A working model (created with BioRender.com) showing the role of cyclic hypoxia in young leaves. During daytime, photosynthetic activity provides sugars and oxygen, which are the substrates of cellular respiration. This metabolic pathway ensures energy supplies to sustain growth in actively growing young leaves. Oxygen availability also leads to the PCO-dependent oxidation of cysteine (Cox) at the N terminus of ERFVIIs, triggering their degradation via the N-degron pathway during the daytime. However, at night, oxygen provision relies on the gas diffusion, while starch is the main source of sugars for cellular respiration. In these conditions, the high respiration rate leads to a temporary fall (red arrow) in endogenous oxygen levels that triggers ERFVII-dependent hypoxia transcriptional responses. Consequently, ERFVIIs act both as repressors and activators of aerobic and hypoxic metabolism, respectively. This ERFVII-dependent metabolic balance enables the modulation of leaf growth according to the availability of carbon sources and oxygen in actively growing leaves. Arrows and lines indicate promoting and inhibiting effects, respectively.
