Oxidative stress and immunolocalization of heme oxygenase in soybean plants.

BALESTRASSE KB; ZILLI CG; SANTA- CRUZ DM; TOMARO ML

Villa Carlos Paz. Argentina.

Congreso; XLIV Reunión Nacional de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2008

We have previously demonstrated that the induction of heme oxygenase-1 (EC 1.14.99.3) plays a protective role for plant cells against oxidative stress. Our research was carried out in leaves and nodules of soybean plants subjected to cadmium and UV-B radiation stresses. Here, we investigated the relationship between salt-induced oxidative stress and heme oxygenase induction in soybean nodules. Treatment with 100 mM  NaCl during 10 days caused a 47% increase in thiobarbituric acid reactive substances, and produced the overexpression of protein and gene heme oxygenase-1, as well as a 2.2-fold enhancement of its activity. Because nodules are the result of a symbiotic association between soybean plants and Bradyrhizobium japonicum bacteria, we determined for the first time the tissular localization of heme oxygenase. Immunohistochemical studies did not allow properly establish the enzyme localization, but electron-microscope examination of immunogold-labeled sections of nodules showed that the inducible isoform of heme oxygenase (HO-1) was only present on the peribacteroid membrane. These results undoubtedly demonstrated that this enzyme is localized in the plant tissue and no in the bacterial symbiont.