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PMID:22537759

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Citation

Lee, C, Teng, Q, Zhong, R and Ye, ZH (2012) Arabidopsis GUX proteins are glucuronyltransferases responsible for the addition of glucuronic acid side chains onto xylan. Plant Cell Physiol. 53:1204-16

Abstract

Xylan, the second most abundant cell wall polysaccharide, is composed of a linear backbone of β-(1,4)-linked xylosyl residues that are often substituted with sugar side chains, such as glucuronic acid (GlcA) and methylglucuronic acid (MeGlcA). It has recently been shown that mutations of two Arabidopsis family GT8 genes, GUX1 and GUX2, affect the addition of GlcA and MeGlcA to xylan, but it is not known whether they encode glucuronyltransferases (GlcATs) or indirectly regulate the GlcAT activity. In this study, we performed biochemical and genetic analyses of three Arabidopsis GUX genes to determine their roles in the GlcA substitution of xylan and secondary wall deposition. The GUX1/2/3 genes were found to be expressed in interfascicular fibers and xylem cells, the two major types of secondary wall-containing cells that have abundant xylan. When expressed in tobacco BY2 cells, the GUX1/2/3 proteins exhibited an activity capable of transferring GlcA residues from the UDP-GlcA donor onto xylooligomer acceptors, demonstrating that these GUX proteins possess xylan GlcAT activity. Analyses of the single, double and triple gux mutants revealed that simultaneous mutations of all three GUX genes led to a complete loss of GlcA and MeGlcA side chains on xylan, indicating that all three GUX proteins are involved in the GlcA substitution of xylan. Furthermore, a complete loss of GlcA and MeGlcA side chains in the gux1/2/3 triple mutant resulted in reduced secondary wall thickening, collapsed vessel morphology and reduced plant growth. Together, our results provide biochemical and genetic evidence that GUX1/2/3 are GlcATs responsible for the GlcA substitution of xylan, which is essential for normal secondary wall deposition and plant development.

Links

PubMed Online version:10.1093/pcp/pcs064

Keywords


Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

ARATH:GUX2

acts_upstream_of_or_within

GO:0009834: plant-type secondary cell wall biogenesis

ECO:0000316: genetic interaction evidence used in manual assertion

AGI_LocusCode:At1g77130
AGI_LocusCode:At3g18660

P

Seeded From UniProt

complete

ARATH:GUX2

enables

GO:0015020: glucuronosyltransferase activity

ECO:0000314: direct assay evidence used in manual assertion

F

Seeded From UniProt

complete

ARATH:GUX2

acts_upstream_of_or_within

GO:0045492: xylan biosynthetic process

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete

ARATH:GUX2

acts_upstream_of_or_within

GO:0045492: xylan biosynthetic process

ECO:0000316: genetic interaction evidence used in manual assertion

AGI_LocusCode:At1g77130
AGI_LocusCode:At3g18660

P

Seeded From UniProt

complete

ARATH:GUX3

acts_upstream_of_or_within

GO:0009834: plant-type secondary cell wall biogenesis

ECO:0000316: genetic interaction evidence used in manual assertion

AGI_LocusCode:AT3G18660
AGI_LocusCode:At4g33330

P

Seeded From UniProt

complete

ARATH:GUX3

enables

GO:0015020: glucuronosyltransferase activity

ECO:0000314: direct assay evidence used in manual assertion

F

Seeded From UniProt

complete

ARATH:GUX3

acts_upstream_of_or_within

GO:0045492: xylan biosynthetic process

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete

ARATH:GUX3

acts_upstream_of_or_within

GO:0045492: xylan biosynthetic process

ECO:0000316: genetic interaction evidence used in manual assertion

AGI_LocusCode:AT3G18660
AGI_LocusCode:At4g33330

P

Seeded From UniProt

complete

ARATH:GUX1

acts_upstream_of_or_within

GO:0009834: plant-type secondary cell wall biogenesis

ECO:0000316: genetic interaction evidence used in manual assertion

AGI_LocusCode:At1g77130
AGI_LocusCode:At4g33330

P

Seeded From UniProt

complete

ARATH:GUX1

enables

GO:0015020: glucuronosyltransferase activity

ECO:0000314: direct assay evidence used in manual assertion

F

Seeded From UniProt

complete

ARATH:GUX1

acts_upstream_of_or_within

GO:0045492: xylan biosynthetic process

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete

ARATH:GUX1

acts_upstream_of_or_within

GO:0045492: xylan biosynthetic process

ECO:0000316: genetic interaction evidence used in manual assertion

AGI_LocusCode:At1g77130
AGI_LocusCode:At4g33330

P

Seeded From UniProt

complete


See also

References

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