Transcription factors are proteins that bind to DNA to activate or repress gene expression. They have an essential role in animal development. Scientists found out that plants and animals have the most complex repertoire of transcription factors.
A team led by Iñaki Ruiz-Trillo, an evolutionary biologist at the Instituto de Biología Evolutiva (CSIC-UPF), have shown that the growing complexity of transcription factors played an important role in the different unicellular-to-multicellular transitions that took place in life’s history.
This is the result of a work published in the Proceedings of the National Academy of Sciences (PNAS) magazine. Scientists analyzed the repertoire and evolution of transcription factors in a wide variety of eukaryotic genomes (living beings whose cells have a nucleus). Transcription factors are proteins that bind to DNA in order to activate or to repress gene expression, and they play an essential role in animal development.
Among the eukaryotes analyzed there are plants, animals, fungi, and a wide diversity of unicellular organisms, like unicellular algae, amoebas and other types of protists. Scientists found out that plants and animals have the most complex repertoire of transcription factors, both in the number of proteins and in the protein domain architecture of these transcription factors. The authors explain: “The success and the high diversity of animals and plants that we see today can be mostly explained by the acquirement of a high complexity in their transcriptional control”.
A higher complexity in the transcriptional mechanisms implies a higher and finer control of gene expression. “Animals and plants”, say the scientists “have the most complex transcriptional machinery, much more than any other multicellular family, such as multicellular green and brown algae or fungi. This can be due to the fact that both animals and plants have a complex embryonic development which requires a very strict control of gene expression and, therefore, an expanded repertoire of transcription factors.”
Iñaki Ruiz-Trillo explains that this complexity did not appear suddenly but in a step-wide manner: the closest unicellular organisms to both plants and animals (that is, green algae in the case of plants and choanoflagellates and filastereans in the case of animals) already have a significantly complex transcriptional regulation machinery, which was further expanded at the onset of both plants and animal lineages.
Furthermore, scientists analyzed how transcription factors change along the development. “We have seen that transcription factors are significantly expressed mainly during early development in animals and less when animals are adults”. In contrast, transcription factors in plants remain active after the early development, probably because the formation of new structures (branches, leaves, flowers…) still takes place later.
Iñaki Ruiz-Trillo is an ICREA research professor at the Instituto de Biología Evolutiva (CSIC-UPF) and associate professor at the University of Barcelona. The paper is also authored by Alex de Mendoza, Arnau Sebé-Pedrós and Guifré Torruella, the three at the Instituto de Biología Evolutiva (CSIC-UPF) and at the University of Barcelona; Martin Sebastijan Sestakc and Marija Matejcicc, both at the Ruder Boskovic Institute, Croatia; and Tomislav Domazet-Loso, at the Catholic University of Croatia.
More:
Institut de Biología Evolutiva (CSIC-UPF): http://www.ibe.upf-csic.es/people/Permanent_Senior_Researchers/ruiztrillo.html
Transcription factor evolution in eukaryotes and the assembly of the regulatory toolkit in multicellular lineages. Alex de Mendoza, Arnau Sebé-Pedrós, Martin Sebastijan Šestak, Marija Matejčić, Guifré Torruella,Tomislav Domazet-Lošo, and Iñaki Ruiz-Trillo. PNAS 2013 ; published ahead of print November 25, 2013, doi:10.1073/pnas.1311818110