Trends in genetic engineering of plants with (Na+/H+) antiporters for salt stress tolerance

Salinity is one of the major constraints to world agriculture production and the recent phenomenon of global climatic change has further exacerbated the problem. To cope with excess salinity, manipulation of transgenic technology in crop plants has been proven effective in recent years. Among all available strategies, the membrane and vacuolar Na+/H+ antiporters provide the best mechanism for ionic homeostasis in plants under salt stress. In recent years, a large number of transgenic plants with variable salt tolerance have been produced on the basis of antiporter genes. Most of these experiments were conducted under laboratory conditions and at the early plant developmental stages. Only a few studies conducted under field conditions revealed the true potential of antiporter genes in salt tolerance and effects on the overall plant growth and yield. More field trials are required to investigate the already claimed salt tolerance and whether this salt tolerance has any incremental advantage in terms of the ultimate yield potential. In addition, alternative strategies are needed to improve the performance of antiporter genes and the underlying processes by studying the halophyte salt tolerance mechanisms. This review focuses on the present status and progress in the development of salt-tolerant transgenic plants with Na+/H+ antiporter genes. More importantly, the potential future target areas for enhancing salt tolerance with the antiporter genes are discussed.