Identification of genes controlling the action of 9-lox oxylipins in plant defense

• Autores: Satish Kulasekaran
• Directores de la Tesis: Carmen Castresana Fernández (dir. tes.), Crisanto Gutiérrez Armenta (tut. tes.)
• Lectura: En la Universidad Autónoma de Madrid ( España ) en 2012
• Idioma: español
• Tribunal Calificador de la Tesis: Antonio Leyva Tejada (presid.), Marta Martín Basanta (secret.), María del Mar Castellano Moreno (voc.), Antonio Molina Fernández (voc.), Luis Carlos Romero González (voc.)
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• Resumen

  • Oxylipins are a class of lipid metabolites which play an important role in plant development and defense responses against pathogen attack. Principally they are synthesized by the oxygenation of fatty acid molecules through the action of enzymes like 9- and 13-lipoxygenases and ¿-dioxygenases or by chemical oxygenation. The 9-lox oxylipin pathway is a nascent field of research and its role in the defense against pathogenic bacteria has been recently demonstrated. In this study, we carry out a genetic analysis to identify the signaling components of the 9-lox pathway and to annotate its importance in plant defense responses. Through a forward genetic screen, three mutants, namely noxy3, noxy72 and noxy76, from a population of randomly mutagenized arabidopsis thaliana lines were identified to be insensitive to treatment with the 9-lipoxygense derivative, 9-hydroxy octadecatrienoic acid (9-hot). Characterization of responses of these noxy mutants to the hemibiotrophs, pseudomonas syringae has enabled us to identify two negative regulators of plant defense in noxy3 and noxy72, as the mutations in these genes led to enhanced resistance in the stomata and apoplast, respectively. Contrarily, noxy76 mutant exhibited susceptibility to pseudomonas, with a stronger defect in the pre-invasive defense. Mapping of these mutations have revealed that noxy3 and noxy72 encode mitochondrial proteins, namely lon1 protease and a s-adenosyl methionine dependent methyl transferase, respectively. In addition to this, noxy76 was mapped to a heat repeat protein called ilityhia. Further characterization revealed that noxy76 was impaired in stomatal closure in response to bacteria and reactive electrophilic species-oxylipins, whereas this defect was independent of aba. Moreover, characterization of responses to ros and no revealed that noxy76 was impaired in signaling singlet oxygen and no and that it was deficient in the production of no in the stomata. These results when taken together indicated that the defect of noxy76 in producing and signaling no resulted in the failure of activating defense against bacteria.