AUTHOR=Kwak Jun S. , Son Ga H. , Kim Sung-Il , Song Jong T. , Seo Hak S. 

TITLE=Arabidopsis HIGH PLOIDY2 Sumoylates and Stabilizes Flowering Locus C through Its E3 Ligase Activity

JOURNAL=Frontiers in Plant Science

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2016.00530

DOI=10.3389/fpls.2016.00530

ISSN=1664-462X

ABSTRACT=<p>Flowering Locus C (FLC), a floral repressor, plays an important role in flowering. The mechanisms regulating FLC gene expression and protein function have been studied extensively; however, post-translational regulation of FLC remains unclear. Here, we identified <italic>Arabidopsis</italic> HIGH PLOIDY2 (HPY2) as an E3 SUMO ligase for FLC. <italic>In vitro</italic> and <italic>vivo</italic> pull-down assays showed that FLC physically interacts with HPY2. <italic>In vitro</italic> assays showed that the stimulation of FLC sumoylation by HPY2 was dependent on SUMO-activating enzyme E1 and -conjugating enzyme E2, indicating that HPY2 was an E3 SUMO ligase for FLC. In transgenic plants, inducible <italic>HPY2</italic> overexpression increased the concentration of FLC, indicating that HPY2 stabilized FLC through direct sumoylation. Flowering time in <italic>hpy2-2</italic> mutants was shorter than in wild-type plants under long- and short-day conditions, with a greater effect under short-day conditions, and FLC was downregulated in <italic>hpy2-2</italic> mutants. These data indicate that HPY2 regulates FLC function and stability at both the transcriptional and post-translational levels through its E3 SUMO ligase activity.</p>