title: GIGANTEA directly activates Flowering Locus T in Arabidopsis thaliana.
abstract: Plants perceive environmental signals such as day length and temperature to determine optimal timing for the transition from vegetative to floral stages. Arabidopsis flowers under long-day conditions through the CONSTANS (CO)-FLOWERING LOCUS T (FT) regulatory module. It is thought that the environmental cues for photoperiodic control of flowering are initially perceived in the leaves. We have previously shown that GIGANTEA (GI) regulates the timing of CO expression, together with FLAVIN-BINDING, KELCH REPEAT, F BOX protein 1. Normally, CO and FT are expressed exclusively in vascular bundles, whereas GI is expressed in various tissues. To better elucidate the role of tissue-specific expression of GI in the flowering pathway, we established transgenic lines in which GI is expressed exclusively in mesophyll, vascular bundles, epidermis, shoot apical meristem, or root. We found that GI expressed in either mesophyll or vascular bundles rescues the late-flowering phenotype of the gi-2 loss-of-function mutant under both short-day and long-day conditions. Interestingly, GI expressed in mesophyll or vascular tissues increases FT expression without up-regulating CO expression under short-day conditions. Furthermore, we examined the interaction between GI and FT repressors in mesophyll. We found that GI can bind to three FT repressors: SHORT VEGETATIVE PHASE (SVP), TEMPRANILLO (TEM)1, and TEM2. Finally, our chromatin immunoprecipitation experiments showed that GI binds to FT promoter regions that are near the SVP binding sites. Taken together, our data further elucidate the multiple roles of GI in the regulation of flowering time.
authors.affiliation: Section of Cell and Developmental Biology, Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093-0130, USA.
authors.forename: Mariko
authors.initials: M
authors.lastname: Sawa
authors.forename: Steve A
authors.initials: SA
authors.lastname: Kay
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000502:physiology; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology; D035264:Flowers / Q000254:growth & development; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D009154:Mutation; D010641:Phenotype; D017440:Photoperiod; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000502:physiology; D012098:Reproduction / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction; D014018:Tissue Distribution; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology
chemical_list: D029681:Arabidopsis Proteins; C092776:CONSTANS protein, Arabidopsis; D004268:DNA-Binding Proteins; C410504:FKF1 protein, Arabidopsis; C418905:FT protein, Arabidopsis; C121183:GI protein, Arabidopsis; D012333:RNA, Messenger; D018749:RNA, Plant; D012097:Repressor Proteins; C407549:SVP protein, Arabidopsis; C533191:TEM1 protein, Arabidopsis; D014157:Transcription Factors