The 1D and 2D SDS-PAGE method was used to investigate the protein variation of salt tolerant suspension culture of rice grown within 0.5 and 5.0 mmol/L CaCl2. No difference of protein patterns among different treatments was found by 1D SDS-PAGE. Some differences of protein patterns could be resolved under 2D SDS-PAGE. One protein of 12.5 kD and pI 4.5 was found in all the suspensions except for the salt tolerant suspensions. This protein was more abundant in salt tolerant suspensions by supplemental 5.0 mmol/L CaCl2 than that by 0.5 mmol/L CaCl2. There was no difference between non-stressed suspensions in the presence and absence of 0.5 and 5.0 mmol/L CaCl2. One protein of 12.6 kD and pI 5.5 exists in all the treatments except for salt tolerant suspension by supplemental 5.0 mmol/L CaCl2. One protein of 13.0 kD and pI 5.9 only exists in non-stressed suspensions which could not be found in any other treatments. The production of three proteins (20.0 kD, pI 6.5; 22.0 kD, pI 6.5, and 22.0 kD, pI 6.3) was significantly inhibited by 5.0 mmol/L CaCl2. A group of five proteins (24.0 kD, pI 5.5; 24.5 kD, pI 5.65; 25.0 kD, pI 5.7; 25.5 kD, pI 5.55; 26.0 kD, pI 5.6) were enhanced by salt stress combined with calcium, especially with 5.0 mmol/L CaCl2. The other two proteins (31.0 kD, pI 5.5; 31.0 kD, pI 4.9) were also found much more abundant in salt tolerant suspensions in the presence of 0.5 and 5.0 mmol/L CaCl2, and are more enriched in the latter one. No any new specific protein was found to be correlated with the response to salt stress combined with 5.0 mmol/L CaCl2.

Key words: 1D SDS-PAGE, 2D SDS-PAGE, Oryza sativa L., protein, salinity, tolerance