Sometimes there are questions that remain unanswered. For a long time, scientists wondered why cabbages had such a special shape, in particular Romanesco cabbage, described as “vegetable crystal”. Two researchers from the Auvergne-Rhône-Alpes region have just unraveled the mystery after twelve years of work and recklessness. One, François Parcy, is a biologist, researcher at CNRS, the other Christophe Godin is mathematician, computer scientist, researcher at Inria.
In 2008, the two men, whose work has just been published in the journal Sciences, began to work on a classic plant, thearabidopsis thaliana, “A weed”, which one finds in cities and along the roads and which has the distinction of being a “cousin” of cabbages. “We already knew, thanks to an American study, that with two genetic mutations, the flowers of this plant could turn into small cauliflowers. This plant therefore served as a model for us to understand the whole reasoning behind this mutation, ”summarizes Christophe Godin.
“A war of territories”
The two scientists and their teams were thus able to determine with certainty that Romanesco cabbage and cauliflower are in fact buds destined to become flowers but which never reach their goal. “We must imagine a war of territories”, continues the mathematician. A merciless struggle between two groups of genes. On the one hand, the group of genes that cause buds to turn into flowers. And on the other, the group of genes that work to turn buds into stems.
“In a classic plant, the first group calls for reinforcements to beat the stem genes. It manages to gain the upper hand to invade the entire territory and block the proliferation of stems. But in the particular case of cabbages, we have discovered that this first group does not manage to impose itself on the second. He is weakening. The result is that the stem buds do not transform into flowers and fall back to the state of stems ”, explains Christophe Godin.
“It’s like fireworks. We have the same type of process ”
The latter try to produce flowers and so on. Cabbage is born from this chain reaction which causes a pile of stems on stems without leaves, multiplying almost infinitely. “It’s like fireworks, a sort of final bouquet. We have the same type of process, ”smiles Christophe Godin.
The atypical shape of Romanesco cabbage is explained by the fact that its stems produce buds more and more quickly (while the production rate is constant in cauliflower). This acceleration gives a pyramidal aspect to each of the florets and thus clearly shows the fractal aspect of the structure.
“We have not yet completely solved the riddle of Romanesco cabbage, modestly admits the researcher. But the results show that we are on the right track. »By modifying one of the genes ofarabidopsis thaliana, the scientists were able to obtain small Romanesco cabbages. “They had the right conical shape but they weren’t perfect,” they explain, confident that they will have solved the mystery for good in the next 5-6 years.