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

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2011 p. 83 - 89

0098-8472

The behaviour of enzymes involved in nitrogen metabolism, as well as oxidative stress generation andheme oxygenase gene and protein expression and activity, were analysed in soybean (Glycine max L.) nod-ules exposed to 50, 100 and 200 mM NaCl concentrations. A significant increase in lipid peroxidation wasfound with 100 and 200 mM salt treatments. Moreover, superoxide dismutase, catalase and peroxidaseactivities were decreased under 100 and 200 mM salt. Nitrogenase activity and leghemeoglobin contentwere diminished and ammonium content increased only under 200 mM NaCl. At 100 mM NaCl, glutaminesynthetase (GS) and NADH-glutamate dehydrogenase (GDH) activities were similar to controls, whereas asignificant increase (64%) in NADH-glutamate synthase (GOGAT) activity was observed. GS activity did notchange 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 posi-tively correlated with enzyme activities. In addition, heme oxygenase (HO) activity, protein synthesis andgene expression were significantly increased under 100 mM salt treatment. Our data demonstrated thatthe up-regulation of HO, as part of antioxidant defence system, could be protecting the soybean nodulenitrogen fixation and assimilation under saline stress conditions.