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The evolutionary mechanism of a flower master regulator revealed


​​​​​​​​Present in algae before plants conquered dry land, the LEAFY protein plays today an essential role in the beauty of the plant world: it governs the formation of flowers. We [1] managed to trace its history and to elucidate the evolutionary mechanism that allowed LEAFY to orchestrate floral morphogenesis. This mechanism has been revealed through the discovery of an ancient intermediate form of the protein that has lasted until today in a moss-related species.

Published on 16 January 2014
[1] International collaboration between a CEA, CNRS and UJF team.
These results are published in Science 16 January 2014.​

The anatomy of a living organism, whether plant or animal, is written in its genome and read by the architects genes that govern the nature and position of its organs. The evolution of living beings over time is often dictated by the evolution of such genes. Mutations of these genes contribute to changing morphologies or create new species. But they can also be fatal if the changes they induce are too brutal. For this reason, the evolution of an architect gene occurs most often after its duplication, an event in which one of the two copies ensures the original function, while the other can freely evolve.

 Researchers have recently shown that the architect gene LEAFY (encoding the eponymous protein) was able to evolve without duplication. In flowering plants, this gene orchestrates the formation of flower buds and its various organs (sepals, petals, stamens and pistil). It was already present, but with different properties, in plants several hundred million years before the appearance of flowers. Evidenced by the presence of LEAFY protein in algae and mosses that are plants without flowers. The acquisition of properties required for its floral function went smooth via an intermediate form that combined old and new features, those of algae and flowering plants. This intermediate form has been identified because it still exists in Nothoceros aenigmatica, a moss-related species. This is the first time that such an evolutionary mechanism is revealed for an architect gene.

This mode of evolution is probably involved in other types of architects genes such as those responsible for the development of embryos in insect or mammalian genes.
Evolution of LFY DNA binding mode (algae in blue, moss in green and flowering plants in orange/red).

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