Preferential synthesis of mitochondrial DNA during the initial stage of tissue growth in potato [Solanum tuberosum] explant cultures
1994
Masuda, K. (Hokkaido Univ., Sapporo (Japan). Faculty of Agriculture) | Kikuta, Y. | Fujino, K. | Okazawa, Y.
The DNA synthesized during the initial stage of tissue growth in culture of explants from potato tubers was characterized. An appreciable in corporation of radioactive thymidine into DNA was detected within 4 h of culture, and this increased moderately until 7 h. The incorporation then started to rise sharply, showing the first maximum at 18 h. Density gradient centrifugation of DNA in CsCl indicated that the label before 7 h was incorporated selectively into a heavy satellite DNA with a density ranging from 1,700 g.cm(-3) to 1.712 g.cm(-3). This range encompasses the density of mitochondrial DNA and rDNA for the potato. The synthesis of bulk DNA displaying main band at 1.694 g.cm(-3) was initiated at 7 h. The Bam HI digest from the early synthesized DNA was shown to contain fragments of mitochondrial DNA by comparative analysis upon agarose gel electrophoresis and fluorography. There was no significant change in the copy number for rDNA. Reassociation experiments demonstrated that the DNA labeled before 7 h of culture represented at least two kinetic components comprising repeated DNA sequences. These results suggest that preferential replication of mitochondrial DNA occurs during the initial stage of tissue growth in culture of explants from potato tubers
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