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Title: ELECTROSTATIC CHANGES IN ROOT PLASMA MEMBRANE OF GLYCOPHYTIC AND HALOPHYTIC SPECIES OF TOMATO

Author
item Wilson, Clyde
item SOLIMAN, M - SOIL SALINITY LAB, EGYPT
item SHANNON, MICHAEL - US SALINITY LAB, RETIRED

Submitted to: Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/16/2004
Publication Date: 11/11/2005
Citation: Wilson, C., Soliman, M.S., Shannon, M.C. 2005. Electrostatic changes in root plasma membrane of glycophytic and halophytic species of tomato. Plant Science. 169:805-811.

Interpretive Summary: All living organisms are composed of either a single cell or many cell. These cells are enclosed by a plasma membrane made up of a variety of compounds. Some of these compounds have electrical charges, either positive or negative. Most membranes have a net abundance of negative charges giving the membrane a negative surface charge. It appears from our research that the magnitude to these negative charges are greatly reduced when the plant is grown in saline water. Our research showed that this reduction in negative charges due to saline water is much greater in the cultivated tomato than in its more salt-tolerant wild relative. Further investigations showed that this change in surface charge affects the way nutrients in the water interact with enzymes in the membrane. This may explain why some plants are more tolerant to salinity stress than other plants. Theoretical calculations indicate that the change in surface charge may affect the distribution of ions next to the root cell and thus, may affect the nutritional status of the plant.

Technical Abstract: We investigated the effect of salt stress on the electrostatic properties of plasma membrane vesicles from the glycophytic tomato, Lycopersicon esculentum (Mill, cfs Heinz 1350 and VF 36) and the halophytic, wild species, L. cheesmanii (Hook, C.H. Mull, ecotype 1401) grown under control and saline conditions. Fluorescence titration indicated that salinity stress modulated the plasma-membrane surface potential to more electro-positive values, but, a much smaller shift was measured in the halophytic tomato. BTP-Cl-stimulation of proton pumping was greater in vesicles isolated from control roots obtained from wild Lc-1401 as compared with the cultivated Heinz-1350. The reverse was true in vesicles isolated from salt-stressed roots. Cl-stimulated proton pumping to a greater degree in vesicles from Heinz-1350 than Lc 1401. In most cases, K+ stimulation of H+- pumping activity was higher in vesicles isolated from salt-stressed than from non-stressed plants. Coomassie blue stained SDS-PAGE of membranes from control and salt-stressed plants were similar. Salt stress suppressed a 41.4 kD protein band and induced the synthesis of a new peptide of 112.4 kD in all varieties and species of tomato. Polyclonal antibody cross-reacted with the ATPase subunits from control and salt-stressed plants. We could not conclude that there were any major differences in quantity of ATPase subunit relative to the amount of protein loaded on the gel.