Control of protein synthesis during the development of Acetabularia

Proteins from the soluble, chloroplastic and cell membrane fractions of axenically grown Acetabularia were analysed by zone electrophoresis. Incorporation of [14C]leucine into different proteins was measured by autoradiographic analysis of the electrophoretic patterns. The protein patterns from the soluble fraction remain constant with respect to the number of detectable bands but change with respect to the relative synthetic rates at various developmental stages. The protein patterns from the membrane fraction change with respect to both the number of protein species and the relative synthetic rates. The analysis of the synthetic performance of enucleated cells revealed that most of the proteins from the soluble and the membrane fractions continue to be synthesized in the absence of the nucleus and that the changes that normally occur in the protein patterns of the membrane fraction at the time of cap formation also take place in enucleated cells. This is taken as an indication that the control of the synthesis of the proteins studied is of extranuclear nature. It was also found that chloroplasts are capable of synthesizing all the components of the chloroplastic protein spectrum at least 4 weeks after enucleation. Some of the chloroplastic proteins can also be synthesized by purified chloroplasts in extracellular conditions. The possibility of extranuclear control of protein synthesis being a rather general phenomenon during the development of Acetabularia is discussed.