Gene expression in Acetabularia. III. Comparison of stained cytosolic proteins and in vivo and in vitro translation products

A comparison of stained cytosolic proteins, in vivo 80 S ribosome translation products and in vitro translation products of poly(A)+ RNA from three species of Acetabularia was performed after characterization of their molecular weights and isoelectric points via two−dimensional electrophoresis. A total of 803 stained proteins, and 121 in vivo and 77 in vitro translation products, representing the most abundant proteins in each category, were analysed. In interspecies comparisons, approximately 10% of the stained proteins were common to all three species and more than 50% were found to be species−specific. Approximately 25% of the in vivo translation products were common to all three species and more than 30% were found to be species−specific. The majority of the in vivo and in vitro translation products were detected by one or both of the other methods employed. Even though the analysis was limited to the most abundant proteins detected by each of the three methods and to one stage of development, the results suggest that the translation of some proteins is not regulated, that the in vivo translation of others, whose mRNA is present and translated in vitro, is turned off while the translation in vivo of others is enhanced relative to the total. This feature makes them candidates for stage−specific proteins. The results provide a firm basis for the extended analysis of the biological activity of heterologous messenger RNA in Acetabularia cytoplasm and for a more complete cataloguing of the mRNA population and translational activity at different stages in the development of Acetabulari