Arabidopsis E3 SUMO ligase SIZ1 (AtSIZ1) controls vegetative growth and development including responses to nutrient deficiency and environment stresses. Here, we analyzed the effect of AtSIZ1 on the stability and amount of seed proteins. Proteomic analysis showed that the amount of three major nutrient reservoir proteins, CRUCIFERIN (CRU) 1, 2 and 3, were decreased in siz1-2 mutants. However, quantitative real-time RT-PCR showed that transcript levels of CRU1, 2 and 3 genes were rather significantly higher in siz1-2 mutants than wild-type plants. Yeast two hybrid analysis revealed that AtSIZ1 interacts with CRU1, CRU2 and CRU3, strongly suggesting that CRU1, 2 and 3 proteins are sumoylated by AtSIZ1. In addition, the 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.

Gene expression is regulated by DNA and histone methylation by DNA and histone methyltransferases, respectively. In animal system, DNA methyltransferase with CG methylation activity is modified by SUMO conjugation and then its activity was increased, which means that the activity of DNA methyltransferase is modulated by posttranslational modification. so Chromatin remodeling is a new concept for expression of controlling of gene function. We thus analyzed the effect of E3 SUMO ligase AtSIZ1 in CMT3 (chromometnylase 3)-mediated genome methylation by next-generation sequencing (NGS), methyl binding domain MeDIP-sequencing and gene analysis using siz1-2 and cmt3 mutants. we carried out CG-enrich analysis by MeDIP sequencing revealed that the methylation level of the genome including transposons was significantly low in siz1-2 mutants compared to wild-type. Result showed the genes regulated by methylation, that genes related of embryo and root development, cellulose metabolism, and post-translational modifications. All of our data indicate that the methyltransfearse activity of CMT3 may be able to be regulated by AtSIZ1 and thereby CMT3-mediated gene expression and plant development also can be controlled by E3 SUMO ligase activity. Besides, our data also suggest that ammonium (NH4+) can stimulate AtSIZ1- and CMT3- mediated DNA methylation.

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.