title: HvMCB1, a R1MYB transcription factor from barley with antagonistic regulatory functions during seed development and germination.
abstract: The functional analysis of hydrolase gene promoters induced by gibberellin (GA) in barley aleurone cells upon germination has identified a tripartite GA-response complex (GARC) containing a 5'-TATCCAC-3' box as well as the GA-responsive element (GARE) recognized by GAMYB and the pyrimidine box interacting with the DOF transcription factors BPBF and SAD. We show here that the MCB1 gene encoding a R1MYB protein binds to the 5'-TATCCAC-3' (GATA core) box in vitro and is a transcriptional repressor of a GA-induced amylase (Amy6.4) promoter in bombarded aleurone layers. Northern blot and mRNA in situ hybridization analyses showed that the MCB1 transcripts accumulate in the aleurone cells upon germination, as well as in endosperm tissues during seed development. The HvMCB1 protein expressed in bacteria binds in a specific manner to a 27-mer oligonucleotide containing the 5'-TATCCAC-3' sequence, derived from the promoter region of the Amy6.4 gene. Accumulation of the MCB1 transcript diminished in response to external GA incubation in aleurone cells, and in transient expression experiments HvMCB1 repressed transcription of the Amy6.4 promoter in GA-treated aleurone layers and reversed the GAMYB-mediated activation of this amylase promoter. In contrast, during endosperm maturation HvMCB1 acted as a transcription activator of the seed-specific Itr1 gene promoter through binding to a 5'-GATAAGATA-3' box.
authors.affiliation: Laboratorio de Bioquímica y Biología Molecular. Dpto. de Biotecnología-UPM, ETSI Agrónomos, 28040 Madrid, Spain.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Rubio-Somoza
authors.forename: Manuel
authors.initials: M
authors.lastname: Martinez
authors.forename: Isabel
authors.initials: I
authors.lastname: Diaz
authors.forename: Pilar
authors.initials: P
authors.lastname: Carbonero
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D002467:Cell Nucleus / Q000378:metabolism; D018744:DNA, Plant; D024202:Electrophoretic Mobility Shift Assay; D018525:Germination; D001467:Hordeum / Q000196:embryology / Q000378:metabolism* / Q000502:physiology; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011401:Promoter Regions, Genetic; D012639:Seeds / Q000254:growth & development*; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D018744:DNA, Plant; D010940:Plant Proteins; D014157:Transcription Factors