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A Single Amino Acid Change in the Enhancer of Zeste Ortholog CURLY LEAF Results in

Summary: A Single Amino Acid Change in the Enhancer
of Zeste Ortholog CURLY LEAF Results in
Vernalization-Independent, Rapid Flowering
in Arabidopsis1[C][W][OA]
Mark R. Doyle and Richard M. Amasino*
Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 537061544
Many strains of Arabidopsis (Arabidopsis thaliana) require exposure to prolonged cold for rapid flowering, a process known as
vernalization. Vernalization in Arabidopsis results in the suppression of FLOWERING LOCUS C (FLC), a repressor of
flowering. In a screen for mutants that no longer require vernalization for rapid flowering, we identified a dominant allele of
the Enhancer of Zeste E(z) ortholog CURLY LEAF (CLF), clf-59. CLF is a Polycomb Group gene, and the clf-59 mutant protein
contains a proline-to-serine transition in a cysteine-rich region that precedes the SET domain. Mutant plants are early flowering
and have reduced FLC expression, but, unlike clf loss-of-function mutants, clf-59 mutants do not display additional pleiotropic
phenotypes. clf-59 mutants have elevated levels of trimethylation on lysine 27 of histone H3 (H3K27me3) at FLC. Thus, clf-59
appears to be a gain-of-function allele, and this allele represses FLC without some of the components required for
vernalization-mediated repression. In the course of this work, we also identified a marked difference in H3K27me3 levels at
FLC between plants that contain and those that lack the FRIGIDA (FRI) gene. Furthermore, FRI appears to affect CLF
occupancy at FLC; thus, our work provides insight into the molecular role that FRI plays in delaying the onset of flowering.
The switch from vegetative to reproductive growth
is an important developmental transition in the life
history of flowering plants. The proper timing of this


Source: Amasino, Richard M. - Department of Biochemistry, University of Wisconsin at Madison


Collections: Biology and Medicine