Artificially induced fusions between Chlamydomonas reinhardtii and Chlamydomonas smithii. Transmission of non-mendelian traits in the fusion products

Abstract Artificial fusions between protoplasts of Chlamydomonas smithii ( mt + ) and protoplasts of Chlamydomonas reinhardtii ( mt + or mt − ) containing complementing biochemical nuclear mutations and extrachromosomal antibiotic resistance mutations have been performed. The cells of the colonies resulting from mitotic division of the fusion products were demonstrated to be diploid and morphologically identical to cells issued from diploid vegetative zygotes obtained from sexual crosses between the two species. The transmission of antibiotic resistance genes in the products resulting from fusions or crosses was similar to that observed in products obtained from fusions or crosses between C. reinhardtii mutant strains, indicating that the antibiotic resistance markers were most probably residing in the chloroplast genome. The transmission of the capacity to grow in the dark on media containing acetate - a property of C. reinhardtii cells but not of C. smithii cells - was also analyzed in the diploid products. The results showed that this trait was transmitted according to a non-Mendelian fashion, different from that observed for chloroplast markers. The possibility that this property is under control of the mitochondrial genome is discussed.