Plant Molecular Biology 46: 515–520, 2001.
© 2001 Kluwer Academic Publishers. Printed in the Netherlands.
Plant development going MADS
Department of Biological Sciences, Gilman Laboratory, Dartmouth College, Hanover, NH 03755, USA (e-mail
Received 10 October 2000; accepted in revised form 6 March 2001
Key words: Arabidopsis, carpel, ﬂower development, ﬂowering time, MADS
It has been known for a decade that the plant MADS genes are important regulators of meristem and ﬂoral organ
identity. The MADS family in Arabidopsis consists of more than 80 members and, until recently, the function of
the majority of these genes was unknown. With the enhanced ability to generate loss-of-function mutants and over-
expression lines, the function of the MADS gene family members is beginning to be elucidated. Recent progress
demonstrates that MADS genes in Arabidopsis are important regulators not only of meristem and ﬂoral organ
identity but also of ﬂowering timing and cell-type speciﬁcation in ﬂoral organs.
Ten years ago the term ‘MADS’ was coined to de-
scribe a family of DNA-binding proteins conserved in
plants, fungi, and animals (Schwarz-Sommer et al.,
1990). The MADS acronym derived from the four
founding members of the MADS family: the yeast
CM1, the plant proteins AGAMOUS and
EFICIENS, and the mammalian protein SERUM
RESPONSE FACTOR. The MADS domain possesses
DNA-binding and dimerization functions and the plant
MADS proteins, like those in yeast and mammals,
function as dimeric transcription factors. The majority
of plant MADS proteins possess a stereotypic domain
structure that consists of the 60 amino acid MADS
domain at the amino-terminal end of the protein and
a second conserved domain, the K domains in the cen-
tral region of the protein (Riechmann and Meyerowitz,
1997) (Figure 1). The 70 amino acid K domain en-
codes a coiled-coil motif that is postulated to mediate
The ﬁrst MADS genes to be characterized in plants
speciﬁed ﬂoral organ identity in Arabidopsis and An-
tirrhinum. The MADS gene family in Arabidopsis,
however, consists of more than 80 members (Ara-
bidopsis Genome Initiative, 2000). It was speculated
Figure 1. Domain structure of plant MADS proteins. Plant MADS
proteins consist of a stereotypic organization of conserved domains.
The MADS domain is located at the amino-terminal end of the pro-
tein and encodes a DNA binding and dimerization function. The K
domain encodes a series of amphipathic α-helices that are postulated
to function as a protein-protein interaction domain, possibly medi-
ating dimerization. The I and C domains are less well conserved.
Recent evidence suggests that the C-domain is necessary for the
formation of higher-order MADS multimers (Egea-Cortines et al.,
1999; Honma and Goto, 2001).
in the early 1990s that the members of the MADS gene
family, in addition to controlling ﬂoral organ develop-
ment, might regulate developmental processes in other
organs and tissues of the plant (Ma et al., 1991). A
series of recent papers indicate that this speculation
was very perceptive.
There are two reasons why it has taken almost a
decade to unravel the function of the MADS genes in
Arabidopsis. First, until recently, there was no way to
easily obtain a loss-of-function mutation in a cloned