The anatomy of a living organism, whether plant or animal, is inscribed in its genetic make-up: these are the architect 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. Their mutations can thus contribute to evolving morphologies, even creating new organisms. But they can also be fatal, if the changes that they induce are too dramatic. For this reason, the evolution of an architect gene most often occurs after a duplication event, in which one of the two copies ensures the original function, allowing the other to evolve freely.

The researchers have recently shown that the architect gene LEAFY (which encodes the protein of the same name) managed to evolve without duplication. In flowering plants, this gene orchestrates the formation of flower buds and their various organs (sepals, petals, stamens and pistils). It was already present in plants, albeit with different properties, several hundred million years before the appearance of flowers. We see this in the presence of the LEAFY protein in algae and mosses, which do not flower. The acquisition of the properties required for its floral function occurred smoothly, via an intermediate form, which accumulated old and new features (those of algae and flowering plants).

This intermediate form has been identified because it still exists in Nothoceros aenigmatica, a species related to mosses. This is the first time that such an evolutionary mechanism is updated for an architect gene. This mode of evolution is probably involved in other types of architect genes, such as those responsible for the development of embryos in insects or mammals.