Researchers discover a new way for gene-controlling DNA sequences to evolve

Like a person who, before radically changing careers, starts dabbling in an alternative occupation ‘on the side’, genetic sequences called transcription factors can evolve by multitasking, scientists at EMBL Grenoble and colleagues have found. The work, published today in Science, showcases a new way for transcription factors to acquire new roles. Max Nanao, a staff scientist in Andrew McCarthy’s group at EMBL Grenoble, and colleagues in François Parcy’s lab at the Centre National de Recherche Scientifique (CNRS) in France studied a transcription factor called LEAFY. Algae, mosses and land plants have different versions of LEAFY, which control different genes. The scientists found that a group of plants called hornworts have a version of LEAFY that can control all three of those target genes. This multitasking LEAFY provides a stepping-stone on the evolutionary path from an ancient, algal-like LEAFY to the current plant and moss forms.

Video: How different versions of LEAFY evolved. Credit: François Parcy, CEA & Stroma Studios

“Our findings show that gene-control networks can evolve in an unexpected, but intuitive manner,” says Max. The most common – and most studied – way for a transcription factor to evolve new roles is for the cell to first make a copy of that transcription factor. The latter can then mutate and take on new roles without compromising its initial task. By evolving via a multitasking form, LEAFY has made that switch without copying itself – a path that other transcription factors may also have followed, the researchers say.

Further information

Press Release by CNRS (in French)

Source Article

Sayou, C., Monniaux, M., Nanao, M.H., Moyroud, E., Brockington, S.F., Thévenon, E., Chahtane, H., Warthmann, N., Melkonian, M., Zhang, Y., Wong, G.K., Weigel, D., Parcy, F. & Dumas, R. A promiscuous intermediate underlies the evolution of LEAFY DNA binding specificity. Published online in Science Express on 16 January 2014. DOI: 10.1126/science.1248229.

Article Abstract

Transcription factors are key players in evolution. Changes affecting their function can yield novel life forms but also have deleterious effects. Consequently, gene duplication events that release one gene copy from selective pressure are thought to be the common mechanism by which transcription factors acquire new activities. Here we show that LEAFY, a major regulator of flower development and cell division in land plants, underwent changes to its DNA binding specificity, even though plant genomes generally contain a single copy of LEAFY. We examined how these changes occurred at the structural level, and identify an intermediate LEAFY form in hornworts that appears to adopt all different specificities. This promiscuous intermediate could have smoothed the evolutionary transitions thereby allowing LEAFY to evolve new binding specificities while remaining a single copy gene.