Redox-Dependent Condensation of OsSRO1a Links Reactive Oxygen Species Signalling to Panicle Morphogenesis in Rice.

Reactive oxygen species (ROS) are pivotal signalling molecules that coordinate various aspects of plant development. Although ROS has been implicated in controlling stem cell fate within the shoot apical meristem (SAM), its specific role in rice panicle development and grain yield formation remains largely unexplored. Here, OsSRO1a, a plant-specific redox-regulated protein, is identified as a key mediator linking ROS signalling to panicle morphogenesis. Disruption of OsSRO1a leads to severe defects in branching and spikelet formation, alongside abolished responsiveness to ROS perturbation. ROS were found to accumulate in the inflorescence meristem and branch meristem, where they oxidise OsSRO1a at cysteine 387, promoting polymerisation and driving condensation through its intrinsically disordered region IDR3. OsSRO1a condensates recruit the GATA transcription factor NL1 into nuclear foci, enhancing NL1's transcriptional activity and upregulating downstream targets involved in meristem development and redox responses. Together, these results uncover a mechanism whereby ROS-induced condensation of a redox-sensitive protein orchestrates transcriptional reprogramming to shape inflorescence architecture, providing new insights into the integration of redox signalling and developmental regulation in crops.