Evolution of Flower Development: from Phenotypes to Genes
Kramer, Elena M .
The genetic basis for floral novelty in Aquilegia and the Ranunculaceae.
Across the angiosperms there are many examples of independently derived, novel floral organs. The presence of such structures results in five or more distinct floral organ identities, which is difficult to reconcile with the canonical ABC model. In the emerging model system Aquilegia there are five differentiated floral organ types: petaloid sepals, spurred petals, stamens, staminodia and carpels. This morphology would seem to require modifications of the ABC model, namely the capacity to specify two types of petaloid organs as well as a fifth organ identity. Detailed expression studies of the three APETALA3 (AP3) paralogs and one PISTILLATA (PI) homolog in Aquilegia demonstrate that each organ type expresses a specific combination of genes. Furthermore, VIGS-mediated knock-down of B homolog function has found that these loci are essential to staminodium, stamen and petal identity, but play only subtle developmental roles in the petaloid sepals. Our findings show that pre-existing floral organ identity programs can be partitioned and modified to produce additional organ types. They also prove for the first time that some types of petaloid organs are not dependent on AP3/PI homologs for their identity. As an extension of this work, we are examining AP3 and PI expression patterns across the diverse family Ranunculaceae. This study has uncovered evidence of a commonly inherited petal identity program, which is in contrast to the traditional interpretation of Ranunculaceae petals as genuinely homoplasious structures.
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1 - Harvard Univerisity, Organismic and Evolutionary Biology, 16 Divinity Ave, Biolabs 1109, Cambridge, Massachusetts, 02138, USA
MADs box genes
Presentation Type: Symposium or Colloquium Presentation
Location: Stevens 4/Hilton
Date: Wednesday, July 11th, 2007
Time: 2:30 PM