Evolution of Flower Development: from Phenotypes to Genes
Di Stilio, Verónica S. , Connelly, Caitlin .
Genetic underpinnings of shifts in pollination-related floral phenotypes in Thalictrum.
Thalictrum, a basal eudicot in the Ranunculaceae, provides an ideal system for studying changes in flower phenotype as they relate to pollination. Flowers are apetalous, and the perianth (sepals) shows adaptation to different pollination vectors. Insect pollinated species have a brightly colored, large perianth or stamens with flattened, petaloid filaments. Wind pollinated species have smaller, inconspicuous green flowers, with sepaloid perianth. Insect pollination is ancestral in the genus, with wind pollination evolving early, and insect pollination secondarily derived in some species. SEM of the adaxial perianth has shown the presence of conical cells in T. thalictroides, a basal insect-pollinated species, and flat cells in T. dioicum, a derived wind-pollinated species. Epidermal cell shape plays an important role in pollination in several species: conical cells attract pollinators by increasing the brightness of petals, and multicellular trichomes increase pollen collection. In snapdragon, MIXTA and related genes are responsible for conical cells and trichomes on the upper epidermis of the petals. We have cloned a MIXTA-related gene from Thalictrum and investigated its expression pattern, asking whether changes in expression of this gene could be responsible for the changes in cell shape in the perianth of these differently pollinated species. The cloned gene, TthMYBML2, is an R2R3 MYB transcription factor phylogenetically most closely related to snapdragon AmMYBML2, a MIXTA-like gene, which induces extended cell growth on the upper epidermis of petals when ectopically expressed in tobacco. Quantitative expression analysis showed increased expression of TthMYBML2 in the perianth of the petaloid insect-pollinated species as compared to the sepaloid wind-pollinated species. We will further discuss the role of this gene in phenotypic differentiation among species of this genus in relation to pollination using a comparative approach.
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1 - University of Washington, Department of Biology, Box 351800, Seattle, WA, 98195-1800, USA
2 - University of Washington, Department of Biology, BOX 351800, Seattle, WA, 98195, USA
myb transcription factor
Presentation Type: Symposium or Colloquium Presentation
Location: Stevens 4/Hilton
Date: Wednesday, July 11th, 2007
Time: 10:30 AM