The SVP-FRO6 Module Integrates the Control of Leaf Senescence and Flowering in Arabidopsis.

Plants coordinate major developmental transitions by integrating intrinsic genetic programs with environmental signals, where nutrient availability serves as a critical external factor shaping growth and fitness. Iron (Fe), an essential micronutrient for cellular respiration and photosynthesis, is strictly regulated through sophisticated uptake and transport systems, yet its specific role in timing developmental transitions, particularly leaf senescence and flowering, remains largely unresolved. Here, we show that total Fe concentration gradually increases with leaf age and excessive Fe accumulation accelerates leaf senescence in Arabidopsis. We identify Ferric Reduction Oxidase 6 (FRO6), a ferric reductase family protein, as a novel negative regulator of leaf senescence that modulates Fe accumulation in leaves. Our results indicate that FRO6 contributes to the regulation of leaf senescence across a broad range of Fe availability, from deficiency to excess. Furthermore, we find that FRO6 regulates the transcript levels of MYC2, a master regulator of jasmonic acid signalling and environmental stress responses, to modulate leaf senescence. In addition, Short Vegetative Phase (SVP), a key floral repressor, directly activates FRO6 expression by binding to its promoter, thereby establishing an SVP-FRO6 regulatory module that coordinates the timing of leaf senescence and floral transition. Collectively, these results provide new mechanistic insights into how Fe homoeostasis in leaves interfaces with leaf senescence and reproductive development, highlighting Fe as a pivotal regulator of plant developmental timing.