Caracterización del desarrollo, el estado redox y la respuesta a estrés abiótico y biótico de la línea silenciante-adc de Arabidopsis

Abstract

"Generation of polyamine (PAs) auxotrophic plants has not been achieved since these have been found to be lethal. In our group, an Arabidopsis thaliana line was generated that simultaneously silences the two paralog arginine decarboxylase (AtADC1 and 2) genes through a microRNA, which reduces PAs levels. The aim of this thesis was to study the implications of the deficiency of PAs in the adc-silenced line on the development and response to abiotic and biotic stress in Arabidopsis. In this sense, we observed that the adc-silencing line showed an increase in reactive oxygen species (ROS), as a result of increase in NADPH oxidase activity, as well as a decrease in catalase activity. Also, we found that adc-silenced seedlings had a greater sensitivity to salt and cold stress, evidenced by the decrease in their growth and development, as well as the appearance of chlorosis in leaves. In addition, it was possible to associate the decrease in PAs levels to defects in the processes of cell division and elongation in the Arabidopsis root. Finally, the response of the adc-silenced line to attack by phytopathogenic microorganisms was characterized. Our results show that the adc-silenced line was susceptible to infection by the fungus Botrytis cinerea, and resistant to infection by the bacterium Pseudomonas syringae. Pre-treatments with putrescine (Put) or methyl jasmonate (MeJA) during the interaction with the fungus, and Put pre-treatment for the bacteria were able to restore or increase the expression of defense genes in the adc-silenced line, and in the case of the fungus also prevented the development of symptoms. These findings have provided significant information about the role that PAs plays in the regulation and homeostasis of ROS content, and its effect on root development, as well as the defense response to abiotic and biotic stresses in Arabidopsis thaliana."

"Generation of polyamine (PAs) auxotrophic plants has not been achieved since these have been found to be lethal. In our group, an Arabidopsis thaliana line was generated that simultaneously silences the two paralog arginine decarboxylase (AtADC1 and 2) genes through a microRNA, which reduces PAs levels. The aim of this thesis was to study the implications of the deficiency of PAs in the adc-silenced line on the development and response to abiotic and biotic stress in Arabidopsis. In this sense, we observed that the adc-silencing line showed an increase in reactive oxygen species (ROS), as a result of increase in NADPH oxidase activity, as well as a decrease in catalase activity. Also, we found that adc-silenced seedlings had a greater sensitivity to salt and cold stress, evidenced by the decrease in their growth and development, as well as the appearance of chlorosis in leaves. In addition, it was possible to associate the decrease in PAs levels to defects in the processes of cell division and elongation in the Arabidopsis root. Finally, the response of the adc- silenced line to attack by phytopathogenic microorganisms was characterized. Our results show that the adc-silenced line was susceptible to infection by the fungus Botrytis cinerea, and resistant to infection by the bacterium Pseudomonas syringae. Pre-treatments with putrescine (Put) or methyl jasmonate (MeJA) during the interaction with the fungus, and Put pre-treatment for the bacteria were able to restore or increase the expression of defense genes in the adc-silenced line, and in the case of the fungus also prevented the development of symptoms. These findings have provided significant information about the role that PAs plays in the regulation and homeostasis of ROS content, and its effect on root development, as well as the defense response to abiotic and biotic stresses in Arabidopsis thaliana."