title: The Arabidopsis E3 ubiquitin ligase HOS1 negatively regulates CONSTANS abundance in the photoperiodic control of flowering.
abstract: The Arabidopsis thaliana early in short days6 (esd6) mutant was isolated in a screen for mutations that accelerate flowering time. Among other developmental alterations, esd6 displays early flowering in both long- and short-day conditions. Fine mapping of the mutation showed that the esd6 phenotype is caused by a lesion in the high expression of osmotically responsive genes1 (HOS1) locus, which encodes a RING finger-containing E3 ubiquitin ligase. The esd6/hos1 mutation causes decreased flowering locus C expression and requires CONSTANS (CO) protein for its early flowering phenotype under long days. Moreover, CO and HOS1 physically interact in vitro and in planta, and HOS1 regulates CO abundance, particularly during the daylight period. Accordingly, hos1 causes a shift in the regular long-day pattern of expression of flowering locus T (FT) transcript, starting to rise 4 h after dawn in the mutant. In addition, HOS1 interacts synergistically with constitutive photomorphogenic1, another regulator of CO protein stability, in the regulation of flowering time. Taken together, these results indicate that HOS1 is involved in the control of CO abundance, ensuring that CO activation of FT occurs only when the light period reaches a certain length and preventing precocious flowering in Arabidopsis.
authors.affiliation: Centro de Biotecnología y Genómica de Plantas, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria-Universidad Politécnica de Madrid, 28223 Madrid, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Lazaro
authors.forename: Federico
authors.initials: F
authors.lastname: Valverde
authors.forename: Manuel
authors.initials: M
authors.lastname: Piñeiro
authors.forename: Jose A
authors.initials: JA
authors.lastname: Jarillo
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D035264:Flowers / Q000235:genetics / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D017440:Photoperiod; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C092776:CONSTANS protein, Arabidopsis; D004268:DNA-Binding Proteins; C418905:FT protein, Arabidopsis; C425768:HOS1 protein, Arabidopsis; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors