Plant Molecular Biology 52: 915–922, 2003.
© 2003 Kluwer Academic Publishers. Printed in the Netherlands.
Genetic interactions between FLM and other ﬂowering-time genes in
, Scott D. Michaels and Richard M. Amasino
Department of Biochemistry of Wisconsin, 433 Babcock Drive, Madison, WI 53706-1544, USA (
author for corres-
pondence; e-mail email@example.com);
Present address: Departamento de Biologia Celular e Genetica,
Universidade Federal do Rio Grande do Norte, Brazil
Received 28 January 2003; accepted in revised form 1 May 2003
Key words: FLM, ﬂowering, MADS-box gene, SVP
FLOWERING LOCUS M (FLM) is a MADS-domain gene that acts as an inhibitor of ﬂowering in Arabidopsis.Here
we describe the genetic interaction of FLM with genes in the photoperiod and autonomous ﬂowering pathways.
Although the sequence of FLM is most similar to that of FLC, FLM and FLC interact with different ﬂowering path-
ways. It has been previously shown that ﬂc lesions suppress the late-ﬂowering phenotype of FRI-containing lines
and autonomous-pathway mutants. However, ﬂm lesions suppress the late-ﬂowering phenotype of photoperiod-
pathway mutants but not that of FRI-containing lines or autonomous-pathway mutants. Another MADS-domain
ﬂowering repressor with a mutant phenotype similar to FLM is SVP. The late-ﬂowering phenotype of FLM over-
expression is suppressed by the svp mutation, and an svp ﬂm double mutant behaves like the single mutants. Thus
FLM and SVP are in the same ﬂowering pathway which interacts with the photoperiod pathway.
Abbreviations: CO, CONSTANS; FLC, FLOWERING LOCUS C; FLM, FLOWERING LOCUS M; FRI, FRIGIDA;
GI, GIGANTEA; LD, LUMINIDEPENDENS; SVP, SHORT VEGETATIVE PHASE; FCA is not an abbreviation
Genetic analysis of the transition to ﬂowering in Ar-
abidopsis has revealed many loci that control this
process (Koornneef et al., 1998a; Simpson et al.,
2002). Mutants that accelerate the transition (early-
ﬂowering mutants) and those that delay it (late-
ﬂowering mutants) have been identiﬁed. The genes
identiﬁed by these mutations have been grouped into
several ﬂowering pathways based upon the affect of
the mutation on the ﬂowering behavior under different
Arabidopsis is a quantitative long-day plant, i.e.,
ﬂowering is promoted by inductive long-day pho-
toperiods, but ﬂowering eventually occurs in non-
inductive photoperiods (Koornneef et al., 1998a).
There are both summer-annual and winter-annual ac-
cessions of Arabidopsis. Summer-annual types rely
primarily on photoperiod as an environmental cue
to initiate ﬂowering. The ﬂowering of winter-annual
types is responsive to photoperiod, but winter annuals
also have a requirement for vernalization (exposure to
a long period of cold such as that of winter) (Michaels
et al., 2000).
The most extensive ﬂowering pathway analyses
have been performed with late-ﬂowering mutants de-
rived from summer-annual types. These mutants are
typically classiﬁed into two major groups (Koorn-
neef et al., 1998a). One group of mutants, consisting
of constans (co), gigantea (gi), fd, fe, fha, ft,and
fwa, deﬁne a photoperiod pathway. Mutants in this
group exhibit a decreased response to photoperiod.
Mutants in the other group, consisting of fca, ﬂower-
ing locus d (ﬂd), fpa, fve, fy,andluminidependens
(ld), deﬁne a pathway referred to as the autonom-
ous or constitutive ﬂoral promotion pathway because