Heteroplasmic suppression of an amber mutation in theChlamydomonaschloroplast gene that encodes the large subunit of ribulosebisphosphate carboxylase/oxygenase

✍ Scribed by Robert J. Spreitzer; Chris J. Chastain

• Publisher: Springer-Verlag
• Year: 1987
• Tongue: English
• Weight: 543 KB
• Volume: 11
• Category: Article
• ISSN: 0172-8083
• DOI: 10.1007/bf00393924

✦ Synopsis

The 18-5B and 18.7G mutants of Chlamydomonas reinhardtii lack ribulosebisphosphate carboxylase/ oxygenase holoenzyme and contain nonsense mutations in the chloroplast gene that encodes the protein's large s ubunit. Spontaneous revertants of the 18-5B opal (UGA) mutant were found to be heteroplasmic in a previous study (Spreitzer et al. 1984). They appeared to contain both mutant and wild-type alleles of a suppressor gene within the chloroplast. However, revertants of the 18-7G amber (UAG) mutant could not be recovered spontaneously. In the present investigation, revertants of the opal and amber mutants were recovered after a mutagen treatment. Heteroplasmic suppression of the 18-7G amber mutant was observed, suggesting that heteroplasmic suppression may be a common genetic mechanism of polyploid genomes. Although a diversity of other revertant types was also observed, no significant alteration occurred in the oxygen sensitivity of ribulosebisphosphate carboxylase acitivity.