Communicating across generations: the Bsister Language

Bsister proteins form a clade of MADS-box transcription factors that originated 300 million years ago, after ferns diverged but before Angiosperms and Gymnosperms lineages did. Thus, Bsister proteins have been found in both Gymnosperm and Angiosperm species such as paddy oat (Gnetum gnemon), ginkgo, yew (Taxus baccata), rape seed, rice, maize, wheat, petunia, snapdragon, tomato and Arabidopsis. In all these species, they are expressed in female reproductive organs. In this review we go over the evolution and pattern of expression of the Bsister proteins, and we have a glance on their interaction patterns in the form of high order MADS-box complexes in different species. We describe the functions that have been assigned to them according to the analysis of mutants and RNA interference data. We finish this review discussing from a novel point of view the role that Bsister proteins might have, also in tetramer combinations with other MADS-box proteins, on the regulation of tissues communication occurring during reproduction. It is known that a cross-talk is essential for a proper ovule and seed development and Bsister and their target genes might play key roles in these communication processes.