Cytokinin signalling inhibitory fields provide robustness to phyllotaxis

Fabrice Besnard, Yassin Refahi, Valérie Morin, Benjamin Marteaux, Géraldine Brunoud, Pierre Chambrier, Frédérique Rozier, Vincent Mirabet, Jonathan Legrand, Stéphanie Lainé, Emmanuel Thévenon, Etienne Farcot, Coralie Cellier, Pradeep Das, Anthony Bishopp, Renaud Dumas, François Parcy, Ykä Helariutta, Arezki Boudaoud, Christophe Godin, Jan Traas, Yann Guédon & Teva Vernoux

How biological systems generate reproducible patterns with high precision is a central question in science. The shoot apical meristem (SAM), a specialized tissue producing plant aerial organs, is a developmental system of choice to address this question. Organs are periodically initiated at the SAM at specific spatial positions and this spatiotemporal pattern defines phyllotaxis. Accumulation of the plant hormone auxin triggers organ initiation, whereas auxin depletion around organs generates inhibitory fields that are thought to be sufficient to maintain these patterns and their dynamics. Here we show that another type of hormone-based inhibitory fields, generated directly downstream of auxin by intercellular movement of the cytokinin signalling inhibitor ARABIDOPSIS HISTIDINE PHOSPHOTRANSFER PROTEIN 6 (AHP6), is involved in regulating phyllotactic patterns. We demonstrate that AHP6-based fields establish patterns of cytokinin signalling in the meristem that contribute to the robustness of phyllotaxis by imposing a temporal sequence on organ initiation. Our findings indicate that not one but two distinct hormone-based fields may be required for achieving temporal precision during formation of reiterative structures at the SAM, thus indicating an original mechanism for providing robustness to a dynamic developmental system.

Nature 505 (7483), 417-421

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