Explain mechanism of salt tolerance in higher plants.
Answers
Crop performance is severely affected by high salt concentrations in soils. To engineer more salt-tolerant plants it is crucial to unravel the key components of the plant salt tolerance network. Here we review our understanding of the core salt-tolerance mechanisms in plants. Recent studies have shown that stress sensing and signaling components may play important roles in regulating the plant salinity stress response. We also review key Na+ transport and detoxification pathways and the impact of epigenetic chromatin modifications on salinity tolerance. In addition, we discuss the progress that has been made toward engineering salt tolerance in crops, including marker assisted selection and gene stacking techniques. We also identify key open questions that remain to be addressed in the future.
Keywords: Plant salinity tolerance, NaCl, abiotic stress, engineering of salt-tolerant plants, biotechnology
Soil salinization and its impact on plants
Soil salinization is a growing problem for agriculture worldwide. Salt accumulation in arable soils is mainly derived from irrigation water that contains trace amounts of sodium chloride (NaCl) and from seawater . Increased soil salt concentrations decrease the ability of a plant to take up water and, once Na+ and Cl− are taken up in large amounts by roots, both Na+ and Cl− negatively affect growth by impairing metabolic processes and decreasing photosynthetic efficiency . Thus plant salt stress can be subdivided into early-occurring osmotic stress and slowly increasing ionic Na+ stress with additional Cl− stress (reviewed in. Plants enact mechanisms to mitigate osmotic stress by reducing water loss while maximizing water uptake. Furthermore, plants minimize the harmful effects of ionic Na+ stress by exclusion of Na+ from leaf tissues and by compartmentalization of Na+, mainly into vacuoles . Despite these tolerance mechanisms, salt stress decreases crop yields and is leading to continuing loss of arable land. Such losses are compounded by the additional challenge that agriculture needs to provide enough nutrition for a world population that is rapidly expanding (estimated to reach 9.6 billion by the year 2050) and which has a steadily increasing quality of life . In this context, engineering crops to enhance salt-tolerance mechanisms is a promising approach to address these challenges. In this Review, we examine the key mechanisms that mediate plant salt tolerance and give an overview of recent literature on salinity stress sensing and signaling as well as regulation of gene expression as part of the salt stress response in plants. Furthermore, the understanding of the plant Na+ transport network is updated and an evaluation of methods than can help with the engineering of salt- tolerant crops is made.