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Abstract Detail

Evolutionary Developmental Biology (Evo-Devo)

Busch, Andrea [1], Zachgo, Sabine [1].

Formation of Corolla Monosymmetry in the Brassicaceae.

An important step in the evolution of angiosperms was the adaptation to specialized pollinators via the establishment of monosymmetric flowers. In the model organism Antirrhinum majus (asterids) monosymmetry is regulated by the activity of the transcription factor CYC (CYCLOIDEA). The typical cruciferous (rosids) flower is comprised of four equally sized petals and only few genera exhibit a monosymmetric corolla. One is the genus Iberis, where monosymmetry is due to two petal pairs of different sizes, the adaxial petals being smaller than the abaxial.
Our motivation was to elucidate if a CYC-homolog is involved in generating monosymmetry in Iberis amara. As a candidate gene IaTCP1 was isolated from I. amara. RT-PCR and in situ hybridization analysis revealed, that IaTCP1 expression correlates with corolla development, being stronger expressed in the small, adaxial petals. Ectopic expression of IaTCP1 in Arabidopsis results in a reduction of petal size. The occurrence of Iberis-flowers with a completely abaxialized corolla together with a corresponding reduction in IaTCP1-transcript abundance confirmed its functional impact in corolla development. CYC/TCP1-like genes have been repeatedly recruited for the establishment of monosymmetric flowers in the two large taxa - the asterids and the rosids. In Iberis, the smaller adaxial petals allow flowers to sit closer together within the inflorescence, which thereby adopts a corymbous shape.
It will be intriguing to determine the effect of inflorescence architecture on pollinator attraction and to speculate on its role as a driving force for speciation in the brassicaceae.

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1 - University of Osnabrueck, Department of Systematic Botany, Barbarastr. 11, Osnabrueck, 49076, Germany

Iberis amara
floral symmetry
TCP transcription factor.

Presentation Type: Oral Paper:Papers for Topics
Session: 53
Location: 101/Law
Date: Wednesday, July 30th, 2008
Time: 10:45 AM
Number: 53009
Abstract ID:737

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