LHY and CCA1 play key roles in circadian clock functions and photoperiodic flowering in
Arabidopsis. Double loss of function of
LHY and
CCA1 genes (
lhy cca1) accelerated flowering under long days or short days, but the
lhy cca1 delayed flowering time under constant-light (LL) conditions.
FCA encodes an RNA binding protein that plays key roles in the autonomous pathway. Loss of function of
FCA increases mRNA level of a major floral repressor gene,
FLC. A mutation in
FLC gene partially suppressed the late flowering phenotype of the
lhy cca1 in LL. Based on this result, we have proposed that FLC may be involved in this process. Increased level of
FLC mRNA in
fca is responsible for the delay of flowering and the late flowering phenotype of the
fca is suppressed by vernalization. In this paper, we isolated an enhancer of the late-flowering phenotype of the
lhy cca1 in LL based on natural variation of two
Arabidopsis accessions, Columbia and Landsberg
erecata. The enhancer was named
ELLCL and mapped near the
FLC. This result suggested that the gene responsive to
ELLCL might be
FLC and was consistent with our previous results. The late-flowering phenotype of
lhy cca1 was insensitive to vernalization. By contrast, flowering time of the
fca was accelerated by vernalization as reported. These results suggested that posttranslational, but not the transcriptional, regulation of FLC might be involved in this process.
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