The Arabidopsis E3 Ubiquitin Ligase HOS1 Negatively Regulates CONSTANS Abundance in the Photoperiodic Control of Flowering

• Published in: The Plant cell Vol. 24; no. 3; pp. 982 - 999
• Main Authors: Lazaro, Ana, Valverde, Federico, Piñeiro, Manuel, Jarillo, Jose A.
• Format: Journal Article
• Language: English
• Published: England American Society of Plant Physiologists 01.03.2012; American Society of Plant Biologists
• Subjects: Arabidopsis - enzymology; Arabidopsis - genetics; Arabidopsis - physiology; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Flowering; Flowers - genetics; Flowers - physiology; Gene expression regulation; Gene Expression Regulation, Plant; Genetic mutation; Intracellular Signaling Peptides and Proteins - genetics; Intracellular Signaling Peptides and Proteins - metabolism; Leaves; Mutation; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; Phenotypes; Photoperiod; Plant cells; Plants; Proteins; Transcription Factors - genetics; Transcription Factors - metabolism; Ubiquitins
• ISSN: 1040-4651; 1532-298X
• DOI: 10.1105/tpc.110.081885

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 GENESI (HOS1) locus, which encodes a RING finger-containing E3 ubiquitin ligase. The esd6/hos1 mutation causes decreased FLOWERING LOCUS 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.