An oxygen-sensing Polycomb-group protein encodes flooding stress memory in plants

Most organisms, including plants, can encode stress memories that improve resilience to repeated environmental challenges. Flooding events expose plants to recurrent hypoxia, yet whether plants establish an adaptive memory of flooding is unclear. Here we show that somatic flooding stress memory is a conserved feature across multiple angiosperm species. In Arabidopsis, this memory depends on the oxygen-sensitive Polycomb Repressive Complex 2 (PRC2) subunit VERNALIZATION2 (VRN2). Loss of VRN2 impairs epigenetic memory formation and disrupts transcriptional memory at key genes that promote anthocyanin accumulation and repress leaf senescence, adaptive responses that enhance flooding tolerance. Collectively, we reveal a molecular mechanism where VRN2-PRC2 acts as both an oxygen sensor and chromatin effector to establish adaptive flooding stress memory in plants. ShortOur work defines a molecular mechanism for flooding stress memory in plants, actioned via the PRC2 subunit VRN2, that acts as the direct molecular (low) oxygen sensor and transducer. Coupled to its role in cold sensing, this identifies VRN2 as a master sensor subunit of the plant PRC2 that integrates multiple environmental cues to modulate the chromatin landscape and encode environmental memory.