FACKEL is a sterol C-14 reductase required for organized cell division and expansion in Arabidopsis embryogenesis

• Published in: Genes & development 2000-06, Vol.14 (12), p.1471-1484
• Main Authors: Schrick, K, Mayer, U, Horrichs, A, Kuhnt, C, Bellini, C, Dangl, J, Schmidt, J, Jürgens, G
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Arabidopsis - embryology; Arabidopsis - enzymology; Arabidopsis thaliana; Base Sequence; brassinosteroids; Cell Division; Cloning, Molecular; DNA, Complementary - metabolism; erg24 gene; Exons; FACKEL gene; Gas Chromatography-Mass Spectrometry; Genetic Complementation Test; In Situ Hybridization; lamin B receptors; Life Sciences; Membrane Proteins - genetics; Molecular Sequence Data; Mutation; Oxidoreductases - metabolism; Phenotype; Phylogeny; Plant Proteins - genetics; Plant Proteins - physiology; Polymorphism, Restriction Fragment Length; Research Paper; RNA, Messenger - metabolism; Signal Transduction; sterol; sterol C-14 reductase; Time Factors; Transcription, Genetic
• ISSN: 0890-9369; 1549-5477; 1549-5477
• DOI: 10.1101/gad.14.12.1471

In flowering plants, the developing embryo consists of growing populations of cells whose fates are determined in a position-dependent manner to form the adult organism. Mutations in the FACKEL (FK) gene affect body organization of the Arabidopsis seedling. We report that FK is required for cell division and expansion and is involved in proper organization of the embryo. We isolated FK by positional cloning. Expression analysis in embryos revealed that FK mRNA becomes localized to meristematic zones. FK encodes a predicted integral membrane protein related to the vertebrate lamin B receptor and sterol reductases across species, including yeast sterol C-14 reductase ERG24. We provide functional evidence that FK encodes a sterol C-14 reductase by complementation of erg24. GC/MS analysis confirmed that fk mutations lead to accumulation of intermediates in the biosynthetic pathway preceding the C-14 reductase step. Although fk represents a sterol biosynthetic mutant, the phenotype was not rescued by feeding with brassinosteroids (BRs), the only plant sterol signaling molecules known so far. We propose that synthesis of sterol signals in addition to BRs is important in mediating regulated cell growth and organization during embryonic development. Our results indicate a novel role for sterols in the embryogenesis of plants.