Molecular mechanisms of regulation of ninrate reductase with exogenous 5-aminolevulinic acid in barley seedlings grown under salinization with NaCl
The effect of exogenous 5-aminolevulinic acid (ALA) on the growth and activity of nitrate reductase (NR, EC 1. 6.6.1), the synthesis of proline and the superoxide anion radical generation in barley (Hordeum vulgare L. cv. Gonar) seedlings grown under salinization with NaCl has been studied. The obtained data indicated that ALA (20, 40 and 80 mg L <sup>-1</sup>) increased the elongation and leaf blade expansion of barley seedlings exposed to 150 mM NaCl as compared to control plants, which were not treated with ALA. In the presence of the NR inductor - its substrate 20mM KNO <sub>3</sub>, exogenous ALA stimulated NR gene Nar 1 expression, increased the NR-protein content and enzymatic activities in plants grown in 150 mM NaCl solution. ALA also induced the accumulation of free proline and decreased the generation of superoxide anion radicals. Thus, this study demonstrates that ALA effects on salt-stressed barley seedlings involves the stimulation of NR activities both at transcriptional and translational levels and leads to complex physiological modifications, such as the improvements of plant growth and antiradical defense.