Representation of genomic kinetic sequence classes and sequence complexities were investigated in nuclear and polysomal RNA of the higher plant Petroselinum sativum (parsley). Two different methods indicated that most if not all polysomal poly(A) -RNA is transcribed from unique sequences. As measured by saturation hybridization in root callus and young leaves 8.7% and 6.2%, respectively, of unique DNA were transcribed in mRNA corresponding to 13.700 and 10.000 average sized genes. Unique nuclear DNA hybridized with an excess of polysomal poly(A)mRNA to the same extent as with total polysomal RNA. 3H-cDNA - poly(A)mRNA hybridization kinetics revealed the presence of two abundance classes with 9.200 and about 30 different mRNAs in leaves and two abundance classes with 10.500 and 960 different mRNAs in callus cells. The existence of plant poly(A)hnRNA was proven both by its fast kinetics of appearance, its length distribution larger than mRNA, and its sequence complexity a few times that of polysomal RNA.

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The DNA-dependent RNA polymerase of the blue-green alga Anacystis nidulans was reconstituted from its isolated subunits in the absence of urea. Applying this technique the kinetics and the subunit requirements of the reconstitution process were analyzed. The results reveal differences with respect to the reconstitution of Escherichiu coli polymerase.Reconstitution proceeds much more slowly in the case of the A . nidulans enzyme. Reconstitution here is absolutely dependent on the presence of the subunit 6. On the other hand, the largest of the subunits of M , = 190000 can be fully substituted by a specific degradation product of this subunit OfM, = 175000.Heterologous reconstitution between subunits of E. coli and A . nidulans polymerase does not result in active enzyme hybrids, showing a divergent evolution of the structure of this enzyme in these procaryotic organisms.

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