Final Activity Report Summary - NO AND II IN PEA (Resistance mechanisms in pea to Erysiphe pisi and Uromyces pisi: nitric oxide and induced inaccesibility) This project focuses on understanding the basis of inherent resistance to powdery mildew and rust in legumes, particularly in the pea, towards identification of resistance forms for sustainable productions systems. This includes the study of nitric oxide involvement as molecular signal in defence mechanisms and also the understanding of induced inaccessibility and accessibility towards identifying totally novel resistance forms. During this first year we adapted and optimised the protocols and techniques to visualise the NO in legumes through confocal microscopy. Furthermore, a new protocol that allows the in vivo observation of NO simultaneously to H2O2 has been established. In addition to the studies we performed in pea, we have also included the model legume Medicago truncatula in our studies. The reason for this is the high amount of molecular information present in data bases that will be extremely useful for our molecular (transcriptomic and proteomic) studies in legumes. We already had Medicago lines with the resistance to rust characterised. However, as far as we know no such identification and characterisation of resistance against powdery mildew has been performed before in M. truncatula. We have assessed macro and microscopically a collection consisting of with 319 accessions provided by USDA. Twelve accessions showed resistance due either to papilla formation, hypersensitive response, or postpenetration mechanisms. Furthermore in the data bases we found 2 ESTs in M. truncatula with high homology to Arabidopsis AtNOS1, the only nitric oxide synthase gene identified in plants. We have partially amplified the cDNA from our plants for future expression studies. Currently we are carrying out the experiments aimed at altering the NO and AOS status in the cells to determine their effect in resistance.
