title: GA4 is the active gibberellin in the regulation of LEAFY transcription and Arabidopsis floral initiation.
abstract: Flower initiation in Arabidopsis thaliana under noninductive short-day conditions is dependent on the biosynthesis of the plant hormone gibberellin (GA). This dependency can be explained, at least partly, by GA regulation of the flower meristem identity gene LEAFY (LFY) and the flowering time gene SUPPRESSOR OF CONSTANS1. Although it is well established that GA(4) is the active GA in the regulation of Arabidopsis shoot elongation, the identity of the GA responsible for the regulation of Arabidopsis flowering has not been established. Through a combination of GA quantifications and sensitivity assays, we show that GA(4) is the active GA in the regulation of LFY transcription and Arabidopsis flowering time under short-day conditions. The levels of GA(4) and sucrose increase dramatically in the shoot apex shortly before floral initiation, and the regulation of genes involved in GA metabolism suggests that this increase is possibly due to transport of GAs and sucrose from outside sources to the shoot apex. Our results demonstrate that in the dicot Arabidopsis, in contrast with the monocot Lolium temulentum, GA(4) is the active GA in the regulation of both shoot elongation and flower initiation.
authors.affiliation: Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, S-90183 Umeå, Sweden.
authors.forename: Sven
authors.initials: S
authors.lastname: Eriksson
authors.forename: Henrik
authors.initials: H
authors.lastname: Böhlenius
authors.forename: Thomas
authors.initials: T
authors.lastname: Moritz
authors.forename: Ove
authors.initials: O
authors.lastname: Nilsson
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D035264:Flowers / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D005875:Gibberellins / Q000145:classification / Q000378:metabolism / Q000502:physiology*; D005966:Glucuronidase / Q000032:analysis; D008027:Light; D017440:Photoperiod; D011993:Recombinant Fusion Proteins / Q000032:analysis; D013395:Sucrose / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D005875:Gibberellins; C074747:LFY protein, Arabidopsis; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D013395:Sucrose; C007842:gibberellic acid; D005966:Glucuronidase