title: A critical role of sterols in embryonic patterning and meristem programming revealed by the fackel mutants of Arabidopsis thaliana.
abstract: Here we report a novel Arabidopsis dwarf mutant, fackel-J79, whose adult morphology resembles that of brassinosteroid-deficient mutants but also displays distorted embryos, supernumerary cotyledons, multiple shoot meristems, and stunted roots. We cloned the FACKEL gene and found that it encodes a protein with sequence similarity to both the human sterol reductase family and yeast C-14 sterol reductase and is preferentially expressed in actively growing cells. Biochemical analysis indicates that the fk-J79 mutation results in deficient C-14 sterol reductase activity, abnormal sterol composition, and reduction of brassinosteroids (BRs). Unlike other BR-deficient mutants, the defect of hypocotyl elongation in fk-J79 cannot be corrected by exogenous BRs. The unique phenotypes and sterol composition in fk-J79 indicate crucial roles of sterol regulation and signaling in cell division and cell expansion in embryonic and post-embryonic development in plants.
authors.affiliation: Department of Horticulture and Crop Science, The Ohio State University, Columbus, Ohio 43210 USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Jang
authors.forename: S
authors.initials: S
authors.lastname: Fujioka
authors.forename: M
authors.initials: M
authors.lastname: Tasaka
authors.forename: H
authors.initials: H
authors.lastname: Seto
authors.forename: S
authors.initials: S
authors.lastname: Takatsuto
authors.forename: A
authors.initials: A
authors.lastname: Ishii
authors.forename: M
authors.initials: M
authors.lastname: Aida
authors.forename: S
authors.initials: S
authors.lastname: Yoshida
authors.forename: J
authors.initials: J
authors.lastname: Sheen
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000196:embryology* / Q000235:genetics*; D019521:Body Patterning; D002455:Cell Division / Q000235:genetics; D003001:Cloning, Molecular; D005656:Fungal Proteins / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D018546:Hypocotyl / Q000235:genetics; D018519:Meristem / Q000235:genetics / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D009154:Mutation; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics; D010641:Phenotype; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000235:genetics; D013261:Sterols / Q000096:biosynthesis* / Q000737:chemistry; D013997:Time Factors; D015003:Yeasts / Q000201:enzymology; D000097682:Lamin B Receptor
chemical_list: D005656:Fungal Proteins; D010088:Oxidoreductases; D018160:Receptors, Cytoplasmic and Nuclear; D013261:Sterols; D000097682:Lamin B Receptor; C022672:delta(14)-sterol reductase