Modulation of Putrescine Metabolism in Arabidopsis thaliana by Salicylic Acid

ROSSI FRANCO R; MARÍA MARINA; PIECKENSTAIN FERNANDO L

Rosario

Congreso; 50 Reunion anual de la sociedad argentina de investigaciones en bioquimica y biologia molecular; 2014

Salicylic acid (SA) is a key hormone for defense responses in plants, and plays a critical role in resistance to pathogens. Increments of SA levels activate different signaling cascades in which H2O2 acts as a secondary messenger and in turn activates a large number of mechanisms that contribute to overall plant defense. Polyamines are a group of compounds with multiple physiological roles, which also participate in defense mechanisms against pathogens. The metabolism of the diamine putrescine (Put) is altered by stressful conditions in plants, which generally result in increased Put levels. Previous results showed that exogenous addition of SA induces a high increase in Put levels. In this work, we give evidence that this increase in Put level is mediated by an increase in arginine decarboxylase 2 (ADC2) activity. Moreover, apoplastic Put levels were increased and amine oxidase activity was decreased in plants treated with exogenous SA. Diaminebenzidine (DAB) staining of adc2 mutants (with contain lower Put levels than WT plants), showed that these plants accumulate higher H2O2 levels than WT plants after SA addition. Put supplementation to adc2 mutant plants decreased the H2O2 levels. These results indicate that the accumulation of Put, after the exogenous addition of SA, probably contributes to regulate H2O2 levels during plant defense responses.