Transcriptional regulation under low oxygen stress in plants

Adaptations to low oxygen envision common strategies aimed at either optimizing energy production and consumption, or limiting the extent of oxidative stress and reducing the exposure to low oxygen. Coordination of gene expression is essential to achieve the broad transcriptional reconfiguration that takes place in all organism subjected to oxygen limitations. Recent discoveries have highlighted that, in Arabidopsis, transcriptional adjustments to oxygen depletion are triggered by the ethylene response factor (ERF) RAP2.12 that, being subjected to an oxygendependent proteolytic mechanism, can act like a bridge directly linking oxygen sensing and regulation of low oxygen-responsive genes. This low oxygen sensing system bears some resemblance with the well-known HIF pathway operating in metazoans, which similarly involves the post-translational stabilization of a master activator of hypoxic gene expression. RAP2.12 is constitutively accumulated in the cell and quickly relocated into the nucleus upon hypoxia to promote early transcriptional responses. Several additional hypoxia-inducible transcription factors have been identified in plants, which are supposed to regulate downstream responses: although their functions remain largely undetermined, some of them have been associated to plant adaptations and survival to submergence, flooding, hypoxic or anoxic stresses. Information about the interplay among different components of the transcriptional regulatory network is now required to gain deeper understanding of the way in which plants are able to shape transcription in response to changing oxygen availability.