16
Evolution of Reproductive Organs
in Vascular Plants
MITSUYASU HASEBE 1 AND MOTOMI IT02
I National Institute for Basic Biology, 38 Nishigonaka, Myodaiji-cho, Okazaki 444-8585,
Japan
2 Department of Biology, Faculty of Science, Chiba University, 1-33 Yayoicho, Inage-ku,
Chiba 263-0022, Japan
Abstract
A t10wer is the most complicated reproductive organ of a plant and is composed of
four t10ral organs, namely carpels, stamens, petals and sepals. Development of the
t10ral organs is mainly regulated by the members of the MADS transcription factors, and the evolution of reproductive organs is related to the evolution of the
MADS genes. Based on recent studies of MADS genes in gymnosperms and ferns
it has been speculated that the common ancestor of vascular plants had only a few
MADS genes and the patterns of expression were ubiquitous. (1) The increase of
MADS genes by gene duplication and (2) the recruitment of some MADS genes to
be expressed in specific tissues were likely to have been important for the evolution
of complicated reproductive organs, such as angiosperm t1owers, from simple reproductive organs like fern spqrangia.
1 Evolution of Reproductive Organs
in Vascular Plants
A flower is the most complex reproductive organ in land plants and is usually
composed of a receptacle and four kinds of t10ral organs arranged in four whorls;
sepals, petals, stamens (microsporophylls), and carpels (megasporophylls) as shown
in Fig. 1. Haploid cells corresponding to miero- and megaspores are formed by
meiosis in a stamen and a gynoecium. Microspores are enclosed in a micros poKey words. MADS, LEAFY, homeotic gene, flower development, molecular evolution, flower
evolution, angiosperm, gymnosperm, Gnetum, Ginkgo, conifers, fern, evolutionary development
243
Evolution of Reproductive Organs
in Vascular Plants
MITSUYASU HASEBE 1 AND MOTOMI IT02
I National Institute for Basic Biology, 38 Nishigonaka, Myodaiji-cho, Okazaki 444-8585,
Japan
2 Department of Biology, Faculty of Science, Chiba University, 1-33 Yayoicho, Inage-ku,
Chiba 263-0022, Japan
Abstract
A t10wer is the most complicated reproductive organ of a plant and is composed of
four t10ral organs, namely carpels, stamens, petals and sepals. Development of the
t10ral organs is mainly regulated by the members of the MADS transcription factors, and the evolution of reproductive organs is related to the evolution of the
MADS genes. Based on recent studies of MADS genes in gymnosperms and ferns
it has been speculated that the common ancestor of vascular plants had only a few
MADS genes and the patterns of expression were ubiquitous. (1) The increase of
MADS genes by gene duplication and (2) the recruitment of some MADS genes to
be expressed in specific tissues were likely to have been important for the evolution
of complicated reproductive organs, such as angiosperm t1owers, from simple reproductive organs like fern spqrangia.
1 Evolution of Reproductive Organs
in Vascular Plants
A flower is the most complex reproductive organ in land plants and is usually
composed of a receptacle and four kinds of t10ral organs arranged in four whorls;
sepals, petals, stamens (microsporophylls), and carpels (megasporophylls) as shown
in Fig. 1. Haploid cells corresponding to miero- and megaspores are formed by
meiosis in a stamen and a gynoecium. Microspores are enclosed in a micros poKey words. MADS, LEAFY, homeotic gene, flower development, molecular evolution, flower
evolution, angiosperm, gymnosperm, Gnetum, Ginkgo, conifers, fern, evolutionary development
243