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

Weijuan Liu,Jingwei Yan,Xiujuan Sun,Aying Zhang,Xiaoyun Zhang,Gaoqiang Han,Yang Xiang,Henrik Vibe Scheller,Yu Sheng

doi:10.3389/fpls.2018.01902

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

Highlights

Along with global growing population and climate change, water resource scarcity is one of the great environmental challenges of our time
Multiple sequence alignment showed that NAGK was highly conserved among A. thaliana, Brachypodium distachyon, N. tabacum, Oryza sativa, Setaria italica, Sorghum bicolor, and Z. mays, except for 60 amino acid residues at the N-terminus
We found that the detached leaves of the ZmNAGK transgenic tobaccos lost water at a lower rate (Figure 4B) and had minimal lower stomatal density (Figure 4C)

Summary

Introduction

Along with global growing population and climate change, water resource scarcity is one of the great environmental challenges of our time. Plants encounter many abiotic stresses that affect growth and development, and water deficit is one of the main factors that lead to substantial yield reduction (Boyer, 1982). It is crucial to understand the mechanisms of plant response to drought (Daryanto et al, 2016). A broad range of strategies at physiological and molecular levels have been developed in plants to help them adapt to stress (Mazzucotelli et al, 2008). Abscisic acid (ABA) plays a vital role in modulating the expression of stress-related genes and cellular responses to drought stress (Todaka et al, 2017). Exogenous 24-epiBL (24-epibrassionlide) can improve the drought tolerance by reducing lipid peroxidation, plasma membrane penetration and enhancing

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Discussion

Conclusion