Robert J. Spreitzer

True reversion of a mutation in the chloroplast gene encoding the large subunit of ribulosebisphosphate carboxylase/oxygenase in Chlamydomonas.

The ribulosebisphosphate carboxylase/oxygenase-defective Chlamydomonas mutant, 10-6C, was the first mutant to be physically defined in chloroplast DNA. In this report, a photosynthesis-competent revertant of the 10-6C mutant has been found to result from true reversion within the chloroplast large-subunit gene. This result supports the original assignment of the 10-6C mutation within the large-subunit gene.

Structure and Expression of Chloroplast and Nuclear Genes in Chlamydomonas reinhardii

Chlamydomonas reinhardii, a facultative photoautotroph, can also be grown heterotrophically on acetate in the dark. Thus, mutants impaired in photosynthetic functions can be recovered as acetate requirers and their specific defects analyzed. While a part of the genetic information necessary for chloroplast function is found in the nucleus and displays classical Mendelian inheritance, another part is found in the chloroplast and undergoes non-Mendelian, uniparental transmission. In the occasional biparental zygotes, chloroplast gene markers can be observed to recombine. This unique property of Chlamydomonas has led to the derivation of a formal genetic map of the chloroplast genome (Sager 1972; Gilharn 1978). An extensive nuclear genetic map also exists (Harris 1982).