Ozone sensing and early signaling in plants: An outline from the cloud

• High ozone concentrations affect plant metabolism and development.
• Epicuticular waxes, cell wall and plasma membrane are O3-sensing localizations.
• Early O3-signaling components are directly connected to the O3-sensing sites.
• Promising tracks to elucidate putative early O3 signaling components are proposed.

All along their life, plants and trees are exposed to various stresses, and particularly to abiotic ones. Ozone (O3) is one of the most important air pollutants, whose ground levels keep increasing as a result of climate change. High O3 concentrations deeply affect plants and cells, and impact worldwide crop and forest production. In plant leaves, O3 directly interferes with surface tissues or reaches mesophyll cells through stomata. In this case, O3 is almost immediately degraded into reactive oxygen species (ROS) in the apoplastic space of plant cells. For plants to acclimate to O3, the O3 stress signal has to be perceived at the cellular level and relayed to the nucleus to lead to cell reprogramming. The aim of this review is to focus on different O3-sensing localizations, i.e., epicuticular waxes, the cell wall and the plasma membrane, and to detail the different early signaling components related to these sites – in particular lipids, membrane proteins (G proteins, NADPH oxidases and ion channels) and MAP kinases. Finally, some interesting putative membrane-related O3 signaling components are presented as clues to be validated in future investigations.