The Impact of Gene Duplication and Divergence on the Formation of Protein Complexes

Abstract

The process of organ identity is relatively well understood in Arabidopsis, where the ABC model explains the genetic basis of floral organ identity. The ABC model contains A, B, and C genes, which are expressed in overlapping fields to produce the four floral organs: sepals, petals, stamens, and carpels. These genes are members of the MADS-box transcription factor family, which function together in protein complexes; however, it remains unknown how evolutionary conserved these MADS-box genes are amongst disparate plant species. To address this, we are interested in studying the process of floral organ identity determination in the lower eudicot Aquilegia (Columbine). This new model system is unique in possessing five types of floral organs. Using virus-induced gene silencing (VIGS) in Aquilegia, we have shown that some duplicated MADS-box genes inherited portions of the ancestral functions while others have evolved entirely new functions related to the fifth type of floral organ. Understanding the process of flower development in Aquilegia offers an important reference point for evolutionary comparisons between different species of flowering plants. Yeast two-hybrid screening was conducted to determine interactions occurring between different Aquilegia MADS-box proteins. The data suggest that the protein produced by the A gene homolog AqFL1 has a much more limited number of interacting partners, which may be consistent with its distinct function in inflorescence structure and leaf development. Interactions of other homologues will also be discussed. Yeast three-hybrid screening is currently being conducted to further understand the process of organ identity in Aquilegia.