title: The ABA1 gene and carotenoid biosynthesis are required for late skotomorphogenic growth in Arabidopsis thaliana.
abstract: Several plant hormones, including auxin, brassinosteroids and gibberellins, are required for skotomorphogenesis, which is the etiolated growth that seedlings undergo in the absence of light. To examine the growth of abscisic acid (ABA)-deficient mutants in the dark, we analysed several aba1 loss-of-function alleles, which are deficient in zeaxanthin epoxidase. The aba1 mutants displayed a partially de-etiolated phenotype, including reduced hypocotyl growth, cotyledon expansion and the development of true leaves, during late skotomorphogenic growth. In contrast, only small differences in hypocotyl growth were found between wild-type seedlings and ABA-deficient mutants impaired in subsequent steps of the pathway, namely nced3, aba2, aba3 and aao3. Interestingly, phenocopies of the partially de-etiolated phenotype of the aba1 mutants were obtained when wild-type seedlings were dark-grown on medium supplemented with fluridone, an inhibitor of phytoene desaturase, and hence, of carotenoid biosynthesis. ABA supplementation did not restore the normal skotomorphogenic growth of aba1 mutants or fluridone-treated wild-type plants, suggesting a direct inhibitory effect of fluridone on carotenoid biosynthesis. In addition, aba1 mutants showed impaired production of the beta-carotene-derived xanthophylls, neoxanthin, violaxanthin and antheraxanthin. Because fluridone treatment of wild-type plants phenocopied the phenotype of dark-grown aba1 mutants, impaired carotenoid biosynthesis in aba1 mutants is probably responsible for the observed skotomorphogenic phenotype. Thus, ABA1 is required for skotomorphogenic growth, and beta-carotene-derived xanthophylls are putative regulators of skotomorphogenesis.
authors.affiliation: División de Genética and Instituto de Bioingeniería, Universidad Miguel Hernández, Campus de Elche, 03202 Elche, Alicante, Spain.
authors.forename: José María
authors.initials: JM
authors.lastname: Barrero
authors.forename: Pedro L
authors.initials: PL
authors.lastname: Rodríguez
authors.forename: Víctor
authors.initials: V
authors.lastname: Quesada
authors.forename: David
authors.initials: D
authors.lastname: Alabadí
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Blázquez
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Boutin
authors.forename: Annie
authors.initials: A
authors.lastname: Marion-Poll
authors.forename: María Rosa
authors.initials: MR
authors.lastname: Ponce
authors.forename: José Luis
authors.initials: JL
authors.lastname: Micol
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002338:Carotenoids / Q000096:biosynthesis* / Q000737:chemistry; D003624:Darkness; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D018546:Hypocotyl / Q000187:drug effects / Q000254:growth & development; D009154:Mutation / Q000235:genetics; D010088:Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D010641:Phenotype; D011728:Pyridones / Q000494:pharmacology
chemical_list: D029681:Arabidopsis Proteins; D011728:Pyridones; D002338:Carotenoids; C013351:fluridone; D000040:Abscisic Acid; D010088:Oxidoreductases; C097153:zeaxanthin epoxidase