ROLE OF A POLYAMINE OXIDASE GENE IN THE DEFENSE OF LOTUS JAPONICUS AGAINST PSEUDOMONAS SYRINGAE

BORDENAVE C.; BABUIN M.F.; CAMPESTRE M.P.; ROCCO R.; CALZADILLA P.; MENÉNDEZ A.B.; MAIALE S.J.; RUIZ O.A.; GARRIZ A.

BUENOS AIRES

Simposio; INTERNATIONAL SYMPOSIUM OF FORAGE BREEDING; 2015

COMISIÓN AD HOC PARA SIFB 2015

Polyamines are organic polycations thathave proven to be essential for normal growth anddevelopment in all living organisms. In plants, changes in the metabolism ofthese compounds have been described to occur in response to both pathogenic andbeneficial microbes. In this trend, several lines of evidences suggest that theoccurrence of these changes determines the outcome of the interactions between plantsand microbes. In a previous work, we analyzed global gene expression in twoecotypes of the model legume Lotusjaponicus during the infections caused by the phytopathogenic bacteria Pseudomonas syringae DC3000 pv. tomato. Theseecotypes differ in their tolerances to the bacteria, and accordingly they alsoshow overlapping but distinct gene regulation profiles. Among all the transcriptswhose expression was most significantly modulated, we identified a gene codingfor a putative polyamine oxidase, one of the key enzymes involved in polyaminecatabolism. This enzyme oxidizes higher polyamines as spermidine and sperminewith the production of H2O2, and it is believed toparticipate in the induction of several defense mechanisms during plantpathogen interactions. In this work, we assessed the phenotype of a mutant lineof L. japonicus with a LORE-1insertion in the polyamine oxidase gene locus. Our data show that the absenceof this enzyme remarkably increases the tolerance of the plant, reducingbacteria multiplication as well as the generation of necrosis in infiltratedtissues. This is accompanied by a notably reduction in the production ofradical oxygen species and mild effects on the photosynthetic rate at theinfection site. The importance of polyamine oxidation for plant defenseand the similarities with previously published reports are discussed.