title: Sugar and ABA responsiveness of a minimal RBCS light-responsive unit is mediated by direct binding of ABI4.
abstract: Photosynthesis-associated nuclear genes (PhANGs) are able to respond to multiple environmental and developmental signals, including light, sugars and abscisic acid (ABA). PhANGs have been extensively studied at the level of transcriptional regulation and several cis-acting elements important for light responsiveness have been identified in their promoter sequences. However, the regulatory elements involved in sugar and ABA regulation of PhANGs have not been completely characterized. Using conserved modular arrangement 5 (CMA5), a previously characterized minimal light-responsive unit, we show that in Arabidopsis thaliana this unit responds not only positively to light signals, but also negatively to sugars and ABA. The latter responses were found to be impaired in the abi4 mutant, indicating that ABSCISIC ACID INSENSITIVE-4 (ABI4) is a regulator involved in sugar and ABA repression of this minimal regulatory unit. Furthermore, we report a new sequence element conserved in several rbcS promoters, herewith named S-box, which is important for the sugar and ABA responsiveness of CMA5. This sequence corresponds to a putative ABI4-binding site, which is in fact bound by the Arabidopsis ABI4 protein in vitro. The S-box is closely associated with the G-box present in CMA5, and this association is conserved in the promoters of several RBCS genes. This phylogenetically conserved promoter feature probably reflects a common regulatory mechanism and identifies a point of convergence between light- and sugar-signaling pathways.
authors.affiliation: Departamento de Ingeniería Genética de Plantas, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional - Unidad Irapuato, Apartado Postal 629, Irapuato, Guanajuato 36500, Mexico.
authors.forename: Gustavo Javier
authors.initials: GJ
authors.lastname: Acevedo-Hernández
authors.forename: Patricia
authors.initials: P
authors.lastname: León
authors.forename: Luis Rafael
authors.initials: LR
authors.lastname: Herrera-Estrella
mesh_terms: D000040:Abscisic Acid / Q000502:physiology*; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism / Q000502:physiology*; D001483:Base Sequence; D001665:Binding Sites; D002241:Carbohydrates / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D008027:Light; D008969:Molecular Sequence Data; D010788:Photosynthesis / Q000502:physiology; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012273:Ribulose-Bisphosphate Carboxylase / Q000502:physiology*; D012689:Sequence Homology, Nucleic Acid; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: C470421:ABI4 protein, Arabidopsis; D029681:Arabidopsis Proteins; D002241:Carbohydrates; D014157:Transcription Factors; D000040:Abscisic Acid; D012273:Ribulose-Bisphosphate Carboxylase