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Abstract Detail


Developmental and Structural Section

Sridaran, Sankar [1], Stonebloom, Solomon [1], Bartlett, Madelaine [2], Specht, Chelsea [1].

The labellum of Costus (Zingiberales) and the ABC model of floral development.

The ABC model of floral development proposes that three classes of organ identity genes are required for floral patterning: A class gene expression alone specifies sepal identity, A and B genes expressed together specify petal identity, B and C class gene expression confers stamen identity and C gene expression alone specifies the organ identity of the carpel whorl. The expression patterns of all but one of the ABC genes mirror their domains of activity. Although this model has been well established and expanded upon in model organisms such as Arabidopsis thaliana, little is known about how the ABC model of floral development can be applied to non-model system species, especially those with floral morphologies that suggest alterations in organ identity. Members of the monocot family Costaceae possess a derived petaloid floral organ - the labellum in the stamen whorl. The labellum is formed by the fusion of five primordia that develop from the two stamen whorls two from the inner whorl, three from the outer whorl. One single stamen of the inner whorl remains fertile. Co-expression of AGAMOUS (C class), APETALA3 and PISTILLATA (B class) is required to confer stamen identity in Arabidopsis. Presumably this canonical pattern of gene expression has been modified to produce the labellum of Costus. Using phylogenetic analysis to recover putative orthologs of B and C class genes from species throughout the Zingiberales, we present data on the expression pattern of these genes in developing flowers of Costus dubius using epi-illuminescence microscopy linked to in situ hybridization. This is the first in a number of studies aimed at investigating how evolutionarily conserved genes may be adapted and recruited through the course of evolution to generate morphological novelties.


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1 - UC Berkeley, Plant and Microbial Biology, 111 Koshland Hall, Berkeley, California, 94720-3102, USA
2 - University of California, Berkeley, Plant and Microbial Biology, 111 Koshland Hall, Berkeley, CA, 94720-3102, United States

Keywords:
MADs box genes
Costus
Zingiberales
Floral development
floral morphology
developmental evolution.

Presentation Type: Oral Paper:Papers for Sections
Session: CP26
Location: Boulevard C/Hilton
Date: Tuesday, July 10th, 2007
Time: 9:15 AM
Number: CP26006
Abstract ID:1178


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