[The effect of rifampicin on the RNA- and protein synthesis as well as on the morphogenesis and on the chlorophyll content of nucleate and anucleate cells of Acetabularia].

Rifampicin (10μg/ml) strongly inhibits the incorporation of [5-(3)H]-uridine into the chloroplast RNA of anucleate cells of the green alga Acetabularia mediterranea, whereas incorporation into nuclear RNA is hardly affected.Furthermore, at a concentration range of 1-10[Symbol: see text]g/ml rifampicin has only a small effect on stalk- and cap formation in nucleate posterior parts of the stalk. As has already been shown, the morphogenesis of such cell segments depends on the synthesis of new RNA in the nucleus. Similarly rifampicin only slightly inhibits the synthesis of the enzyme UDPG-pyrophosphorylase, which is coded by nuclear DNA.These slight inhibitions are interpreted as secondary effects arising from a blockage of plastid RNA synthesis, since both nucleate and anucleate cells respond in a similar manner and to the same degree.In contrast the increase in the chlorophyll content in nucleate and anucleate cells is severely impaired by the antibiotic. These findings indicate that the nucleus and the plastids contain different DNA-dependent RNA-polymerases.