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Developmental and Structural Section

Uimari, Anne [2], Kotilainen, Mika [1], Elomaa, Paula [1], Yu, Deyue [3], Albert, Victor A. [4], Teeri, Teemu H. [1].

Integration of reproductive meristem fates by a SEPALLATA-like MADS box gene: the packaging of seed plant sexuality.

Flowering plants go through several steps between vegetative shoot development and the production of flower parts. Thus far, some of these stages have been studied as distinct fields of inquiry. In Gerbera (Asteraceae), the activity of a single SEPALLATA-like MADS box gene integrates many of these steps. As such, plant scientists may have been overly rash in researching the growth of flowers in isolation from the growth of the flowering shoots that bear them. Unlike the situation inanimals, which display an increase in the complexity of the genetic mechanisms surrounding organ and segment determination (i.e., in the HOX genes, for which there is a trend toward increased cluster number with
organismal complexity in vertebrates), the MADS box genes comprising most of the combinatorial "ABC model" functions underlying flower development, and indeed the extended "ABCDE" model, do not show a profound increase in their
complexity over evolutionary time. In fact, most of the gene duplications that produced the "ABCDE" MADS box gene lineages predate the origin of land plants, and certainly all seed plants in others. What one can observe instead in seed plants is an increase in the degree to which reproductive modules are packed, the angiosperms having the most intricately packed reproductive shoots (flowers). The SEPALLATA-like MADS box genes are known to control a broad variety of developmental modalities having to do with this packaging of reproductive parts: these so-called "E-function floral homeotic genes" participate in the determination of ovule identity, determination of carpel and stamen identity, flower meristem identity, and even inflorescence determinacy (the last three in Gerbera). Following these phenomena in order can also be seen as an evolutionary "degree of packaging" sequence (where ontogeny recapitulates phylogeny), demonstrating that SEPALLATA-like genes are far more generally important (genetically pleiotropic) in reproductive development than previously thought.

1 - University of Helsinki, Department of Applied Biology, P.O. Box 27, Helsinki, FIN-00014, Finland
2 - University of Kuopio, A.I. Virtanen Institute, P.O. Box 1627, Kuopio, 70211, Finland
3 - Nanjing Agricultural University, National Center for Soybean Improvement, Nanjing, 210095, China
4 - University of Oslo, Botanical Garden, Natural History Museums and Botanical Garden, P.O. Box 1172 Blindern, Oslo, NO-0318, Norway

meristem fate
reproductive modules
seed plants
MADS box genes
E function
ABC model
ABCDE model

Presentation Type: Paper
Session: 1-4
Location: Alpine A (Snowbird Center)
Date: Monday, August 2nd, 2004
Time: 8:45 AM
Abstract ID:716

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