Cauliflower, along with dahlias and daisies, develop as phyllotactic spirals. Azpeitia et al. combined modeling with experimental investigation to clarify the gene-regulatory network that sets up a multitude of undeveloped flowers to form a cauliflower curd. Irrepressible inflorescence identity genes in the context of dysfunctional meristems and slow internode elongation result in piles of incomplete flowers. If meristem size drifts during organogenesis, then the conical structures of the Romanesco form emerge in fractal formation.
Science, abg5999, this issue p. 192
Throughout development, plant meristems regularly produce organs in defined spiral, opposite, or whorl patterns. Cauliflowers present an unusual organ arrangement with a multitude of spirals nested over a wide range of scales. How such a fractal, self-similar organization emerges from developmental mechanisms has remained elusive. Combining experimental analyses in an Arabidopsis thaliana cauliflower-like mutant with modeling, we found that curd self-similarity arises because the meristems fail to form flowers but keep the “memory” of their transient passage in a floral state. Additional mutations affecting meristem growth can induce the production of conical structures reminiscent of the conspicuous fractal Romanesco shape. This study reveals how fractal-like forms may emerge from the combination of key, defined perturbations of floral developmental programs and growth dynamics.