Polyacrylamide gel analysis of high molecular weight ribonucleic Acid from etiolated and green cucumber cotyledons

Ribosomes in the lutoïd fraction (=lysosomal compartment) from Hevea brasiliensis Künth. (Mull.-arg.) latex

Lutoïd ribosomes represent 11.9% of the total ribosomal content of latex from Hevea brasilensis. Their two high-molecular-weight RNA components are identified. When undegraded, their molecular weights are calculated to be 1.3×10(6) and 0.7×10(6). Their nucleotide base composition is determined. The occurrence of lutoïd membrane-bound ribosomes and the lability of the 1.3×10(6)RNA component are discussed in relation to the biological role of lutoïds, more generally of a lysosomal compartment in the cellular function.

Purification and quantitative changes of mitochondrial DNA in etiolated cucumber seedlings

The mtDNA (mitochondrial DNA) extracted from etiolated seedlings of Cucumis sativus L. has been purified by a three-step procedure: RNase and pronase treatment, bio-gel filtration, analytical CsCl gradient centrifugation. This procedure appeared rapid, suitable for small quantities of DNA and gave highly reproducible results. It was used to follow the quantitative variation of the mtDNA in hypocotyls and cotyledons of dark-grown cucumber seedlings.The major feature occurring during the etiolation process appeared to be an important accumulation of the mtDNA in hypocotyls between 3 and 5 days of culture. The amount of the mtDNA per hypocotyl increased 5 times, the hypocotyl length and the total DNA increased 6 and 12 times respectively, between these two stages. It was demonstrated that at least during the first week of culture in the dark, endogeneous hormone-induced elongation in the cucumber hypocotyl (a non-dividing tissue) was associated to an important accumulation of mtDNA.

Nucleic Acid Metabolism in Germinating Onion: I. Changes in Root Tip Nucleic Acid during Germination

Nucleic acid synthesis in the G(1) cell population of the 1-millimeter apex of the Allium cepa embryo was studied during the initial 73 hours of germination. Quantitative data indicate that the total amount of RNA per cell began to increase after 18 hours of germination while the initial DNA per cell increase did not occur until some 20 hours later. Polyacrylamide gel electrophoresis patterns of (3)H-uridine-labeled total nucleic acid samples indicated that synthesis of all detectable RNA fractions present in the pre-emergent 1-millimeter apex (i.e., cytoplasmic and "chloroplast-like" RNA) began at approximately the same time (18 hours). Synthesis of the various cytoplasmic RNA fractions continued throughout the germination period. Data indicating synthesis of the "chloroplast-like" RNA were obtained only for the initial 36 hours of germination. Specific radioactivity of (3)H-uridine-labeled total nucleic acid increased during the first 41.5 hours of germination but then decreased while the accumulation of RNA per cell continued to increase throughout the 73-hour period. In addition, a method is described which reduced the bacterial contamination of Allium seed to a level not detectable by incorporation of radioactive precursors into bacterial ribosomal RNA.