title: Thermoperiodic Control of Floral Induction Involves Modulation of the Diurnal FLOWERING LOCUS T Expression Pattern.
abstract: Thermoperiodism is defined as the ability to discriminate between day temperature (DT) and night temperature (NT). Our aim was to shed light on the mechanistic basis of thermoperiodic floral induction with acceleration under lower DT than NT compared with other DT-NT combinations at the same average daily temperature (ADT), a response exploited in temperate area greenhouses. Arabidopsis thaliana floral pathway mutants and a lhy circadian clock mutant as well as the expression of floral integrators and LHY (LATE ELONGATED HYPOCOTYL) were studied under different DT-NT combinations, all at the same ADT. We show that acceleration of floral induction under lower DT than NT is linked to increased FT expression early during the day and generally increased LFY expression preceding visible flower buds, compared with higher DT than NT or equal DT and NT. Consistent with FLOWERING LOCUS T (FT) action through LEAFY (LFY), time to floral transition in ft-1 and lfy-1 was similar under all treatments, in contrast to the situation for soc1-1, which behaved like the wild type (WT). The lhy-21 mutants did not discriminate between opposite DT-NT combinations, whereas LHY expression in the WT differed in these temperature regimes. This might suggest that LHY plays a role in thermoperiodic control of floral induction. We conclude that thermoperiodic control of floral transition is associated with modulation of the diurnal expression patterns of FT, with timing of temperature alteration being important rather than ADT.
authors.affiliation: Department of Plant and Environmental Sciences, Norwegian University of Life Sciences, Norway.
authors.forename: Micael
authors.initials: M
authors.lastname: Wendell
authors.affiliation: Department of Plant and Environmental Sciences, Norwegian University of Life Sciences, Norway.
authors.forename: Linda
authors.initials: L
authors.lastname: Ripel
authors.affiliation: Department of Plant Science and Research Institute for Agriculture and Life Sciences, and Plant Genomics and Breeding Institute, Seoul National University, Seoul, South Korea.
authors.forename: YeonKyeong
authors.initials: Y
authors.lastname: Lee
authors.affiliation: Department of Plant Sciences, Faculty of Biosciences, Norwegian University of Life Sciences, Ås, Norway.
authors.forename: Odd Arne
authors.initials: OA
authors.lastname: Rognli
authors.affiliation: Norwegian University of Life Sciences, Department of Mathematical Sciences and Technology,  Aas, Norway.
authors.forename: Sissel
authors.initials: S
authors.lastname: Torre
authors.affiliation: Department of Plant Sciences, Faculty of Biosciences, Norwegian University of Life Sciences, Ås, Norway.
authors.forename: Jorunn E
authors.initials: JE
authors.lastname: Olsen
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D035264:Flowers / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D013696:Temperature; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C418905:FT protein, Arabidopsis; C074747:LFY protein, Arabidopsis; D014157:Transcription Factors
keywords: Arabidopsis thaliana; Day temperature; Floral induction; Floral pathway genes; Night temperature; Thermoperiodism