As you may know, there are three main pathways important in the regulation of flowering time in the model plant Arabidopsis thaliana. The photo period pathway, the autonomous pathway and the vernalization pathway. These pathways converge to regulate the expression of one or more of the three genes that promote flowering: SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1), FLOWERING LOCUS T (FT) or LEAFY (LFY).The photo period pathway promotes flowering when the days are long and activates the expression of SOC1 through regulation of the FT gene. While the autonomous pathway and the vernalization pathway both down regulate the expression of the MADS domain protein, FLOWERING LOCUS C (FLC) and promote flowering by releasing SOC1 from the repression of FLC.
In 2006 another flowering time gene in Arabidopsis was discovered by Bouveret. R. et al.[1], called MSI1. Physiologically MSI1 is similar to genes of the autonomous pathway and is homologous to the MS14/FVE pathway, however it activates flowering independently of FLC. Instead MSI1 is needed to modify the SOC1 chromatin to express high levels of SOC1, which induces flowering. In plants with mutant MSI1 the speed at which SOC1 is transcribed and processed is delayed and so plants that express low levels of MSI1 flower late while plants that over express MSI1 flower early. Therefore the regulation of flowering time relies not only on the correct expression of FLC but also on the correct expression of the SOC1 chromatin.
Andrew Basson (41197024)
Reference
Bouveret R, Schönrock N, Gruissem W and Hennig L (2006), Regulation of flowering time by Arabidopsis MSI1, Development 133, 1693-1702
