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.