GMOF: Genetic and molecular control of the transition to flowering

• Unité de recherche: PCRD EU
• Numéro de projet: 96.0425
• Titre du projet anglais: GMOF: Genetic and molecular control of the transition to flowering

Mots-clé (Anglais)

Flowering time; vernalization; photoperiod; arabidopsis; transcription factors

Autre Numéro de projet (Anglais)

EU project number: BIO4CT972340

Programme de recherche (Anglais)

EU-programme: 4. Frame Research Programme - 4.1 Biotechnology

Description succincte (Anglais)

See abstract

Partenaires et organisations internationales (Anglais)

Coordinator: Amica-Science-EEIG (UK)

Résumé des résultats (Abstract) (Anglais)

Our aim during the GMOF project was to study the role of the MADSA/AGL20, MADSB/AGL8, and FPF1 genes of Arabidopsis in the floral transition. Overexpression of each gene under the control of the 35S CaMV promoter leads to earlier flowering in the transgenic plants, indicating that the genes are involved in the regulation of flowering time.
Transposon insertion mutants of AGL20 have been identified by a PCR screen. For three independent transposon insertion lines we could show that the agl20 mutants are later flowering both under short and long day conditions, indicating an important role for agl20 for the floral transition. By expression analysis we could show that the AGL20 gene is regulated by CO, GI and FCA as well as by gibberellins (GAs), indicating that this gene is activated by several flowering promoting pathways and might play a role in converging different flowering signals at the apical meristem.
The phenotype of FPF1 overexpressing plants resembles that of plants treated with GAs. Inhibiting GA biosynthesis with paclobutrazol and a subsequent treatment with GAs had shown that the transgenic plants are more responsive to GAs than wild type. We have compared GAs in apical buds of transgenic and wild type plants and could show that the amount of GAs are reduced in 35S::FPF1 plants under short day conditions. Since we could also show that the gibberellin insensitive mutant (gai) is epistatic to FPF1, we conclude that FPF1 is involved in GA signalling in the apical neristem during the transition to flowering.
In order to further understand FPF1 function we have taken a differential display approach to isolate other transcripts whose expression is altered in apices of transgenic FPF1 plants. Samples compared were from apices of wild type plants and FPF1 overexpressing plants before and after floral induction. A differential clone was isolated, which is significantly down-regulated in a FPF1 overexpressing background. Quantitative RT-PCR and northern blot analysis confirmed the downregulation of this gene which also responds to GA treatments with decreased expression levels. Overexpression of this gene leads to earlier flowering whereas with antisense approaches we have observed a delay in flowering time, indicating that we have identified a new flowering time gene that might interact with FPF1.
In addition the genes for MADSA and FPF1 have been isolated and sequenced and 2.5 kb of the promoters have been fused to the GUS gene and transformed into Arabidopsis. We have obtained transgenic plants with promoter constructs that can be used for a further characterisation of the regulation of the genes in response to floral induction in different genetic backgrounds.

Références bases de données (Anglais)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 96.0425