Post-maturation of the plastid ribosomal RNA in the plant kingdom.

The in vivo fragmentation of the plastid rRNA from plants situated at different places in the evolutionary sclae, with the exception of Algae, was analysed by electrophoresis using fully denaturing conditions. This fragmentation corresponds to an in vivo post-maturation. It exists only in some bacteria and is not random. Five main groups of fragments with the following real molecular weights (Mr) are found in 23 S: ca 0.9 x 10(6); 0.7 x 10(6); 0.45 x 10(6); 0.35 x 10(6) and 0.15 x 10(6). The existence of a large fragment (Mr = 0.9 x 10(6)) corresponds to a primitive type of fragmentation found in some archaic plants. Dicotyledons and several other groups have the same pattern of 23 S fragmentation, often comprising all the fragments mentioned above, whilst Graminaceae (Monocotyledons) constitute a special group with a very predominant 0.35 x 10(6) dalton fragment and the absence of the 0.45 x 10(6) dalton fragment. The plastid 16 S rRNA in all plants studied here has a Mr of 0.54 x 10(6) which is smaller than the 16 S of Escherichia coli taken as reference (0.56 x 10(6) dalton).