Response of Nitrate Reductase to Exogenous Application of 5-Aminolevulinic Acid in Barley Plants

Information on mechanisms and the pathway for plant nitrogen assimilation by 5-aminolevulinic acid (ALA) is still limited. In addition, the molecular mechanism of nitrate reductase (NR) regulation in response to ALA treatment in plants has not been fully elucidated. In this study, we investigate the effect of different concentrations of exogenous ALA on expression, protein content, and enzyme activity of NR in 7-day-old barley (Hordeum vulgare L.) seedlings grown in the presence of its substrate, KNO3. Our data indicate that the nitrate-inducible Nar1 gene is up-regulated, and protein content and enzyme activity also increase in leaves of barley seedlings treated with ALA. We suggest that one of the mechanisms of ALA-enhanced growth and development of barley plants is regulation of NR at the transcriptional and translational levels.