Effect of "osmotic stress" on protein and nucleic acid synthesis in isolated tobacco protoplasts.

The incorporation of labeled precursors into RNAs and proteins of isolated tobacco (Nicotiana tabacum L.) leaf protoplasts decreases with increasing osmotic pressure in the incubation medium. The incorporation of precursors into RNA and proteins is linear for 15-18 h after the isolation of the protoplasts, irrespective of the osmolarity of the culture media. The uptake of precursors is also affected by the osmolarity of the medium. However, the osmotic stress-induced inhibition of incorporation of precursors into RNA and proteins is also apparent if the differences in uptake are taken into consideration in the calculation. Incorporation of (32)P into TMV-RNA is also inhibited by osmotic stress. As assayed by the double labeling ratio technique, osmotic stress has less unequivocal effect on TMV protein synthesis.