“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.
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.
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.