Transcriptional analysis of Arabidopsis thaliana Col-0 and erfVII mutant upon reoxygenation
Plants respond to reduced oxygen availability (hypoxia) through oxygen-sensing Plant Cysteine Oxidases (PCOs) and their impact on the stability of transcriptional regulators including Group VII Ethylene Response Factors (ERFVIIs). In hypoxia, such as occurs upon submergence, inefficient PCO activity means ERFVIIs are stable and upregulate the expression of genes which enable an adaptive response. Reactive oxygen species (ROS)-mediated damage is linked to both hypoxia and post-submergence reoxygenation. We found that ERFVIIs are important for seedling survival during post-hypoxia reoxygenation and hypothesised that they may be impacted by ROS. We report that both hypoxia/reoxygenation regimes and direct treatment with H2O2 result in ERFVII nuclear stabilisation, however typical hypoxia marker genes are repressed while upregulated genes include those involved in ROS homeostasis and protection from oxidative stress. Using in planta, heterologous and in vitro assays, we reveal that ROS-related ERFVII stabilisation is caused by PCO inactivation. These stabilised transcription factors are retained at hypoxia responsive promoters although they are converted into transcriptional repressors. Our findings suggest that by responding to both O2 and ROS, PCOs coordinate ERFVII stability to regulate timely responses to damaging fluctuations in oxygen availability.