Cross-Regulation of Metabolic and Immune Pathways in Plants Under Hypoxic Conditions

Plants are sessile organisms that use molecular oxygen to perform basic metabolic functions. However, when oxygen availability decreases to 1-5% (hypoxic stress), the plant responds transcriptionally to adjust its metabolism and survive the stress. It has been observed that during hypoxia, adenosine triphosphate (ATP) levels decrease drastically, which could trigger plant death. However, despite experiencing an energy deficit, it has been observed that during hypoxia, plants induce defense mechanisms against pathogens. Plants manage to evade pathogenic microorganisms during an energy deficit by using complex signaling networks and different levels of regulation (transcriptional, post-translational, physiological, metabolomic, etc.) that converge to respond to both types of stress (biotic and abiotic). Understanding this phenomenon would have potential applications for agriculture and crop improvement. Therefore, this review details the main mechanisms of plant response to hypoxia and how this affects immunity mechanisms, highlighting the participation of ERF-VII transcription factors as oxygen sensors and their ability to bind to the GCC-box present in promoter regions of defense genes, MAPK signaling pathways, hormonal pathways, ROS, and Ca²⁺.