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Resolving the green branch of life: Current progress and future challenges

Kim, Sangtae [2], Koh, Jin [2], Theiβen, Günter [3], Soltis, Pamela S. [1], Soltis, Douglas E. [2].

Phylogeny of floral genes and their expression in basal angiosperms.

One of the most important developments in our understanding of floral evolution and floral organ identity has been the formulation of the ABC model. This model was established based o­n studies of floral organ identity genes of Arabidopsis and Antirrhinum, both representing highly derived lineages of eudicots. However, most of the diversity in arrangement and number of floral parts in angiosperms is found among basal angiosperm lineages. To address whether the ABC model can be applied to all angiosperms, we have investigated the expression patterns of ABC genes in Amborella (Amborellaceae), Nuphar (Nymphaeaceae), Illicium (Austrobaileyaceae), and selected Magnoliales using relative quantitative RT-PCR. We compared our results with expression patterns reported previously for eudicots and monocots. The gene expression patterns in basal angiosperms differ from those in eudicots and monocots in the following ways: 1) genes of the SQUA family (A class) were generally expressed in the fourth whorl (carpels) of flowers and in the leaves, but absent in the first and second whorls, 2) genes of the DEF/GLO family (B class) were generally expressed in the first and fourth whorls, in addition to the second and third whorls, 3) genes of the AG family (C class) were expressed in stamens and carpels and also in tepals of Illicium. In summary, the floral genes of basal angiosperms show a broader range of expression across floral whorls compared to eudicots and monocots, suggesting functional specialization of these floral genes in eudicots and monocots. These gene expression patterns are also consistent with morphological intergradations between adjacent floral organs. Phylogenetic analyses of floral MADS-box genes place sequences from basal angiosperms at the base of most major clades in the MADS-box gene tree.

1 - University of Florida, Department of Natural History, Florida Museum of Natural History, P.O. Box 117800, Gainesville, Florida, 32611-7800, USA
2 - University of Florida, Department of Botany, 220 Bartram Hall, P.O. Box 118526, Gainesville, Florida, 32611-8526, USA
3 - Fridrich-Schiller-Universität Jena, Lehrstuhl fűr Genetik, Philosophenweg 12, Jena, D-07743, Germany

MADS box genes
ABC model
quantitative RT-PCR

Presentation Type: Symposium
Session: 56-2
Location: Ballroom 3 (Cliff Lodge)
Date: Wednesday, August 4th, 2004
Time: 2:00 PM
Abstract ID:128

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