Isolation and analysis of a putative FLC orthologue in Sinapis alba L.

In many plant species, flowering is promoted by a long exposure to low temperature, a process known as vernalization. Some plants even have an absolute requirement for winter cold before being able to flower the next summer, hence behave as biennials or winter crops.
A recent breakthrough in the understanding of the molecular bases of vernalization has been the cloning of the FLOWERING LOCUS C (FLC) gene in Arabidopsis thaliana (Michaels S.D. & Amasino R.M., 1999). FLC encodes a repressor of flowering and is downregulated by vernalization. So vernalization relieves the inhibitory role that FLC plays on downstream genes involved in the floral transition of the shoot apical meristem (SAM).

Although vernalization has been shown, by physiological studies, to be sensed by the SAM, molecular evidences are missing. Such analyses are impaired in Arabidopsis by the small size of the plant and the rosette growth habit. We therefore cloned a FLC homologue in a caulescent relative Brassicaceae: mustard (Sinapis alba L.). We identified two clones by screening a cDNA library made from leaf mRNA. One of them, SaFLC1, was used for in situ hybridizations on SAM sections. Preliminary results are shown.

Because of its agronomical importance, we have also tried to manipulate the vernalization process in crops. By using a transgenic approach, we have attempted to bypass the strict vernalization requirement of winter colza (Brassica napus L.). We have over-expressed SaMADS A, a gene which is repressed by FLC in wild type, and observed that the transgenics did not require vernalization any more.