Activation of the Pro/P5C cycle in Arabidopsis tissues developing the hypersensitive Response

MONTEOLIVA MI; CECCHINI NM; HAJIREZAEI, M-R

Potrero de los Funes, San Luis

Congreso; XLVII Reunión Anual Sociedad Argentina de Bioquímica y Biología Molecular; 2011

Sociedad Argentina de Bioquímica y Biología Molecular

L-proline (Pro) is converted into delta 1-pyrroline-5-carboxylate (P5C) by Pro dehydrogenase (ProDH). P5C is usually transformed into glutamate (Glu) by P5C dehydrogenase (P5CDH). However, under particular conditions, P5C is reduced back to Pro by P5C reductase (P5CR) activating the Pro/P5C cycle together with ProDH. In plants and animals, stimulation of the Pro/P5C cycle is associated with cell death. We suspected that this cycle operates in Arabidopsis tissues generating the Hypersensitive Response (HR) against pathogens. To verify this hypothesis we analyzed ProDH activity (in vivo, in vitro), amino acid content, cell death and reactive oxygen species (ROS) levels in naive and infected tissues. We also tested wild type plants, p5cdh mutants and P5CDH over-expressing plants. Our results confirmed that Pro catabolism is activated in HR before the onset of cell death and that P5CDH and P5CR display different activities along HR progression to activate the Pro/P5C cycle. We speculate that the Pro/P5C cycle potentiates hypersensitive cell death through ROS accumulation.