Iron role in oxidative metabolism of soybean axes upon growth

The objective of this work was to study Fe cellular distribution and radical generation during the early stages of growth of soybean embryonic axes. Embryonic axes growth significantly increased both ascorbyl radical content, and the ascorbyl radical/ascorbate content ratio in axes incubated for 48 h as compared to 24 h of incubation, suggesting that oxidative stress conditions have been triggered. The total Fe content was increased by 2-fold in axes incubated for 48 h as compared to the content in axes incubated for 24 h. Embryonic axes isolated from seeds incubated for 24 h yielded 5-7 μg ferritin g−1 FW. Subunits analyses of the protein by SDS-polyacrylamide gel electrophoresis indicated that the protein was composed mainly by a 28 kDa protein subunit, confirmed by immunoblotting. Ferritin (Ft) content declined over axes growth and the content of Fe per molecule of Ft was also decreased over the 48 h period. Labile Fe pool (LIP) was significantly increased after 48 h as compared to 24 h of incubation. Ft content in the axes grown in the presence of 500 μM Fe in the incubation medium was not significantly altered as compared to non-supplemented axes, while LIP content in the axes did. Thus, the increase in the cellular LIP in the embryonic axes upon either growth or Fe supplementation could be responsible for triggering pathways leading to the establishment of adequate preventive mechanisms for avoiding cellular damage by free radicals.