Multiple biotic and abiotic environmental factors may constitute stresses that affect plant growth and yield in crop species. With a focus on ionic stress exerted by the presence of sodium, and the associated water deficit, recent advances in our understanding are reviewed. Established physiological, biochemical, and genetic approaches are made more meaningful by the inclusion of genomics-type tools, which have been most helpful by making available a global view of transcriptome responses to salinity stress, and by providing lines from the global mutagenesis of model species, in particular for Arabidopsis thaliana. Many of the genetic elements that assure ion homeostasis and ion transport have become known, as have several elements that control ion homeostasis. Genes that respond to salinity stress have been identified through mutant screens, from comparative functional studies that relied on known physiological and phenotypic parameters. Until now, the resulting concepts and strategies for engineering salinity stress tolerance in their majority targeted single genes in biochemical pathways, which represent end points of response cascades, but engineering of upstream master switches that regulate the activity of many downstream genes and proteins is increasingly attempted. The rapidly growing body of results on (salinity) stress sensing and signaling promises to lead to the identification of those genes that are of superior significance in salt stress response pathways, and abiotic stresses in general.
Key Words: Abiotic stresses, Ion homeostasis, Osmotic adjustment, Stress engineering, Abscisic acid, Biochemical pathways, Stress sensing, Stress signaling pathways.
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