Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2009
Publication Date: 3/1/2009
Citation: Suping, Z., Zhou, S., Fish, T., Thannhauser, T.W. 2009. Salt Induced and Salt Suppressed Proteins in Tomato Leaves. Journal of the American Society for Horticultural Science. 134(2):289-294. Interpretive Summary: Soil salinity is a worldwide threat to irrigated vegetable and other crop production. The cultivated tomato is classified as a moderately salt sensitive plant that is ideal as a model system in which to study salt stress. When grown in saline media, tomato production is reduced by 50% when the saturation extract reaches moderate levels. The performance of tomato plants under salt stress is regulated by a complex genetic mechanism. Plants perceive and respond to stressful conditions by altering their gene and protein expression causing parallel physiological and biochemical modulations. The objective of this study was to identify salt-regulated proteins using a comparative analysis between NaCl treated and non-treated leaves. Based on the putative functions of the proteins identified whose expression correlated with salt stress, the following conclusions were drawn: 1) In leaves of salt-treated tomato plants, ferredoxin-thioredoxin-reductase and quinone oxidoreductase were activated to alleviate oxidative stress and to detoxify toxic molecules generated by the stress. 2) Rubisco activase was suppressed; this could lead to reduction in carbon fixation and glucose synthesis. 3) UDP-glucose pyrophosphorylase was induced, but the UDPG products appeared to be more likely used for the synthesis of cell wall materials instead of sucrose and starch.
Technical Abstract: Tomato (Solanum lycopersicum cv. Money Maker) seedlings at the two-leaf stage were grown in one-half strength Hoagland solution supplemented with 50 mM NaCl for 4 days, with 100 mM NaCl for 4 days, with 150 mM NaCl for 4 days, and with a final concentration 200 mM NaCl for 2 days. Solutions were refreshed every 2 days for treated and untreated seedlings. Non-treated plants were grown in nonamended one-half strength Hoagland solution. Three biological replicates (BR) were included for treated and control experiments. At the end of treatments, the uppermost three newly expanded leaves from all 12 plants in each BR were collected and bulked to extract total protein. Proteomic analysis resulted in the identification of several salt-induced and salt-suppressed proteins. Saltinduced proteins were: vacuolar H+-ATPase A1 subunit isoform (1.6-fold), germin-like protein (1.5-fold), ferredoxin-NADP (+) reductase (1.2-fold), quinone oxidoreductase-like protein (4.4-fold), heat-shock protein (4.9-fold), and pyrophosphorylase (1.7-fold). Salt-suppressed proteins were: ATPase alpha subunit (–1.5-fold) and rubisco activase (–1.4-fold). Proteins identified in this study affect cellular activities for antioxidant, stress protection, carbon fixation, and carbohydrate partitioning in young tomato leaves under salt stress.