PHYTOMER · FT, a global regulator of plant flowering and architecture

The floral transition has been an excellent system to study the molecular basis of primordia fate determination in response to environmental conditions in plants. In Arabidopsis, long days result in the transcription of the potent floral stimulator FT in the leaves. Transport of FT protein to the SAM enables an interaction between FT and FD to occur. This interaction leads to the expression of floral homeotic genes, and the subsequent programming of primordia as flowers. On the other hand, it is critically important for the plant to have a system for counteracting the floral promoting effects of FT/FD in part of the shoot to maintain vegetative stem cells and indeterminacy. In Arabidopsis, this role is carried out by TFL1, which acts in combination with FD to repress expression of flowering genes. In addition to FD, there is a paralog of FD, FDP, which appears to have similar functions to FD and be partially redundant with FD in activity. FDP has a very similar expression pattern to FD, and will therefore be considered in parallel with FD. The main objectives of the research project described in this proposal are: on the one hand figuring out what the components required for the FT/FD/FDP signalling module are. For this purpose I shall screen mutagenised tfl1-1 plants since in the absence of TFL1 protein, FT activity is greatly enhanced and this plants therefore provide an excellent genetic system to search for additional factors that are required for FT signalling which might not be revealed in a wild-type situation where FT is usually limiting. Furthermore, I aim to know what the cis-elements determining FD/FDP expression are by using a series of transgenic plants containing deletions in FD and FDP promoters in order to characterise the elements within FD and FDP promoters which are essential for their activity. And I also aim to know what the target genes of FD and FDP transcription factors are using the ChIP on chip technology.