title: Hahb-10, a sunflower homeobox-leucine zipper gene, is regulated by light quality and quantity, and promotes early flowering when expressed in Arabidopsis.
abstract: Homeodomain-leucine zipper proteins constitute a family of transcription factors found only in plants. Expression patterns of the sunflower homeobox-leucine zipper gene Hahb-10 (Helianthus annuus homeobox-10), that belongs to the HD-Zip II subfamily, were analysed. Northern blots showed that Hahb-10 is expressed primarily in mature leaves, although expression is clearly detectable in younger leaves and also in stems. Considerably higher expression levels were detected in etiolated seedlings compared with light-grown seedlings. Induction of Hahb-10 expression was observed when seedlings were subjected to treatment with gibberellins. Transgenic Arabidopsis thaliana plants that express Hahb-10 under the 35S cauliflower mosaic virus promoter show special phenotypic characteristics such as darker cotyledons and planar leaves. A reduction in the life cycle of about 25% allowing earlier seed collection was also observed, and this phenomenon is clearly related to a shortened flowering time. When the number of plants per pot increased, the difference in developmental rate between transgenic and non-transformed individuals became larger. After gibberellin treatment, the relative difference in life cycle duration was considerably reduced. Several light-regulated genes have been tested as possible target genes of Hahb-10. One of them, PsbS, shows a different response to illumination conditions in transgenic plants compared with the response in wild-type plants while the other genes behave similarly in both genotypes. We propose that Hahb-10 functions in a signalling cascade(s) that control(s) plant responses to light quality and quantity, and may also be involved in gibberellin transduction pathways.
authors.affiliation: Cátedra de Biología Celular y Molecular, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, CC 242 Paraje El Pozo, 3000 Santa Fe, Argentina.
authors.forename: Eva C
authors.initials: EC
authors.lastname: Rueda
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Dezar
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Gonzalez
authors.forename: Raquel L
authors.initials: RL
authors.lastname: Chan
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D015152:Blotting, Northern; D018744:DNA, Plant / Q000235:genetics; D035263:Flowering Tops / Q000254:growth & development*; D018506:Gene Expression Regulation, Plant; D005801:Genes, Homeobox; D017343:Genes, Plant; D005875:Gibberellins / Q000494:pharmacology; D006368:Helianthus / Q000235:genetics* / Q000502:physiology; D016350:Leucine Zippers; D008027:Light; D010641:Phenotype; D018515:Plant Leaves / Q000737:chemistry / Q000502:physiology; D010940:Plant Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology; D018547:Plant Stems / Q000737:chemistry / Q000502:physiology; D030821:Plants, Genetically Modified; D018749:RNA, Plant / Q000235:genetics
chemical_list: D018744:DNA, Plant; D005875:Gibberellins; D010940:Plant Proteins; D018749:RNA, Plant