title: SRR1 is essential to repress flowering in non-inductive conditions in Arabidopsis thaliana.
abstract: Timing of flowering is determined by environmental and developmental signals, leading to promotion or repression of key floral integrators. SENSITIVITY TO RED LIGHT REDUCED (SRR1) is a pioneer protein previously shown to be involved in regulation of the circadian clock and phytochrome B signalling in Arabidopsis thaliana. This report has examined the role of SRR1 in flowering time control. Loss-of-function srr1-1 plants flowered very early compared with the wild type under short-day conditions and had a weak flowering response to increasing daylength. Furthermore, FLOWERING LOCUS T (FT) transcript levels were elevated already in short days in srr1-1 compared with the wild type. This correlated with elevated end of day levels of CONSTANS (CO), whereas levels of CYCLING DOF FACTOR 1 (CDF1), a repressor of CO transcription, were reduced. srr1-1 gi-2 and srr1-1 co-9 double mutants showed that SRR1 can also repress flowering independently of the photoperiodic pathway. srr1-1 flowered consistently early between 16 °C and 27 °C, showing that SRR1 prevents premature flowering over a wide temperature range. SRR1 also promotes expression of the repressors TEMPRANILLO 1 (TEM1) and TEM2. Consequently their targets in the gibberellin biosynthesis pathway were elevated in srr1-1. SRR1 is thus an important focal point of both photoperiodic and photoperiod-independent regulation of flowering. By stimulating expression of the FT-binding repressors CDF1, TEM1 and TEM2, and FLC, flowering is inhibited in non-inductive conditions.
authors.affiliation: Molecular Cell Physiology, Faculty for Biology, Bielefeld University, Bielefeld, Germany dorothee.staiger@uni-bielefeld.de mikael.johansson@uni-bielefeld.de.
authors.forename: Mikael
authors.initials: M
authors.lastname: Johansson
authors.affiliation: Molecular Cell Physiology, Faculty for Biology, Bielefeld University, Bielefeld, Germany dorothee.staiger@uni-bielefeld.de mikael.johansson@uni-bielefeld.de.
authors.forename: Dorothee
authors.initials: D
authors.lastname: Staiger
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000502:physiology / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D057906:Circadian Clocks; D035264:Flowers / Q000235:genetics* / Q000502:physiology / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant; D008027:Light; D009154:Mutation; D010641:Phenotype; D017440:Photoperiod; D030821:Plants, Genetically Modified; D012098:Reproduction; D015398:Signal Transduction; D013997:Time Factors
chemical_list: D029681:Arabidopsis Proteins; C511730:SRR1 protein, Arabidopsis
keywords: Arabidopsis; SRR1.; circadian clock; flowering time control; photoperiod; repressors