Sepallata genes and their role during floral organ formation

Charles Darwin called the ability and success of angiosperms to colonise various parts of the earth even under unfavorable conditions an abominable mystery. This mystery is still not solved but one idea to explain the success of angiosperms is the development of the flower. SEPALLATA genes are common across angiosperms and play a major role in the development of all four floral organs and meristem determinacy. SEP genes occurred via Whole Genome Duplication (WGD) and are described as redundantly acting genes in the model organism A. thaliana. However, this study shows non-redundant functions affecting all floral organs for all four genes, especially under elevated growth conditions affecting the robustness and reproductive fitness of the plant, suggesting a diversification. SEPALLATA4 in particularly has a specific role within this gene family based on its early expression pattern compared to the other SEPs and its effect on flowering time, floral meristem maintenance, floral organ identity and organ number. The identification of genome wide targets of SEP4 and expression analysis revealed a bi-functional role for this transcription factor during flower development. Comparison between SEP3 and SEP4 targets revealed a large number of common but also independent targets, indicating that flower development is regulated to a large degree redundantly but also has independent ways of regulation. This suggests that maintenance of multiple genes after a WGD event in angiosperms causes diversification in-between these genes and contributes to the robustness of the plant to environmental perturbations and has influenced their ability to radiate and occupy different ecological niches. This might be one explanation to explain the tremendous success of flowering plants.