Evolutionary Developmental Biology (Evo-Devo)
Zhang, Wenheng , Kramer, Elena M , Davis, III, Charles C. .
Exploring the developmental genetic basis of independent reversals in floral symmetry in Malpighiaceae.
Floral zygomorphy was an important innovation during angiosperm evolution. The CYC2 lineage of the TCP transcription factor family is required for establishing zygomorphy in diverse groups of core eudicots. We have pursued a comparative expression study of CYC2 homologs in a phylogenetic context. Our results indicate that members of this lineage were also recruited for controlling zygomorphy in Malpighiaceae. Most species of Malpighiaceae have two copies of CYC2-like genes, CYC2A and CYC2B, with gene duplication predating the common ancestor of the family. Both CYC2 copies show dorsoventral asymmetric expression during late stages of flower development. Conservation of CYC2A and CYC2B expression appears to have been maintained across a span of 65 million years in the flowers of neotropical Malpighiaceae. Furthermore, we have examined the genetic basis of multiple independent losses or modifications of zygomorphy in paleotropical Malpighiaceae. The neotropical floral morphology of Malpighiaceae, including a distinct dorsal flag petal and oil glands on the sepals, was lost independently several times in the paleotropics, where the oil bee pollinators of the neotropics are absent. In some cases this involves a complete loss of zygomorphy while in others, plane of floral symmetry is shifted. Our goal is to understand how changes in CYC2 function or expression correlate with these alterations in floral symmetry. Evidence from multiple lines suggests that changes in CYC2 expression correlate with these alterations in floral symmetry. We also note an interesting pattern of gene lineage evolution in paleotropical Malpighiaceae. It seems that a higher percentage of paleotropical malpighs have lost either CYC2A or CYC2B (4/9 taxa vs. 21/23 of New World). It remains to be seen how these gene loss events may have influenced floral morphology.
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1 - Harvard University, Department of Organismal and Evoloutionary Biology, 22 Divinity Ave., Cambridge, MA, 02138
2 - Harvard Univerisity, Organismic and Evolutionary Biology, 16 Divinity Ave, Biolabs 1109, Cambridge, Massachusetts, 02138, USA
Presentation Type: Poster:Posters for Topics
Location: Event Tent/Cliff Lodge
Date: Monday, July 27th, 2009
Time: 5:30 PM