Na+ Tolerance and Na+ Transport in Higher Plants

Abstract

Tolerance to high soil [Na(+)] involves processes in many different parts of the plant, and is manifested in a wide range of specializations at disparate levels of organization, such as gross morphology, membrane transport, biochemistry and gene transcription. Multiple adaptations to high [Na(+)] operate concurrently within a particular plant, and mechanisms of tolerance show large taxonomic variation. These mechanisms can occur in all cells within the plant, or can occur in specific cell types, reflecting adaptations at two major levels of organization: those that confer tolerance to individual cells, and those that contribute to tolerance not of cells per se, but of the whole plant. Salt-tolerant cells can contribute to salt tolerance of plants; but we suggest that equally important in a wide range of conditions are processes involving the management of Na(+) movements within the plant. These require specific cell types in specific locations within the plant catalysing transport in a coordinated manner. For further understanding of whole plant tolerance, we require more knowledge of cell-specific transport processes and the consequences of manipulation of transporters and signalling elements in specific cell types.

Cell-Type-Specific H+-ATPase Activity in Root Tissues Enables K+ Retention and Mediates Acclimation of Barley (Hordeum vulgare) to Salinity Stress

“…To date, attempts to create salttolerant crop germplasm have had limited success (Flowers, 2004;Shabala, 2013), largely due to the high physiological and genetic complexity of this trait. It is estimated that salinity affects transcripts of approximately 8% of all genes (Tester and Davenport, 2003), and fewer than 25% of these salt-regulated genes are salt stress specific (Ma et al, 2006). At the physiological level, numerous subtraits contribute to overall salinity tolerance, most of which are species specific and may require expression in either a particular tissue or cell type (Tester and Davenport, 2003;Shabala, 2013).…”

“…It is estimated that salinity affects transcripts of approximately 8% of all genes (Tester and Davenport, 2003), and fewer than 25% of these salt-regulated genes are salt stress specific (Ma et al, 2006). At the physiological level, numerous subtraits contribute to overall salinity tolerance, most of which are species specific and may require expression in either a particular tissue or cell type (Tester and Davenport, 2003;Shabala, 2013). It is thought that the limited success of transgenic manipulations to increase some of these traits (and, specifically, those related to ion exclusion from the shoot) is due largely to the inability to express important exclusion genes in a cell-specific manner .…”

“…Physiologically, plant adaptive responses to salinity can be grouped into four major categories: (1) dealing with the osmotic component of salt stress; (2) handling toxic Na + and Cl 2 ions; (3) detoxifying reactive oxygen species (ROS) produced in plant tissues under saline conditions; and (4) mediating cytosolic K + homeostasis (Tester and Davenport, 2003;Ji et al, 2013;Shabala, 2013;Shabala and Pottosin, 2014;Flowers et al, 2015;Julkowska and Testerink, 2015;Kurusu et al, 2015). All these responses rely heavily on the regulation of transport activity across cellular membranes and, specifically, those for Na + and K + ions.…”

“…All these responses rely heavily on the regulation of transport activity across cellular membranes and, specifically, those for Na + and K + ions. High cytosolic Na + concentrations are considered to be toxic for cell metabolism and, thus, are reduced by various means (Tester and Davenport, 2003;Ji et al, 2013;Flowers et al, 2015). At the same time, superior K + retention and a cell's ability to maintain cytosolic K + homeostasis correlate with salinity tolerance in a broad range of plant species (Anschütz et al, 2014;Shabala and Pottosin, 2014) and are essential for preventing salinityinduced programmed cell death (Shabala, 2009;Demidchik et al, 2010).…”

Overexpression of AtSZF2 from Arabidopsis Showed Enhanced Tolerance to Salt Stress in Soybean

“…However, plants have adapted to environmental challenges by expressing many plant genes in response to the stresses. The cellular and molecular mechanism of plants to abiotic stresses have been studied by many research groups (Shinozaki and Yamaguchi-Shinozaki 2000;Hasegawa et al 2000;Xiong et al 2002;Zhu 2002;Shinozaki et al 2003;Tester and Davenport 2003;Zhu 2003;Sun et al 2007;Munns and Testter 2008). In those studies, many abiotic stress-inducible transcription factors have been identified, and their functions have been characterized.…”