Auxin export from proximal fruits drives arrest in temporally competent inflorescences

A well-defined set of regulatory pathways control entry into the reproductive phase in flowering plants, but little is known about the mechanistic control of the end-of-flowering despite this being a critical process for optimization of fruit and seed production. Complete fruit removal, or lack of fertile fruit-set, prevents timely inflorescence arrest in Arabidopsis, leading to a previous proposal that a cumulative fruit/seed-derived signal causes simultaneous 'global proliferative arrest'. Recent studies have suggested that inflorescence arrest involves gene expression changes in the inflorescence meristem that are, at least in part, controlled by the FRUITFULL-APETALA2 pathway; however, there is limited understanding of how this process is coordinated at the whole-plant level. Here, we provide a framework for the communication previously inferred in the global proliferative arrest model. We show that the end-of-flowering in Arabidopsis is not 'global' and does not occur synchronously between branches, but rather that the arrest of each inflorescence is a local process, driven by auxin export from fruit proximal to the inflorescence apex. Furthermore, we show that inflorescences are competent for arrest only once they reach a certain developmental age. Understanding the regulation of inflorescence arrest will be of major importance to extending and maximizing crop yields.