La production de la spirale des organes aériens des plantes a lieu dans un tissu spécialisé à l’extrémité de la tige vu ici en microscopie confocale à un stade où la plante produit des fleurs. La décision de produire un nouvel organe comporte une part d’aléatoire, comme si la plante tirait aux dés pour cette décision. Un modèle utilisant cette propriété permet d’expliquer comment les spirales sont produites et de montrer que les irrégularités du processus informent sur les mécanismes menant à la décision de produire un nouvel organe. Copyright : Yassin Refahi, Géraldine Brunoud, Teva Vernoux, Christophe Godin
Exploration of developmental mechanisms classically relies on analysis of pattern regularities. Whether disorders induced by biological noise may carry information on building principles of developmental systems is an important debated question. Here, we addressed theoretically this question using phyllotaxis, the geometric arrangement of plant aerial organs, as a model system. Phyllotaxis arises from reiterative organogenesis driven by lateral inhibitions at the shoot apex. Motivated by recurrent observations of disorders in phyllotaxis patterns, we revisited in depth the classical deterministic view of phyllotaxis.
We developed a stochastic model of primordia initiation at the shoot apex, integrating locality and stochasticity in the patterning system. This stochastic model recapitulates phyllotactic patterns, both regular and irregular, and makes quantitative predictions on the nature of disorders arising from noise. We further show that disorders in phyllotaxis instruct us on the parameters governing phyllotaxis dynamics, thus that disorders can reveal biological watermarks of developmental systems.
The research team was composed of biologists and mathematicians, under the supervision of Teva Vernoux, (RDP) of the l’ENS de Lyon and Christophe Godin of Virtual Plants of INRIA Montpellier.

References: A stochastic multicellular model identifies biological watermarks from disorders in self-organized patterns of phyllotaxis, Yassin Refahi, Geraldine Brunoud, Etienne Farcot, Alain Jean-Marie, Minna Pulkkinen, Teva Vernoux, Christophe Godin, e-life, July, 6th 2016