SALT-INDUCED SYNTHESIS OF NEW PROTEINS IN THE ROOTS OF RICE VARIETIES

Ten-day-old seedlings of rice (Oryza sativa L., varieties c.v. (Nona b okra, Basmati, IR28, and IR29) grown on MS medium were used in this st udy. Total protein extract from roots of control and 2% salt-treated p lants were analyzed by two dimensional electrophoresis. Following eigh t hours of salt stress including terminal three hours of in vivo label ing, two new proteins of molecular weights corresponding to 27 and 25. 5 kD were detected. These proteins were not detectable with silver sta ining after one day of stress but became evident after two days of sal t treatment and gradually increased up to four days. During recovery a fter two days of treatment, their levels decreased gradually and were present even after two days of recovery, though, in decreased amounts. No such protein was induced in plants stressed with copper (Cu), cadm ium (Cd), heat, ABA, or PEG treatments. Quantitative changes in the am ount of other proteins were also observed. This indicates that the ric e plant may adjust to the changes in its ionic environment by altering its macromolecular composition of root tissue.