Post-translational regulation of FLC is mediated by an E3 ubiquitin ligase activity of SINAT5 in Arabidopsis

Suppression of Flowering Locus C (FLC) is critical for the transition from the vegetative to reproductive phase in Arabidopsis. FLC represses the expression of several genes involved in floral induction and its transcription is positively or negatively regulated by FRIGIDA or by vernalization, respectively. However, the regulatory mechanisms for the level and stability of FLC protein throughout development are unknown. Here, we show that SINAT5 colocalizes with FLC in the nuclear bodies and that its zinc finger motif interacts directly with the MADS-box domain of FLC. In addition, it is shown that SINAT5 has an E3 ubiquitin ligase activity towards FLC as a substrate, suggesting that SINAT5 participates in the regulation of flowering time through the ubiquitin-mediated proteolysis of FLC.