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

ZILLI CG; BALESTRASSE KB; YANNARELLI GG; POLIZIO AH; SANTA CRUZ DM; TOMARO ML

ENVIRONMENTAL AND EXPERIMENTAL BOTANY

Elsevier

Año: 2008 vol. 64 p. 83 - 89

0098-8472

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.) nodulesexposed to 50, 100 and 200mMNaCl concentrations. A significant increase in lipid peroxidation was found with 100 and 200mM salt treatments. Moreover, superoxide dismutase, catalase and peroxidase activities were decreased under 100 and 200mM salt. Nitrogenase activity and leghemeoglobin content were diminished and ammonium content increased only under 200mMNaCl. At 100mMNaCl, glutamine synthetase (GS) and NADH-glutamate dehydrogenase (GDH) activitieswere similar to controls, whereas a significant increase (64%) inNADH-glutamate synthase (GOGAT) activitywas observed. GS activity did not change at 200mMsalt 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 100mM 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.