Over-Expression of a Maize N-Acetylglutamate Kinase Gene (ZmNAGK) Improves Drought Tolerance in Tobacco

Abstract

Water deficit is a key limiting factor that affects the growth, development and productivity of crops. It is vital to understand the mechanisms by which plants respond to drought stress. Here an <i>N</i>-acetylglutamate kinase gene, <i>ZmNAGK</i>, was cloned from maize (<i>Zea mays</i>). <i>ZmNAGK</i> was expressed at high levels in maize leaves and at lower levels in root, stem, female flower and male flower. The expression of <i>ZmNAGK</i> was significantly induced by PEG, NaCl, ABA, brassinosteroid and H₂O₂. The ectopic expression of <i>ZmNAGK</i> in tobacco resulted in higher tolerance to drought compared to plants transformed with empty vector. Further physiological analysis revealed that overexpression of <i>ZmNAGK</i> could enhance the activities of antioxidant defense enzymes, and decrease malondialdehyde content and leakage of electrolyte in tobacco under drought stress. Moreover, the <i>ZmNAGK</i> transgenic tobacco accumulated more arginine and nitric oxide (NO) than control plants under drought stress. In addition, the <i>ZmNAGK</i> transgenic tobaccos activated drought responses faster than vector-transformed plants. These results indicate that <i>ZmNAGK</i> can play a vital role in enhancing drought tolerance by likely affecting the arginine and NO accumulation, and <i>ZmNAGK</i> could be involved in different strategies in response to drought stress.