ALTERATION OF GENE-EXPRESSION IN TOMATO PLANTS (LYCOPERSICON-ESCULENTUM) BY DROUGHT AND SALT STRESS

The effect of drought and NaCl treatments on polypeptide levels in both roots and leaves of tomato (Lycopersicon esculentum) seedlings was analyzed using two-dimensional polyacrylamide gel electrophoresis. In roots, comparison of silver-stained protein patterns showed that during drought treatment two proteins were highly accumulated and after rehydration they returned to the control level. The same changes were also observed under salinity stress. Moreover, salt treatment induced stress-specific proteins. In leaves, the in vivo labelling of intact leaves with S-35-labelled methionine showed that drought stress resulted in progressive changes in the protein pattern. There is de novo synthesis of proteins and repression of preexisting protein synthesis. The time course of appearance of newly synthesized proteins was different during water stress. The changes in proteins were usually reversible after rehydration of the seedlings. Leaves of NaCl-treated plants did not synthesize any salt stress specific polypeptides, but the synthesis of several drought-modulated proteins was affected. It is suggested that the quantitative and qualitative changes in protein synthesis may contribute to stress-resistant or stress-injury mechanisms.