopsis, Poplar

[243, 244]

F5H

OE

Increased S units (around 90% of all lignin monomers), increased monomer yield after hydrogenolysis

Poplar

[40, 258]

FMT

OE

Incorporation of ester linkages in the lignin backbone, increased saccharification efficiency after alkaline pretreatment, increased pulping efficiency

Poplar

[216, 260]

PMT

OE

Incorporation of p-coumarate conjugates in the lignin, higher frequency of terminal units with free phenolic groups

Arabidopsis, Poplar

[263, 264]

DCS & CURS2

OE

Incorporation of curcumin in the lignin, increased saccharifcation efficiency

Arabidopsis

[265]

Cα-dehydrogenase

OE

Appearance of chemical labile α-keto-β-ether units in the lignin

Arabidopsis

[266]

CAD

RNAi and KO mutants

Increased concentrations of aldehydeS, increased saccharification efficiency

Pine, Arabidopsis, Medicago, Poplar

[230, 243]

QsuB

OE

Reduced lignin concentrations

Arabidopsis

[282]

  1. OE overexpression, RNAi RNA interference, KO gene knockout, T-DNA transfer DNA