KNS4/UPEX1: A Type II Arabinogalactan β-(1,3)-Galactosyltransferase Required for Pollen Exine Development.
Pollen exine is essential for protection from the environment of the male gametes of seed-producing plants, but its assembly and composition remain poorly understood. We previously characterized Arabidopsis (Arabidopsis thaliana) mutants with abnormal pollen exine structure and morphology that we named kaonashi (kns). Here we describe the identification of the causal gene of kns4 that was found to be a member of the CAZy glycosyltransferase 31 gene family, identical to UNEVEN PATTERN OF EXINE1, and the biochemical characterization of the encoded protein. The characteristic exine phenotype in the kns4 mutant is related to an abnormality of the primexine matrix laid on the surface of developing microspores. Using light microscopy with a combination of type II arabinogalactan (AG) antibodies and staining with the arabinogalactan-protein (AGP)-specific β-Glc Yariv reagent, we show that the levels of AGPs in the kns4 microspore primexine are considerably diminished, and their location differs from that of wild type, as does the distribution of pectin labeling. Furthermore, kns4 mutants exhibit reduced fertility as indicated by shorter fruit lengths and lower seed set compared to the wild type, confirming that KNS4 is critical for pollen viability and development. KNS4 was heterologously expressed in Nicotiana benthamiana, and was shown to possess β-(1,3)-galactosyltransferase activity responsible for the synthesis of AG glycans that are present on both AGPs and/or the pectic polysaccharide rhamnogalacturonan I. These data demonstrate that defects in AGP/pectic glycans, caused by disruption of KNS4 function, impact pollen development and viability in Arabidopsis.
Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan (T.S., M.Y., S.T., S.I.); and.|ARC Centre of Excellence in Plant Cell Walls, School of BioSciences, University of Melbourne, Victoria 3010, Australia (J.O.N., W.Z., A.v.d.M., E.R.L., M.S.D., A.B.).
Toshiya
T
Suzuki
Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan (T.S., M.Y., S.T., S.I.); and.|ARC Centre of Excellence in Plant Cell Walls, School of BioSciences, University of Melbourne, Victoria 3010, Australia (J.O.N., W.Z., A.v.d.M., E.R.L., M.S.D., A.B.).
Joan Oñate
JO
Narciso
Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan (T.S., M.Y., S.T., S.I.); and.|ARC Centre of Excellence in Plant Cell Walls, School of BioSciences, University of Melbourne, Victoria 3010, Australia (J.O.N., W.Z., A.v.d.M., E.R.L., M.S.D., A.B.).
Wei
W
Zeng
Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan (T.S., M.Y., S.T., S.I.); and.|ARC Centre of Excellence in Plant Cell Walls, School of BioSciences, University of Melbourne, Victoria 3010, Australia (J.O.N., W.Z., A.v.d.M., E.R.L., M.S.D., A.B.).
Allison
A
van de Meene
Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan (T.S., M.Y., S.T., S.I.); and.|ARC Centre of Excellence in Plant Cell Walls, School of BioSciences, University of Melbourne, Victoria 3010, Australia (J.O.N., W.Z., A.v.d.M., E.R.L., M.S.D., A.B.).
Masayuki
M
Yasutomi
Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan (T.S., M.Y., S.T., S.I.); and.|ARC Centre of Excellence in Plant Cell Walls, School of BioSciences, University of Melbourne, Victoria 3010, Australia (J.O.N., W.Z., A.v.d.M., E.R.L., M.S.D., A.B.).
Shunsuke
S
Takemura
Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan (T.S., M.Y., S.T., S.I.); and.|ARC Centre of Excellence in Plant Cell Walls, School of BioSciences, University of Melbourne, Victoria 3010, Australia (J.O.N., W.Z., A.v.d.M., E.R.L., M.S.D., A.B.).
Edwin R
0000-0002-3666-7240
ER
Lampugnani
Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan (T.S., M.Y., S.T., S.I.); and.|ARC Centre of Excellence in Plant Cell Walls, School of BioSciences, University of Melbourne, Victoria 3010, Australia (J.O.N., W.Z., A.v.d.M., E.R.L., M.S.D., A.B.).
Monika S
0000-0002-8921-2725
MS
Doblin
Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan (T.S., M.Y., S.T., S.I.); and.|ARC Centre of Excellence in Plant Cell Walls, School of BioSciences, University of Melbourne, Victoria 3010, Australia (J.O.N., W.Z., A.v.d.M., E.R.L., M.S.D., A.B.).
Antony
0000-0001-7483-8605
A
Bacic
Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan (T.S., M.Y., S.T., S.I.); and guronyan@agr.nagoya-u.ac.jp.|ARC Centre of Excellence in Plant Cell Walls, School of BioSciences, University of Melbourne, Victoria 3010, Australia (J.O.N., W.Z., A.v.d.M., E.R.L., M.S.D., A.B.) guronyan@agr.nagoya-u.ac.jp.
Sumie
0000-0002-6160-7434
S
Ishiguro
D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000378:metabolism*; D001704:Biopolymers / Q000378:metabolism; D002338:Carotenoids / Q000378:metabolism; D000939:Epitopes / Q000378:metabolism; D005298:Fertility; D005685:Galactans / Q000378:metabolism*; D005700:Galactosyltransferases / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D010368:Pectins / Q000378:metabolism; D010641:Phenotype; D011058:Pollen / Q000201:enzymology* / Q000648:ultrastructure
D029681:Arabidopsis Proteins; D001704:Biopolymers; D000939:Epitopes; D005685:Galactans; C009800:sporopollenin; D002338:Carotenoids; D010368:Pectins; D005700:Galactosyltransferases; C005653:arabinogalactan