title: NO FLOWERING IN SHORT DAY (NFL) is a bHLH transcription factor that promotes flowering specifically under short-day conditions in Arabidopsis.
abstract: Flowering in plants is a dynamic and synchronized process where various cues including age, day length, temperature and endogenous hormones fine-tune the timing of flowering for reproductive success. Arabidopsis thaliana is a facultative long day (LD) plant where LD photoperiod promotes flowering. Arabidopsis still flowers under short-day (SD) conditions, albeit much later than in LD conditions. Although factors regulating the inductive LD pathway have been extensively investigated, the non-inductive SD pathway is much less understood. Here, we identified a key basic helix-loop-helix transcription factor called NFL (NO FLOWERING IN SHORT DAY) that is essential to induce flowering specifically under SD conditions in Arabidopsis. nfl mutants do not flower under SD conditions, but flower similar to the wild type under LD conditions. The no-flowering phenotype in SD is rescued either by exogenous application of gibberellin (GA) or by introducing della quadruple mutants in the nfl background, suggesting that NFL acts upstream of GA to promote flowering. NFL is expressed at the meristematic regions and NFL is localized to the nucleus. Quantitative RT-PCR assays using apical tissues showed that GA biosynthetic genes are downregulated and the GA catabolic and receptor genes are upregulated in the nfl mutant compared with the wild type, consistent with the perturbation of the endogenous GA biosynthetic and catabolic intermediates in the mutant. Taken together, these data suggest that NFL is a key transcription factor necessary for promotion of flowering under non-inductive SD conditions through the GA signaling pathway.
authors.affiliation: Department of Molecular Biosciences and The Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Nidhi
authors.initials: N
authors.lastname: Sharma
authors.affiliation: Department of Molecular Biosciences and The Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Ruijiao
authors.initials: R
authors.lastname: Xin
authors.affiliation: Department of Molecular Biosciences and The Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Dong-Hwan
authors.initials: DH
authors.lastname: Kim
authors.affiliation: Department of Molecular Biosciences and The Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Sibum
authors.initials: S
authors.lastname: Sung
authors.affiliation: Institute of Plant Biology, Department of Plant Physiology and Biochemistry, Technical University of Braunschweig, Braunschweig D-38106, Germany.
authors.forename: Theo
authors.initials: T
authors.lastname: Lange
authors.affiliation: Department of Molecular Biosciences and The Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712, USA huq@austin.utexas.edu.
authors.forename: Enamul
authors.initials: E
authors.lastname: Huq
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D003080:Cold Temperature; D004843:Epistasis, Genetic / Q000187:drug effects; D035264:Flowers / Q000187:drug effects / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005816:Genetic Complementation Test; D005875:Gibberellins / Q000096:biosynthesis / Q000378:metabolism / Q000494:pharmacology; D018519:Meristem / Q000187:drug effects / Q000378:metabolism; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D009928:Organ Specificity / Q000187:drug effects / Q000235:genetics; D010641:Phenotype; D017440:Photoperiod; D021381:Protein Transport / Q000187:drug effects; D060888:Real-Time Polymerase Chain Reaction; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D005875:Gibberellins; C000608947:NFL protein, Arabidopsis
keywords: Arabidopsis; BHLH transcription factor; Flowering time; GA signaling pathway; Photoperiod pathway