Arabidopsis fragile fiber8, which encodes a putative glucuronyltransferase, is essential for normal secondary wall synthesis.
Secondary walls in vessels and fibers of dicotyledonous plants are mainly composed of cellulose, xylan, and lignin. Although genes involved in biosynthesis of cellulose and lignin have been intensively studied, little is known about genes participating in xylan synthesis. We found that Arabidopsis thaliana fragile fiber8 (fra8) is defective in xylan synthesis. The fra8 mutation caused a dramatic reduction in fiber wall thickness and a decrease in stem strength. FRA8 was found to encode a member of glycosyltransferase family 47 and exhibits high sequence similarity to tobacco (Nicotiana plumbaginifolia) pectin glucuronyltransferase. FRA8 is expressed specifically in developing vessels and fiber cells, and FRA8 is targeted to Golgi. Comparative analyses of cell wall polysaccharide fractions from fra8 and wild-type stems showed that the xylan and cellulose contents are drastically reduced in fra8, whereas xyloglucan and pectin are elevated. Further structural analysis of cell walls revealed that although wild-type xylans contain both glucuronic acid and 4-O-methylglucuronic acid residues, xylans from fra8 retain only 4-O-methylglucuronic acid, indicating that the fra8 mutation results in a specific defect in the addition of glucuronic acid residues onto xylans. These findings suggest that FRA8 is a glucuronyltransferase involved in the biosynthesis of glucuronoxylan during secondary wall formation.
Zhong
Ruiqin
R
Department of Plant Biology, University of Georgia, Athens, 30602, USA.
Peña
Maria J
MJ
Zhou
Gong-Ke
GK
Nairn
C Joseph
CJ
Wood-Jones
Alicia
A
Richardson
Elizabeth A
EA
Morrison
W Herbert
WH
Darvill
Alan G
AG
York
William S
WS
Ye
Zheng-Hua
ZH
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D002473:Cell Wall / Q000378:metabolism*; D003001:Cloning, Molecular; D018744:DNA, Plant; D017343:Genes, Plant; D014453:Glucuronosyltransferase / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D019906:Nuclear Magnetic Resonance, Biomolecular; D017386:Sequence Homology, Amino Acid; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013347:Subcellular Fractions / Q000201:enzymology
D029681:Arabidopsis Proteins; D018744:DNA, Plant; C515612:FRA8 protein, Arabidopsis; D014453:Glucuronosyltransferase