Protein synthesis stimulated in sonicated sugar beet cells and protoplasts

Sugar beet suspension cells and protoplasts were exposed to 20 kHz ultrasound and the amount of 35S-methionine incorporated into cellular protein was determined after 2 days of culture. The incorporation of 35S-methionine in cells was enhanced up to 90% after sonication for 220–770 ms at 1.2–3.5 W/cm 2 which reduced viability 5–11% and decreased the average size of cell aggregates. In protoplasts, the 35S-methionine incorporation was increased up to 31% after sonication for 220–550 ms at 0.3–1.0 W/cm 2 with a concomitant reduction in viability of 10–16%. At higher ultrasonic energies, 35S-methionine incorporation declined proportionally to the reduction in protoplast viability. At concentrations up to 30 mM, cystamine and cysteamine did not affect 35S-methionine incorporation or viability of the sonicated protoplasts. These results show that mild ultrasonic irradiation can stimulate protein synthesis in plant cells and protoplasts significantly.