Identifying candidate genes involved in Nitric Oxide signaling during cell death

Nitric oxide (NO) is an important signaling molecule that mediates many plant developmental and physiological processes. This small gaseous radical was first found to play a crucial role in mediating hypersensitive response induced cell death together with ROS in plant defense reactions against incompatible bacterial pathogens. Beside this it was also shown to influence numerous physiological processes throughout the entire plant life cycle. To study NO responses in plant we have developed a fumigation chamber which allows to treat plants with a precise amount of NO gas concentration in air. Arabidopsis thaliana plants of different ages were first characterized for their response to different NO treatments. In particular we showed that four weeks old Arabidopsis thaliana plants were insensitive to NO fumigation when treated 8 hours with a gas containing up to100 ppm of NO. Using higher NO gas concentrations appearance of typical cell death symptoms was observed. This NO sensitiveness was shown to be strongly dependent on light conditions. In order to identify candidate genes involved in mediating NO signaling during the cell death process we set up a screening strategy taking advantage of this facility. We fumigated a fast neutron mutant collection of Arabidopsis thaliana Columbia plants and are currently fumigating an EMS mutant collection of Arabidopsis thaliana Landsberg erecta plants. Our first screening showed that this setting was successful for the identification of mutants with an altered response to the NO treatment. We could identify 30 mutant plants (0,35%), among which 15 could be successfully propagated and 10 of them were confirmed as more resistant to NO compared to wild type plants in the following generation. Interestingly among them a candidate showing complete NO resistance as well as an altered growth phenotype was identified and is being further characterized