Flowering; Vernalization; FLOWERING LOCUS C; Sinapis alba; Brassicaceae
Abstract :
[en] In many plants, flowering is promoted by a long exposure to cold, a process known as ‘vernalisation’. In Arabidopsis, the vernalisation pathway was shown to promote flowering via the repression of the FLOWERING LOCUS C (FLC) gene, which encodes a repressor of flowering.
As far as we know, the genetical control of flowering is conserved among Brassicaceae, and we reported elsewhere cloning of flowering times genes of the photoperiodic pathway in Sinapis alba, based on sequence similarity with Arabidopsis. However, little is known about vernalisation in Sinapis. We therefore undertook a physiological and molecular study of this process.
Plants of Sinapis were grown in non inductive short days and vernalised at 7°C, at the seedling stage. Vernalisation was found to accelerate flowering and an increasing effect was observed for vernalisation treatments longer than 2 weeks. We cloned an FLC-like sequence (SaFLC) by screening a cDNA library, and used it as a probe to perform expression analyses. We observed that SaFLC was almost completely repressed after 1 week of vernalisation, but repression was stable only after 2 weeks, which is consistent with the fact that 2-week is the minimal duration of vernalisation that promotes flowering. Hence the molecular mechanisms of vernalisation seem to be conserved in Sinapis and Arabidopsis.