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Abstract Detail


Developmental and Structural Section

Hernandez-Hernandez, Tania [1], Alvarez-Buylla, Elena [2].

Functional diversification of B MADS-Box homeotic regulators of flower development: adaptive evolution in protein-protein interaction domains after major gene duplication events.

B type MADS-Box genes have been shown to be key regulators during petal and stamen specification in several eudicot model species. Orthologs of these genes have been found across angiosperms and gymnosperms, and it is thought that the basic function of B proteins is conserved in seed plant lineages. The evolution of B genes is characterized by numerous duplications that might be key determinants of their functional diversification, with a determinant impact on floral origins and its morphological evolution. To evaluate the importance of the main duplication events in B MADS-box genes in relation to their functional molecular divergence and consequences in the evolution of the floral developmental program we performed a statistical analysis of molecular evolution of angiosperm B gene sequences. Using maximum likelihood and Bayesian methods we estimated substitution rates and determined the selective regimes operating at each protein residue. Particularly we implemented tests that detect significant differences in substitution rates and sites under positive adaptive selection (PS) in main gene lineages before and after specific duplications. We could identify several protein residues fixed by PS early after the origin of PI-like and AP3-like lineages in angiosperms and early after the origin of the euAP3-like lineage in core eudicots. The residues inferred to have been fixed by positive selection lie mostly within the K domain of the protein, which is key in promoting heterodimerization. These results suggest that novel multimer formation with other MADS proteins could have been fundamental during the functional divergence of B MADS-box genes. We thus propose a mechanism of functional diversification and persistence of gene duplicates by the appearance of novel multimerization capabilities after duplications. Multimer formation in different combinations of regulatory proteins can be a mechanistic base for the origin of novel regulatory functions that can foster the appearance of morphological innovations.


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1 - Instituto de Biologia, Universidad Nacional Autonoma de Mexico, Departamento de Botanica, Circuito exterior s/n, Ciudad Universitaria, Copilco, Coyoacan, A.P. 70-233 Mexico, Distrito Federal. C.P. 04510, Mexico City, DF, C.P. 04510, Mexico
2 - Instituto de Ecologia, Universidad Nacional Autonoma de Mexico, Depto. de Ecologia Funcional, Circuito exterior s/n, Ciudad Universitaria, Copilco, Coyoacan, A.P. 70-233 Mexico, Distrito Federal. C.P. 04510, Mexico City, DF, C.P. 04510, Mexico

Keywords:
B MADS-Box genes
gene functional diversification
developmental evolution
molecular evolution.

Presentation Type: Oral Paper:Papers for Sections
Session: 2-8
Location: 303/Bell Memorial Union
Date: Monday, July 31st, 2006
Time: 10:30 AM
Abstract ID:516


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