ABSTRACT
Keywords: Functional genomics, Ion homeostasis, Salt stress, Salinity tolerance
1.1 Introduction / 2 1.2 Effects of Salinity on Plants / 2 1.3 Salt Tolerance Mechanism / 3
1.3.1 Ion Homeostasis: Transport Determinants and Their Regulation / 3 1.3.1.1 Na+ Influx / 3 1.3.1.2 Na+ Exclusion / 4 1.3.1.3 Na+ Sequestration / 5 1.3.1.4 Sodium Transport in the Whole Plant / 6
1.3.2 Osmotic Tolerance / 7 1.3.3 Antioxidant Regulation of Salinity Tolerance / 8
1.4 Plant Adaptation to Salinity: Genomic, Transcriptomic, Proteomic, and Metabolic Regulations / 9 1.4.1 Genomic Regulation / 9 1.4.2 Transcriptomic Regulation / 9 1.4.3 Proteomic and Metabolic Regulations / 10
1.5 Conclusions and Future Research Perspectives / 11 Acknowledgment / 11 References / 11
Salinity is one of the most serious factors limiting food production, because it limits crop yield with adverse effects on germination and restricts use of land previously uncultivated (Munns and Tester 2008). High salinity causes water stress, ion toxicity, nutritional disorders, oxidative stress, alteration of metabolic processes, membrane disorganization, reduction of cell division, and genotoxicity (Zhu 2002, 2007; Munns 2002). The complex “plant response to abiotic stress” involves many genes and biochemical molecular mechanisms. The analysis of the functions of stress-inducible genes is an important tool not only to understand the molecular mechanisms of stress tolerance and the responses of higher plants but also to improve the stress tolerance of plants by genomic strategies. The susceptibility or tolerance to high salinity stress in plants is a coordinated action of multiple stress-responsive genes, which also cross talk with other components of stress signal transduction pathways. Several types of gene belonging to different metabolic functions have been identified and used for over-expression into glycophytic plants to enhance salinity stress tolerance. The stress-related genes are generally classified into two major groups. The first one is involved in signaling cascades, transcriptional control, and the degradation of transcripts or proteins. The member of the second group functions in membrane protection and osmoprotection as antioxidants and as reactive oxygen species (ROS) scavengers (Pardo 2010). Plant responses to salinity and mechanisms conferring plant salinity tolerance have been studied for a long time. Using modern genetic approaches like genome sequencing, reverse genetics methods, and identification and characterization of key genes involved in salt-stress signaling, the understanding of salt tolerance mechanisms is substantially in progress especially salt ion signaling and transport (Hasegawa et al. 2000; Flowers 2004; Kosova et al. 2013). This chapter provides an overview of our current understanding of the mechanisms contributing to salt-stress tolerance in plants and the contribution of the genomic, transcriptomic, proteomic, and metabolic investigations to understand plant salinity tolerance.
