Characterization of 3H-labeled supercoiled mitochondrial DNA from tobacco suspension culture cells

✍ Scribed by Sparks, R. B. ;Dale, R. M. K.

• Publisher: Springer
• Year: 1980
• Tongue: English
• Weight: 459 KB
• Volume: 180
• Category: Article
• ISSN: 0026-8925
• DOI: 10.1007/bf00425847

✦ Synopsis

Mitochondrial DNA of tobacco supension culture cells labeled in vivo with a H-thymidine was isolated from purified mitochondria. It has a density of 1.707 + 0.002 g/cm 3 unique from both nuclear and chloroplast DNA. Approximately 2545% of the mtDNA molecules from several preparations from suspension culture cells were isolated as supercoiled molecules from ethidium bromide-cesium chloride gradients. Electron microscopic examination of nicked supercoiled molecules revealed a heterogenous population of molecules ranging in size from 0.5 to 42 btm. The most abundant size class of 365 molecules measured was 9 ~tm. Restriction endonuclease digests of both supercoiled and open circular/linear molecules were essentially identical and yielded a minimum size estimate of 76 btm. The availability of large amounts of labeled covalently closed circular molecules will facilitate the resolution of the different size classes and allow, for the first time, a direct analysis of the relationships among the heterogenous population of DNA molecules found in plant mitochondria.