Biocheminal characterization of rice histone methyltransferase OsiEZ1

Abstract

Flowering time is an important agronomic trait for grain production in crop. In Arabidopsis, FLOWERING LOCUS C (FLC) is known as a key controller of flowering time and its expression is epigenetically regulated by chromatin modification through a histone methyltransferase Enhancer of Zeste [E(z)] which is a core component of polycomb repressive complex 2 (PRC2). Long intronic non-coding RNA known as a COLD ASSISTED INTRONIC NONCODING RNA (COLDAIR) is also required for epigenetic repression of FLC expression through its interaction with PRC2. However, the epigenetic regulation mechanism of flowering time is not characterized well in rice. The functional loss of histone methyltransferase OsiEZ1 results in late flowering under short day (SD). Therefore, we investigated the biochemical characteristics of OsiEZ1. Result showed that OsiEZ1 directly interacted a intronic LncRNA expressed in the first intron of OsMADS56, a FLC homolog gene, named OsCOLDAIR. In addition, we found direct interaction between OsiEZ1 and rice E3 SUMO ligase OsSIZ1. These data indicate that OsiEZ1-mediated methylation of OsMADS56 via OsCOLDAIR and that of other target genes can be controlled by sumoylation through E3 SUMO ligase activity of OsiEZ1.