Characterization of HoMADS1 and its induction by plant hormones
during in vitro ovule development in Hyacinthus orientalis L.
Hong Yan Xu
, Xing Guo Li
, Quan Zi Li
, Shu Nong Bai
, Wen Liang Lu
College of Life Sciences, Shandong Agricultural University, Taian, Shandong 271018, China (*author for
correspondence; e-mail firstname.lastname@example.org);
College of Life Sciences, Beijing University, Beijing 100871,
Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China;
Present address: College
of Life Sciences, Yantai Normal University, Yantai, Shandong 264025, China
Received 3 February 2004; accepted in revised form 22 April 2004
Key words: expression pattern, functional analysis, HoMADS1, hormones, in vitro ovule development
To understand the molecular mechanism of ovule development, a MADS box gene, HoMADS1, has been
isolated from the ovule tissues of Hyacinthus. Sequence comparison showed that HoMADS1 is highly
homologous to both class C and D genes. Furthermore, phylogenetic analysis suggests that HoMADS1 is
most likely a class D MADS box gene. RNA hybridization revealed that HoMADS1 was exclusively
expressed in the ovules. Over-expressing HoMADS1 in transgenic Arabidopsis plants produced ectopic
carpelloid structures, including ovules, indicating that HoMADS1 is involved in the determination of carpel
and ovule identities. Interestingly, during in vitro ﬂowering, no HoMADS1 mRNA was detected in the
ﬂoral tissues at high level hormones in the media. However, HoMADS1 mRNA accumulated in the ﬂoral
tissues when the regenerated ﬂowers were transferred to the media containing low level hormones which
could induce in vitro ovule formation. Our data suggest that the induction of HoMADS1 by plant hor-
mones may play important roles during ovule initiation and development in the regenerated ﬂower.
Whether HoMADS1 expression is also regulated by cytokinin and auxin during ovule development in
planta remains to be investigated.
In angiosperms, pistil is the female reproductive
organ that plays a central role in plant sexual
reproduction and agriculture. Pistil commonly
consists of the stigma, the style and the ovary.
During ﬂower development, ovule diﬀerentiation
starts from the placenta in the ovary and ulti-
mately results in the formation of a female game-
tophyte, which contains a haploid egg cell and a
diploid central cell. After fertilization, the ovule
ﬁnally develops into a seed (Gasser and Robinson-
Beers, 1993; Reiser and Fischer, 1993).
Based on the basis of genetic and molecular
analysis, the ABC model was proposed to describe
the action and interactions of three classes of
homeotic gene A, B and C, which determine the
ﬂoral organ identity. Each class of the genes
functioning in two adjacent whorls has been
identiﬁed from many plant species. In Arabidop-
sis, the class A genes including APETALA1 (AP1)
and APETALA2 (AP2) are required for sepal and
petal determination, the class B genes APETALA3
(AP3) and PISTILLATA (PI ) for petal and sta-
men formation, and the class C gene AGAMOUS
(AG) for stamen and carpel speciﬁcation. Se-
quence analysis revealed that the genes AP1, AP3,
PI and AG contain a conserved MADS box, and
therefore they were designated as MADS box
genes (Yanofsky et al., 1990; Coen and Meyero-
Plant Molecular Biology 55: 209–220, 2004.
Ó 2004 Kluwer Academic Publishers. Printed in the Netherlands.