Molecular elements of low-oxygen signaling in plants.

Oxygen and its limitation are emerging as a crucial factor in plant fitness, growth and development. Recent studies revealed the mechanisms by which oxygen is perceived by plant cells. This sensory system partly relies on an oxygen-mediated branch of the N-end rule pathway for protein degradation acting on a specific clade of ethylene responsive transcription factors (ERF-VII). A complementary regulative step is provided by aerobic sequestration of an ERF-VII protein at the plasma membrane and its timely release when hypoxia occurs. Complete absence of oxygen triggers the transient accumulation of reactive hydrogen peroxide and induces an additional set of reactive oxygen species-related genes involved in both signaling and attenuation of oxidative stress. Moreover, temporary hypoxic environments that are built up as consequence of dense cell packing have been demonstrated to trigger cell-fate determination in maize anthers. Similarly, limited oxygen delivery in bulky fruit or tuber tissues growing in aerobic conditions were shown to stimulate anaerobic-like responses. These advances in low-oxygen signaling and its effect on cell development highlight the importance of taking hypoxia into account in agronomical practices as well as in breeding programs.