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Abstract Detail

Evolutionary Developmental Biology (Evo-Devo)

Di Stilio, Veronica [1], Connelly, Caitlin [1].

Evolution of petaloidy and insect pollination in Thalictrum (Ranunculaceae).

THE genus Thalictrum, in the Ranunculaceae, presents a range of flower variation: from inconspicuous, green and wind-pollinated to showy, colorful and insect-pollinated. SEM analysis of perianth epidermis reveals flat cell types in the adaxial epidermis of sepaloid, wind-pollinated T. dioicum compared to conical cells in the perianth of petaloid, insect pollinated T. thalictroides. Trichomes are present in the abaxial epidermis of T. dioicum, along the rim of carpellate sepals and on the surface of carpels. The snapdragon gene MIXTA, a member of the MYB family of transcription factors, plays a role in enhancing petal coloration by affecting epidermal cell shape, rather than pigment concentration, resulting in conical cells that affect light reflection. Three other MIXTA relatives have been identified in snapdragon, involved in different aspects of epidermal cell fate that relate to adaptation to pollinators: conical cells that intensify petal color, trichomes that collect pollen, and mesophyll cell expansion that provides a grasping zone for pollinators. Thalictrum provides an opportunity to explore the role of MIXTA homologs in floral epidermis cell shape, in relation to perianth appearance and pollinator attraction in a basal Eudicot. We have cloned a MIXTA-like homolog from the perianth of Thalictrum thalictroides by PCR, followed by 3 and 5 RACE to obtain the complete cDNA sequence. The Thalictrum predicted protein is sister to snapdragon AmMYBML2 and Petunia PhMYB1, two MIXTA-like proteins with similar functions and ancestral to snapdragon MIXTA, making it the closest relative in this basal Eudicot. We compare the expression pattern of this MYB floral transcription factor in two species of Thalictrum representing distinct floral phenotypes and correlate it to potential upstream regulators, such as a specific member of the B class gene lineage that is differentially expressed in the perianth of the two species studied.

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1 - University of Washington, Department of Biology, Po Box 35-1800, Seattle, Washington, 98195-1800, USA

MYB transcription factor

Presentation Type: Oral Paper:Papers for Topics
Session: 52-8
Location: 303/Bell Memorial Union
Date: Tuesday, August 1st, 2006
Time: 4:15 PM
Abstract ID:703

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