Tracing MADS-Box Gene Function and Regulatory Network Evolution Through Whole Genome Duplication (WGD) In Flowering Plants

We constructed detailed phylogenies of subfamilies of MADS-box transcription factors which show duplications or triplications before the divergence of Gunnerales but after the divergence of Buxales and Trochodendrales. Large-scale phylogenetic and K_S-based approaches on inflorescence transcriptomes confirm the placement of the whole genome event “gamma” in the stem lineage of the core eudicots, comprising 75% of flowering plants. Such a correlation between whole genome duplication and rapid species diversification has been previously observed also for other ancient WGD, but the mechanism is unclear.  Although it is possible that the gamma event triggered early core eudicot diversification, our dating estimates suggest that core eudicot species diversification only occurred several million years later. The evolutionary significance of this paleopolyploidy event may thus rather lie in establishing a species lineage with a genomic potential for later diversification. We are investigating whether and when this potential for species diversification is realized through the functional diversification of regulatory genes, which are preferentially retained after WGD. We study the case of MADS-box genes experimentally to evaluate the functional impact of the gamma triplication on the regulatory network of these key regulators of reproductive development.