OsiEZ1 negatively regulates the expression of floral repressor OsMADS56 by forming complex with long noncoding RNA RIFLA

Abstract

There are many long noncoding RNAs(LncRNAs) in plant. They control various mechanisms. For instance, the lncRNA COLDAIR is one of regulator that is necessary for the repression of a floral repressor FLOWERING LOCUS C (FLC) during vernalization in Arabidopsis thaliana. The repression of FLC is regulated by increased enrichment of Polycomb Repressive Complex 2 (PRC2) and subsequent trimethylation of Histone H3 Lysine 27 (H3K27me3) at FLC chromatin and thereby regulates methylation of target genes and their expression. But, the mechanism how a rice enhancer of zeste rice, OsiEZ1, a homologue of Arabidopsis CLF, methylates target genes and regulates gene silencing is still remained unclear. Here, we show that OsiEZ1 can control expression of rice MADS-box protein gene 56 (OsMADS56), an orthologue of the Arabidopsis floral repressor FLC. LncRNA RIFLA was expressed in the first intron of OsMADS56. lncRNA RIFLA was physically associated with OsiEZ1 and also interacted with histone proteins. Besides, OsiEZ1 interacted with histone proteins and their interaction was enhanced by RIFLA. Moreover, OsiEZ1 strongly interact with rice E3 SUMO ligases OsSIZ1 and OsSIZ2, suggesting that histone OsiEZ1- and lncRNA RIFLA-mediated target gene methylation and expression is controlled by E3 SUMO ligase OsSIZ1 and OsSIZ2. Taken together, our data indicate that OsiEZ1 can regulate expression of OsMADS56 through direct interaction with lncRNA RIFLA and OsiEZ1 activity will be modulated by sumoylation through E3 ligase SUMO activity.