Phosphate-deprivation and damage signalling by extracellular ATP.

Phosphate deprivation compromises plant productivity and modulates immunity. DAMP signalling by extracellular ATP (eATP) could be compromised under phosphate deprivation by the lowered production of cytosolic ATP and the need to salvage eATP as a nutritional phosphate source. Phosphate-starved roots of can still sense eATP, indicating robustness in receptor function. However, the resultant cytosolic free Ca signature is impaired, indicating modulation of downstream components. This perspective on DAMP signalling by extracellular ATP (eATP) addresses the salvage of eATP under phosphate deprivation and its promotion of immunity, how Ca signals are generated and how the Ca signalling pathway could be overcome to allow beneficial fungal root colonization to fulfill phosphate demands. Safe passage for an endophytic fungus allowing root colonization could be achieved by its down-regulation of the Ca channels that act downstream of the eATP receptors and by also preventing ROS accumulation, thus further impairing DAMP signalling.