Oxygen is a key signalling component of plant biology and, whilst an oxygen-sensing mechanism was previously described in Arabidopsis thaliana. However, key features of the associated PCO N-degron pathway and Group VII ETHYLENE RESPONSE FACTOR (ERFVII) transcription factor substrates remain unknown. We demonstrate that ERFVIIs show non-autonomous activation of root hypoxia tolerance, and are essential for root development and survival under oxygen limiting conditions in the soil. We determine the combined effects of ERFVIIs in controlling genome expression and define genetic and environmental components required for proteasome-dependent oxygen-regulated stability of ERFVIIs through the PCO N-degron pathway. Using a plant extract, unexpected amino-terminal cysteine oxidation to sulphonic acid oxidation level of ERFVIIs was defined, suggesting a requirement for additional enzymatic activity within the pathway. Our results provide a holistic understanding of the properties, functions and readouts of this oxygen-sensing mechanism defined through its role in modulating ERFVII stability.