title: Sterol Methyl Oxidases Affect Embryo Development via Auxin-Associated Mechanisms.
abstract: Sterols are essential molecules for multiple biological processes, including embryogenesis, cell elongation, and endocytosis. The plant sterol biosynthetic pathway is unique in the involvement of two distinct sterol 4α-methyl oxidase (SMO) families, SMO1 and SMO2, which contain three and two isoforms, respectively, and are involved in sequential removal of the two methyl groups at C-4. In this study, we characterized the biological functions of members of the SMO2 gene family. SMO2-1 was strongly expressed in most tissues during Arabidopsis (Arabidopsis thaliana) development, whereas SMO2-2 showed a more specific expression pattern. Although single smo2 mutants displayed no obvious phenotype, the smo2-1 smo2-2 double mutant was embryonic lethal, and the smo2-1 smo2-2/+ mutant was dwarf, whereas the smo2-1/+ smo2-2 mutant exhibited a moderate phenotype. The phenotypes of the smo2 mutants resembled those of auxin-defective mutants. Indeed, the expression of DR5rev:GFP, an auxin-responsive reporter, was reduced and abnormal in smo2-1 smo2-2 embryos. Furthermore, the expression and subcellular localization of the PIN1 auxin efflux facilitator also were altered. Consistent with these observations, either the exogenous application of auxin or endogenous auxin overproduction (YUCCA9 overexpression) partially rescued the smo2-1 smo2-2 embryonic lethality. Surprisingly, the dwarf phenotype of smo2-1 smo2-2/+ was completely rescued by YUCCA9 overexpression. Gas chromatography-mass spectrometry analysis revealed a substantial accumulation of 4α-methylsterols, substrates of SMO2, in smo2 heterozygous double mutants. Together, our data suggest that SMO2s are important for correct sterol composition and function partially through effects on auxin accumulation, auxin response, and PIN1 expression to regulate Arabidopsis embryogenesis and postembryonic development.
authors.affiliation: Department of Plant Biology and Ecology, College of Life Sciences, Nankai University, 300071 Tianjin, China (X.Z., S.S., X.N., P.L., S.K., S.M.); andCentre National de la Recherche Scientifique-University of Bordeaux, Unité Mixte de Recherche 5200 Membrane Biogenesis Laboratory, Institut National de la Recherche Agronomique Bordeaux Aquitaine, 33140 Villenave d'Ornon, France (Y.B., M.G.).
authors.forename: Xia
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Plant Biology and Ecology, College of Life Sciences, Nankai University, 300071 Tianjin, China (X.Z., S.S., X.N., P.L., S.K., S.M.); andCentre National de la Recherche Scientifique-University of Bordeaux, Unité Mixte de Recherche 5200 Membrane Biogenesis Laboratory, Institut National de la Recherche Agronomique Bordeaux Aquitaine, 33140 Villenave d'Ornon, France (Y.B., M.G.).
authors.forename: Shuangli
authors.initials: S
authors.lastname: Sun
authors.affiliation: Department of Plant Biology and Ecology, College of Life Sciences, Nankai University, 300071 Tianjin, China (X.Z., S.S., X.N., P.L., S.K., S.M.); andCentre National de la Recherche Scientifique-University of Bordeaux, Unité Mixte de Recherche 5200 Membrane Biogenesis Laboratory, Institut National de la Recherche Agronomique Bordeaux Aquitaine, 33140 Villenave d'Ornon, France (Y.B., M.G.).
authors.forename: Xiang
authors.initials: X
authors.lastname: Nie
authors.affiliation: Department of Plant Biology and Ecology, College of Life Sciences, Nankai University, 300071 Tianjin, China (X.Z., S.S., X.N., P.L., S.K., S.M.); andCentre National de la Recherche Scientifique-University of Bordeaux, Unité Mixte de Recherche 5200 Membrane Biogenesis Laboratory, Institut National de la Recherche Agronomique Bordeaux Aquitaine, 33140 Villenave d'Ornon, France (Y.B., M.G.).
authors.forename: Yohann
authors.initials: Y
authors.lastname: Boutté
authors.affiliation: Department of Plant Biology and Ecology, College of Life Sciences, Nankai University, 300071 Tianjin, China (X.Z., S.S., X.N., P.L., S.K., S.M.); andCentre National de la Recherche Scientifique-University of Bordeaux, Unité Mixte de Recherche 5200 Membrane Biogenesis Laboratory, Institut National de la Recherche Agronomique Bordeaux Aquitaine, 33140 Villenave d'Ornon, France (Y.B., M.G.).
authors.forename: Magali
authors.initials: M
authors.lastname: Grison
authors.affiliation: Department of Plant Biology and Ecology, College of Life Sciences, Nankai University, 300071 Tianjin, China (X.Z., S.S., X.N., P.L., S.K., S.M.); andCentre National de la Recherche Scientifique-University of Bordeaux, Unité Mixte de Recherche 5200 Membrane Biogenesis Laboratory, Institut National de la Recherche Agronomique Bordeaux Aquitaine, 33140 Villenave d'Ornon, France (Y.B., M.G.).
authors.forename: Panpan
authors.initials: P
authors.lastname: Li
authors.affiliation: Department of Plant Biology and Ecology, College of Life Sciences, Nankai University, 300071 Tianjin, China (X.Z., S.S., X.N., P.L., S.K., S.M.); andCentre National de la Recherche Scientifique-University of Bordeaux, Unité Mixte de Recherche 5200 Membrane Biogenesis Laboratory, Institut National de la Recherche Agronomique Bordeaux Aquitaine, 33140 Villenave d'Ornon, France (Y.B., M.G.).
authors.forename: Susu
authors.initials: S
authors.lastname: Kuang
authors.affiliation: Department of Plant Biology and Ecology, College of Life Sciences, Nankai University, 300071 Tianjin, China (X.Z., S.S., X.N., P.L., S.K., S.M.); andCentre National de la Recherche Scientifique-University of Bordeaux, Unité Mixte de Recherche 5200 Membrane Biogenesis Laboratory, Institut National de la Recherche Agronomique Bordeaux Aquitaine, 33140 Villenave d'Ornon, France (Y.B., M.G.) shuzhenmen@nankai.edu.cn.
authors.forename: Shuzhen
authors.identifier: 0000-0001-6472-6829
authors.initials: S
authors.lastname: Men
mesh_terms: D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D056625:Endosperm / Q000235:genetics / Q000254:growth & development; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010840:Phytosterols / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D030821:Plants, Genetically Modified; D012639:Seeds / Q000254:growth & development* / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins; C116363:PIN1 protein, Arabidopsis; D010840:Phytosterols; D006899:Mixed Function Oxygenases; C027532:methylsterol monooxygenase