title: The balance between CONSTANS and TEMPRANILLO activities determines FT expression to trigger flowering.
abstract: Seasonal changes in day length influence flowering time in many plant species. In Arabidopsis, flowering is accelerated by exposure to long day (LD). Those inductive photoperiods are perceived in leaves [1] and initiate a long-distance signaling mediated by CO and FT. CO is expressed in the phloem according to a circadian rhythm [2-4]. Only under LD does CO induce FT expression as high levels of CO in the evening coincide with the external light that stabilizes CO protein [4, 5]. Subsequently, FT protein travels through the phloem to the shoot apex where, together with FD, it initiates flowering [6-12]. Despite the photoperiodic induction, a mechanism of floral repression is needed to avoid precocious flowering. We show that TEMPRANILLO genes (TEM1 and TEM2) act as novel direct FT repressors. Molecular and genetic analyses suggest that a quantitative balance between the activator CO and the repressor TEM determines FT levels. Moreover, developmental TEM downregulation marks the timing of flowering, as it shifts the CO/TEM balance in favor of CO activity, allowing FT transcript to reach the threshold level required to trigger flowering. We envision that this might be a general mechanism between long-day plants to ensure a tight regulation of flowering time.
authors: Centre for Research in Agricultural Genomics, CSIC-IRTA-UAB, Jordi Girona 18, 08034 Barcelona, Spain.
authors: Cristina
authors: C
authors: Castillejo
authors: Soraya
authors: S
authors: Pelaz
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D035264:Flowers / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D005966:Glucuronidase / Q000032:analysis; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010641:Phenotype; D017440:Photoperiod; D030821:Plants, Genetically Modified / Q000254:growth & development; D011993:Recombinant Fusion Proteins / Q000032:analysis; D012045:Regulatory Sequences, Nucleic Acid; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; C092776:CONSTANS protein, Arabidopsis; D004268:DNA-Binding Proteins; C418905:FT protein, Arabidopsis; C117696:RAV2 protein, Arabidopsis; D011993:Recombinant Fusion Proteins; C533191:TEM1 protein, Arabidopsis; D014157:Transcription Factors; D005966:Glucuronidase