CONSTANS acts in the phloem to regulate a systemic signal that induces photoperiodic flowering of Arabidopsis.
Flower development at the shoot apex is initiated in response to environmental cues. Day length is one of the most important of these and is perceived in the leaves. A systemic signal, called the floral stimulus or florigen, is then transmitted from the leaves through the phloem and induces floral development at the shoot apex. Genetic analysis in Arabidopsis identified a pathway of genes required for the initiation of flowering in response to day length. The nuclear zinc-finger protein CONSTANS (CO) plays a central role in this pathway, and in response to long days activates the transcription of FT, which encodes a RAF-kinase-inhibitor-like protein. We show using grafting approaches that CO acts non-cell autonomously to trigger flowering. Although CO is expressed widely, its misexpression from phloem-specific promoters, but not from meristem-specific promoters, is sufficient to induce early flowering and complement the co mutation. The mechanism by which CO triggers flowering from the phloem involves the cell-autonomous activation of FT expression. Genetic approaches indicate that CO activates flowering through both FT-dependent and FT-independent processes, whereas FT acts both in the phloem and the meristem to trigger flowering. We propose that, partly through the activation of FT, CO regulates the synthesis or transport of a systemic flowering signal, thereby positioning this signal within the established hierarchy of regulatory proteins that controls flowering.
An
Hailong
H
Max Planck Institute for Plant Breeding, Carl von Linne Weg 10, D-50829 Cologne, Germany.
Roussot
Clotilde
C
Suárez-López
Paula
P
Corbesier
Laurent
L
Vincent
Coral
C
Piñeiro
Manuel
M
Hepworth
Shelley
S
Mouradov
Aidyn
A
Justin
Samuel
S
Turnbull
Colin
C
Coupland
George
G
D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D035264:Flowers / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D017403:In Situ Hybridization; D017440:Photoperiod; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D016335:Zinc Fingers
D029681:Arabidopsis Proteins; C092776:CONSTANS protein, Arabidopsis; D004268:DNA-Binding Proteins; C418905:FT protein, Arabidopsis; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors