Evolutionary Developmental Biology (Evo-Devo)
Zhang, Wenheng , Kramer, Elena M , Davis, III, Charles C. .
Floral developmental genetics and the lability of floral symmetry following the loss of a plant-pollinator mutualism.
Floral zygomorphy is an important innovation in flowering plants that is generally thought to have resulted from selection by specialized insect pollinators. We recently demonstrated that homologs of the CYCLOIDEA2-like (CYC2-like) lineage, which are required for establishing floral symmetry in diverse core eudicots, also appear to have been recruited to control zygomorphy in Malpighiaceae. Floral morphology of the neotropical members of this clade is distinctive and highly conserved, especially with regard to symmetry, and is thought to be due to selection by oil-bee pollinators. Two forms of CYC2-like genes in Malpighiaceae, CYC2A and CYC2B, which result from a gene duplication in the common ancestor of the family, show dorsoventral asymmetric expression during late stages of flower development. Here, we characterize genetic basis of floral symmetry in five paleotropical Malpighiaceae clades that have independently lost the specialized oil-bee pollinators and exhibit coincident departures from the stereotyped neotropical floral morphology. Our RT-PCR analyses indicate that changes of CYC2A and CYC2B expression strongly correlate with the alterations of floral symmetry in these species. These results indicate that CYC2 expression is evolutionarily labile in paleotropical clades, which contrasts dramatically with the conserved expression patterns observed in neotropical species. This lability at both the genetic and morphological levels appears to have been produced by a shift in constraints imposed by the insect pollinators.
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1 - Harvard University, Department of Organismic and Evolutionary Biology, 22 Divinity Ave, Cambridge, MA, 02138, USA
2 - Harvard University, Department of Organismic and Evolutionary Biology, 16 Divinity Ave, Cambridge, MA, 02138, USA
Presentation Type: Oral Paper:Papers for Topics
Location: 554A/Convention Center
Date: Monday, August 2nd, 2010
Time: 11:15 AM