title: Male gametophyte defective 4 encodes a rhamnogalacturonan II xylosyltransferase and is important for growth of pollen tubes and roots in Arabidopsis.
abstract: In flowering plants, the growth of pollen tubes is essential for the delivery of sperm to the egg cells. Although many factors (including cell-wall properties) are involved in this process, little is known about the underlying molecular mechanisms that regulate the growth of pollen tubes. We report here the characterization of an Arabidopsis mutant male gametophyte defective 4 (mgp4) that is severely defective in pollen tube growth. The mgp4 mutation also impairs root growth of pollen-rescued mgp4 mutant plants generated by expressing MGP4 cDNA under the control of a pollen grain/tube-specific promoter. The MGP4 gene encodes a putative xylosyltransferase and is expressed in many organs/tissues, including pollen tubes and roots. MGP4 protein expressed in Pichia pastoris exhibited xylosyltransferase activity and transferred d-xylose onto l-fucose. The pectic polysaccharide rhamnogalacturonan II (RG-II), isolated from 7-day-old pollen-rescued mutant seedlings, exhibited a 30% reduction in 2-O-methyl d-xylose residues. Furthermore, an exogenous supply of boric acid enhanced RG-II dimer formation and partially restored the root growth of the pollen-rescued mutant seedlings. Taken together, these results suggest that MGP4 plays important roles in pollen tube and root growth by acting as a xylosyltransferase involved in the biosynthesis of pectic RG-II.
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
authors.forename: Xiao-Lei
authors.initials: XL
authors.lastname: Liu
authors.forename: Lifeng
authors.initials: L
authors.lastname: Liu
authors.forename: Qian-Kun
authors.initials: QK
authors.lastname: Niu
authors.forename: Chuan
authors.initials: C
authors.lastname: Xia
authors.forename: Ke-Zhen
authors.initials: KZ
authors.lastname: Yang
authors.forename: Rui
authors.initials: R
authors.lastname: Li
authors.forename: Li-Qun
authors.initials: LQ
authors.lastname: Chen
authors.forename: Xue-Qin
authors.initials: XQ
authors.lastname: Zhang
authors.forename: Yihua
authors.initials: Y
authors.lastname: Zhou
authors.forename: De
authors.initials: D
authors.lastname: Ye
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D018744:DNA, Plant / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D006056:Golgi Apparatus / Q000201:enzymology; D009154:Mutation; D010368:Pectins / Q000096:biosynthesis*; D010430:Pentosyltransferases / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000254:growth & development*; D053205:Pollen Tube / Q000201:enzymology / Q000254:growth & development*; D011401:Promoter Regions, Genetic; D000097608:UDP Xylose-Protein Xylosyltransferase
chemical_list: D029681:Arabidopsis Proteins; D018744:DNA, Plant; D010368:Pectins; D010430:Pentosyltransferases; D000097608:UDP Xylose-Protein Xylosyltransferase; C042492:rhamnogalacturonan II