Nitric oxide-dependent effects on soybean leaves and isolated chloroplasts

SIMONTACCHI M; GALATRO A; JASID S; INDELICATO S; PUNTARULO S

San Carlos de Bariloche, Argentina

Congreso; XXXIX Annual Meeting Argentine Society for Biochemistry and Molecular Biology, XXXII Annual Meeting Biophysical Society of Argentina, Bariloche Protein Symposium; 2003

Sociedad Argentina de investigación en Bioquímica y Biología Molecular, Sociedad Argentina de Biofísica

Nitric oxide (NO) supplementation in intact soybean (Glycine max var Hood) leaves and isolated chloroplasts was studied. The rate of generation of NO in solution by S-nitrosoglutathione was of 6 microM over the 15 min incubation period. NO incorporation in intact soybean leaves and isolated chloroplasts was assesed by the EPR signal of MGD-Fe-NO adduct. Lipid radical content was no significantly different between control and NO exposed leaves immediately after the treatment. The activity of ascorbate peroxidase (AP) was significantly inhibited (-17%) in intact soybean leaves immediately after exposure to NO (0.72±0.02 and 0.60±0.03 micromol min-1 mg-1 prot, for control and treated leaves, respectively). This effect was completely avoided if the incubation was performed in the presence of hemoglobin. Isolated chloroplasts exposed to GSNO 78, 169, and 255 micromol NO showed a significant decrease of AP activity (48, 53 and 54%, respectively), and a decrease in ascorbyl radical content, despite, the total content of ascorbate was not altered. A 3-fold increase in the generation of H2O2 by chloroplasts exposed to NO, as compared to control chloroplasts, was measured. The data presented here showed that ascorbate metabolism was affected by NO exposure. The effects on chloroplasts suggest that NO could be responsible for an H2O2 increase in the cells.