The transition from vegetative growth to flowering is a major developmental switch in the plant cycle and the timing of flowering is very critical for reproduction of plant species. In transition to flowering in plants, Flowering locus C (FLC) is one of the crucial factors. Here, we showed How the stability and activity of FLC are regulated by sumoylation mechanism. By pull-down assay, we showed that FLC interact with E3 SUMO ligase in vitro and vivo. And we showed that FLC is sumoylated in vitro condition with AtSUMO1 protein. In transgenic plants with overexpression of FLC and inducible expression of AtSIZ1, sumo E3 ligase led to increase of FLC protein level and delayed the post-translation degradation of FLC indicating that Arabidopsis E3 sumo ligase AtSIZ1 stabilizes FLC. Also, the plants with overexpression of mutant FLC (K154R, a mutation of the sumoylation site on FLC) flowered considerably earlier than plants with overexpression of FLC but comparable with wild type indicating that sumoylation is a important part for function of FLC. Our data indicate that the sumoylation of FLC is critical for its role in the control of flowering time.

Flowering time is a important agronomic trait for grain production in rice. So the control of flowering time is a critical step. In Arabidopsis, expression of certain key flowering gene such as FLOWERING LOCUS C (FLC) is known to be epigenetically regulated by chromatin modification through Enhancer of Zeste[E(z)], a histone methyltransferase, that core component of repressive complex, polycomb repressive complex2(PRC2). However, the chromatin mechanism involved in the regulation of rice flowering genes is presently not well known. Here we show that predict coding region of a intronic LncRNA[termed rice COLDAIR(OsCOLDAIR)], which is expected to associate with a component of PRC2, is predicted at rice FLC gene. And additionally we suggest interaction of histone methyltransferase and E3 SUMO ligase that indicate possibility of interaction with rice E(z) gene and rice E3 SUMO ligase. Our study contribute to control of rice flowering time by observing two factor that can regulate expression of related of rice FLC gene.

Arabidopsis E3 SUMO ligase controls vegetative growth and development including responses to nutrient deficiency and environment stresses. Here, we analyzed seed proteins of its mutant siz1-2. Proteomic analysis showed that the amount of three major nutrient reservoir proteins were decreased in siz1-2 mutants. However, quantitative real-time RT-PCR showed that their transcript levels were significantly high in siz1-2 mutants compared to wild-type plants, which means that these proteins are stabilized by E3 SUMO ligase. In addition, yeast two hybrid assay showed that they interact with E3 SUMO ligase, suggesting that they must be sumoylated by E3 SUMO ligase. Furthermore, tthe analysis of amino acid composition by HPLC showed that the contents of amino acids were a bit high in siz1-2 mutants. Our data indicate that AtSIZ1 plays an important function for accumulation of seed storage proteins through its ligase activity