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Abstract

Dra. María C. Romero-Puertas. Tenured Scientist at the Estación Experimental del Zaidín-CSIC, Granada. Spain

Plants continuously interact with microbes, and such interactions have a notorious impact on plant health. While most studies have focussed in bacterial microbes, fungi are of outmost importance in ecosystems and plant physiology. They can be found in all plant tissues, as endophytic mutualists in leaves and roots, but also as devastating pathogens. In fact, most damaging pathogens are fungi, but also the most ancient and widespread mutualistic plant-microbe symbioses are established with mycorrhizal fungi. These and other beneficial fungi can improve plant growth and stress tolerance. Accordingly, plants have evolved mechanisms to restrict pathogenic interactions while promoting mutualistic relationships. The efficiency of these mechanisms relies in the proper and timely recognition of the interacting fungi and the tight regulation of the immune responses triggered to control (promote or contain) fungal colonization. Therefore, although plants are surrounded by diverse microbial communities both above and under the ground and they are surprisingly healthy considering the vast number of potential pathogens in their environs (Dangl, 2013). Nitric oxide (NO) is a free radical that acts as an intra- and inter-cellular signalling molecule involved in the regulation of many cellular functions in different species. In particular, it has been well documented that NO produced after plant recognition of pathogens is part of the signalling cascades that trigger the expression of defence genes, the production of secondary metabolites and finally, HR and SAR (Bellin et al., 2013). NO function in the plant-fungus interaction however is not so clear (Asai and Yoshioka, 2009). We have used the model plants, tomato and Arabidopsis thaliana, wild type and mutants with altered NO levels to unravel the function of NO in the establishment and evolution of the arbuscular mycorrhizal (AM) symbiosis and plant-F. oxysporum interaction.