Local regulation of auxin-related pathways in the shoot apical meristem plays a major role during proliferative arrest.

Abstract

The end of flowering is determined by the proliferative arrest process (PA), which takes place after the production of a certain number of flowers and fruits and entails the cessation of all reproductive meristem activity. In this manner, PA guarantees the proper size and viability of offspring before plant death. PA regulation involves a complex interplay of genetic, hormonal, and environmental factors. But still, the molecular mechanisms that govern PA and their spatiotemporal coordination remain poorly understood. Here, we show that the repression of auxin transport and response in the shoot apical meristem (SAM), along with a local reduction of auxin biosynthesis and auxin content, promotes PA. Moreover, our results suggest that auxin and cytokinin pathways must be coordinated in the SAM during PA. Comparative analyses of auxin-related reporters in the SAM of fruitfull (ful) mutants, which fail to undergo PA, and after FUL induction in active meristems, indicate that FUL promotes meristem arrest at least in part by repressing auxin-related pathways. Altogether, our results indicate that local auxin biosynthesis in the SAM, as well as its transport and response, are key in the control of PA.