Función del óxido nítrico (NO) en la respuesta de la planta al cadmio y a Fusarium oxysporumPosible conexión entre ambas

Laburpena

In this thesis, we made a bioinformatics analysis of articles published over the last ten years on the production and/or function of NO in plant responses to heavy metals, including Cd. This analysis showed that exogenous applications of NO to the plant protect against heavy metals, particularly Cd, and that, in response to exposure to heavy metals, particularly Cd, plants initially produce NO, which can act as a signal molecule. At a later stage, the plant appears to be equipped with mechanisms to control NO levels, thus preventing further symptoms of toxicity. Using both biochemical techniques, involving modifications in NO levels through chemical donors and scavengers, and molecular approaches, involving the use of mutants with altered levels of NO, we subsequently analysed the role of NO in Arabidopsis seedling responses to Cd stress and its relationship to ROS. We also show that prolonged production of NO in plant responses to Cd can indeed affect antioxidant systems and induce oxidative stress, suggesting yet again that NO levels need to be strictly regulated in plant responses to Cd stress in order to prevent further damage to the plant. Peroxisomes have recently been shown to play a key role in a plant's early response to Cd stress. While both NO and RNS have been detected in these organelles, little is known about their effect on peroxisomal metabolism and dynamics. In this thesis, we analysed the role of NO in peroxisomal metabolism, distribution and dynamics under control conditions and in response to Cd stress. We showed that NO is involved in changes observed in peroxisomal dynamics which are necessary for the plant to respond to Cd stress. We also demonstrated the effect of NO on the oxidative metabolism of peroxisomes and their cellular distribution, as well as on organelledependent signalling. In addition, we analysed the little-known role of NO in Arabidopsis-Fusarium oxysporum interactions. We found that NO metabolism mutants have differential fungal responses with respect to WT in terms of ROS production, phenols, secondary and iron metabolisms; as well as defence gene induction Also, nitrate reductase appears to be essential for adequate cell wall assembly through the regulation of CESA4 and MYB46, given that the cell wall is a key barrier in the plant’s defence against Fusarium oxysporum. Finally, pre-treatment with Cd was found to protect plants against Fusarium oxysporum and to increase their survival. This could be explained by a priming effect, as certain genes are common to different plant responses to Cd and fungi, particularly Fusarium, suggesting that crosstalk takes place between both these stress conditions.