A critical role of sterols in embryonic patterning and meristem programming revealed by the fackel mutants of Arabidopsis thaliana.
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.
Jang
J C
JC
Department of Horticulture and Crop Science, The Ohio State University, Columbus, Ohio 43210 USA.
Fujioka
S
S
Tasaka
M
M
Seto
H
H
Takatsuto
S
S
Ishii
A
A
Aida
M
M
Yoshida
S
S
Sheen
J
J
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
D005656:Fungal Proteins; D010088:Oxidoreductases; D018160:Receptors, Cytoplasmic and Nuclear; D013261:Sterols; D000097682:Lamin B Receptor; C022672:delta(14)-sterol reductase