• biosensor
• Marchantia polymorpha
• oxygen sensing
• two component system

The perception of oxygen levels in plants has been widely characterised in angiosperms, while it is still unknown how this mechanism developed during the evolution of land plants. To address this question, we choose the liverwort Marchantia polymorpha. A previous study has identified a set of transcription factors which are induced after hypoxia treatment. We fused each of these transcription factors to a fluorescent protein, cloned the results into expression vectors and transformed Marchantia. We then observed the localization of the reporter via confocal microscopy.
In parallel, we designed a synthetic oxygen sensor in plant. We choose the oxygen-sensing FixL/FixJ two-component system. Firstly, we observed the FixJ subcellular localization. Next, we moved on to assess the signalling potential of the FixJ-FixL couple by cloning the FixJ Responsive Element into a dual-luciferase vector and expressing the system in Arabidopsis protoplasts. We could indeed observe a strong Luciferase activity only in low oxygen condition. Therefore, we stably transformed Arabidopsis plants with FixJ Responsive Element fused with the Firefly Luciferase Gene. Finally, we repeated the Dual-Luciferase Assay on protoplasts of these plants. We identified several lines showing significant Luciferase activity in hypoxia condition.
These results suggest that oxygen-sensing mechanisms from prokaryotes are still functional in plants and can be exploited as oxygen biosensors.