Mechanisms for salt tolerance and susceptibility in tomato
High soil salinity affects agricultural production in many parts of the world with a third of all irrigated land estimated to be affected. Salt induced changes in protein accumulation are one of the means for identifying salt tolerance or sensitivity in plants. To study the mechanisms for salt tolerance or susceptibility in plants, two tomato cultivars, Solanum lycopersicum L. cv. Walter (salt sensitive) and S. lycopersicum L. var. cerasiforme (salt tolerant) were used for this experiment. Seedlings were grown in half-strength Hoagland hydroponic solutions with pH ranging from 6-6.5. The plants were treated with 200mM NaCl (Fisher) while control plants were supplemented with only half-strength Hoagland solution. Three biological replicates of young leaves, matured leaves and roots were sampled two days after treatment. Visual observations of the plants showed growth inhibition of salt treated tomato plants as compared to control plants. Mineral analysis showed a differential accumulation of Na and Cl between the two cultivars. Roots of the sensitive cultivar showed a 33.5 fold change in Na between treated and nontreated plants while the tolerant cultivar showed only 9.2 fold change. Two-dimensional difference gel electrophoresis 2-D DIGE and Isobaric tags for relative and absolute quantitation (iTRAQ) proteomic analysis were used to identify proteins significantly altered due to salt treatment. Many proteins associated vital cellular processes such as metabolism (Phosphoenolpyruvate carboxylase induced in sensitive cultivar but down-regulated in tolerant cultivar), photosynthesis (Suppressed Chloroplast Rubisco activase in both species), and defense (induced antioxidant proteins glutathione S-transferase and peroxidase in both species), were altered. Important transcription factors such as ASR4 and calmodulin known to encode components of signal transduction pathways involved in adaptation to water stress were significantly induced in the roots of the salt tolerant cultivar. Ion transport proteins such as H-ATPase involved in regulating Na+/K+ ion homeostasis were also induced in both species. Findings in this study therefore suggest that differential up/down regulation of enzymes responsible for important cellular pathways between the two cultivars is responsible for salt tolerance or sensitivity.
Molecular biology|Plant sciences
"Mechanisms for salt tolerance and susceptibility in tomato"
ETD Collection for Tennessee State University.