title: Multifunctional acetyl-CoA carboxylase 1 is essential for very long chain fatty acid elongation and embryo development in Arabidopsis.
abstract: Acetyl-CoA carboxylase (ACCase) catalyses the carboxylation of acetyl-CoA, forming malonyl-CoA, which is used in the plastid for fatty acid synthesis and in the cytosol in various biosynthetic pathways including fatty acid elongation. In Arabidopsis thaliana, ACC1 and ACC2, two genes located in a tandem repeat within a 25-kbp genomic region near the centromere of chromosome 1, encode two multifunctional ACCase isoforms. Both genes, ACC1 and ACC2, appear to be ubiquitously expressed, but little is known about their respective function and importance. Here, we report the isolation and characterisation of two allelic mutants disrupted in the ACC1 gene. Both acc1-1 and acc1-2 mutations are recessive and embryo lethal. Embryo morphogenesis is impaired and both alleles lead to cucumber-like structures lacking in cotyledons, while the shortened hypocotyl and root exhibit a normal radial pattern organisation of the body axis. In this abnormal embryo, the maturation process still occurs. Storage proteins accumulate normally, while triacylglycerides (TAG) are synthesised at a lower concentration than in the wild-type seed. However, these TAG are totally devoid of very long chain fatty acids (VLCFA) and consequently enriched in C18:1, like all lipid fractions analysed in the mutant seed. These data demonstrate, in planta, the role of ACCase 1 in VLCFA elongation. Furthermore, this multifunctional enzyme also plays an unexpected and central function in embryo morphogenesis, especially in apical meristem development.
authors.affiliation: Unité de Biologie des Semences, INRA, RD 10, 78026 Versailles Cedex, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Baud
authors.forename: Virginie
authors.initials: V
authors.lastname: Guyon
authors.forename: Jocelyne
authors.initials: J
authors.lastname: Kronenberger
authors.forename: Sylvie
authors.initials: S
authors.lastname: Wuillème
authors.forename: Martine
authors.initials: M
authors.lastname: Miquel
authors.forename: Michel
authors.initials: M
authors.lastname: Caboche
authors.forename: Loïc
authors.initials: L
authors.lastname: Lepiniec
authors.forename: Christine
authors.initials: C
authors.lastname: Rochat
mesh_terms: D000103:Acetyl-CoA Carboxylase / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D018744:DNA, Plant / Q000235:genetics / Q000302:isolation & purification; D035264:Flowers / Q000235:genetics / Q000502:physiology; D005804:Genes, Lethal; D005808:Genes, Recessive; D016133:Polymerase Chain Reaction; D012639:Seeds / Q000502:physiology
chemical_list: D029681:Arabidopsis Proteins; D018744:DNA, Plant; D000103:Acetyl-CoA Carboxylase