Heme oxygenase up-regulation under salt stress protects nitrogen metabolism in nodules of soybean plants

The behaviour of enzymes involved in nitrogen metabolism, as well as oxidative stress generation and heme oxygenase gene and protein expression and activity, were analysed in soybean (Glycine max L.) nodules exposed to 50, 100 and 200 mM NaCl concentrations. A significant increase in lipid peroxidation was found with 100 and 200 mM salt treatments. Moreover, superoxide dismutase, catalase and peroxidase activities were decreased under 100 and 200 mM salt. Nitrogenase activity and leghemeoglobin content were diminished and ammonium content increased only under 200 mM NaCl. At 100 mM NaCl, glutamine synthetase (GS) and NADH-glutamate dehydrogenase (GDH) activities were similar to controls, whereas a significant increase (64%) in NADH-glutamate synthase (GOGAT) activity was observed. GS activity did not change at 200 mM salt treatment, but GOGAT and GDH significantly decreased (40 and 50%, respectively). When gene and protein expression of GS and GOGAT were analysed, it was found that they were positively correlated with enzyme activities. In addition, heme oxygenase (HO) activity, protein synthesis and gene expression were significantly increased under 100 mM salt treatment. Our data demonstrated that the up-regulation of HO, as part of antioxidant defence system, could be protecting the soybean nodule nitrogen fixation and assimilation under saline stress conditions. © 2008 Elsevier B.V. All rights reserved.

Fil: Zilli, Carla Giannina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; Argentina

Fil: Balestrasse, Karina Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; Argentina

Fil: Yannarelli, Gustavo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; Argentina

Fil: Polizio, Ariel Héctor. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; Argentina

Fil: Santa Cruz, Diego Mario. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; Argentina

Fil: Tomaro, Maria Lujan. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; Argentina