The developmental biochemistry of cotton seed embryogenesis and germination. VI. Levels of cytosol and chloroplast aminoacyl-tRNA synthetases during cotyledon development

Hybridization of bean chloroplast transfer RNAs to chloroplast DNA

Bean (Phaseolus vulgaris) chloroplast tRNAsLeu and tRNAsPhe hybridize to chloroplast DNA, whereas the corresponding cytoplasmic tRNA species do not, suggesting that chloroplast transfer RNAs are coded for by chloroplast DNA. The hybridization of the three chloroplast tRNAsLeu or of the two tRNAsPhe isoacceptors is not additive, and the isoacceptors compete with each other in the hybridization to chloroplast DNA, suggesting that these isoacceptors are coded for by the same gene(s) and differ only in the extent of post-transcriptional modification. Although hererologous aminoacylation reactions and comparisons of base composition suggest a resemblance between chloroplast and procaryotic tRNAs, only a slight cross hybridization reaction was observed between chloroplast and Escherichia coli leucyl- or phenylalanyl-tRNAs and DNAs.

Aminoacylation of Phaseolus vulgaris cytoplasmic, chloroplastic and mitochondrial tRNAsPro and tRNAsLys by homologous and heterologous enzymes

The cytoplasmic prolyl-tRNA synthetase can be separated by hydroxyapatite chromatography, from the enzyme present in the chloroplasts and in the mitochondria (organellar enzyme). The cytoplasmic lysyl-tRNA synthetase can also be separated from the organellar enzyme. There are two tRNAsPro in the cytoplasm; they can be charged by the cytoplasmic enzyme, but not by the organellar enzyme or the Escherichia coli enzyme. Chloroplasts contain, in addition to the two cytoplasmic tRNAsPro, one chloroplast-specific tRNAPro, which is not recognized by the cytoplasmic enzyme, but can be charged by the organellar or the E. coli enzyme. Mitochondria contain, in addition to the two cytoplasmic tRNAsPro, two mitochondria-specific tRNAsPro, which are not recognized by the cytoplasmic enzyme, but can be charged by the organellar or the E. coli enzyme. There are two tRNAsLys in the cytoplasm. Both can be charged by the cytoplasmic enzyme, but one can be charged by the organellar or E. coli enzyme. Chloroplasts contain in addition to one cytoplasmic tRNALys, one chloroplast-specific tRNALys which can only be charged by the organellar or E. coli enzyme. Mitochondria contain, in addition to one cytoplasmic tRNALys, one mitochondria-specific tRNALys which can only be charged by the organellar or E. coli enzyme.