Chloroplast DNA recombination in interspecific hybrids of Chlamydomonas : Linkage between a nonmendelian locus for streptomycin resistance and restriction fragments coding for 16S rRNA

Abstract

Differences in the distribution of Ava I and BstEII restriction sites in the chloroplast DNA (cpDNA) of Chlamydomonas eugametos and C. moewusii have been used to detect extensive cpDNA recombination in the hybrid progeny of these interfertile algae. In the present study, the inheritance of these restriction-site differences was tested for recombina- MATERIALS AND METHODSStrains. The mt' wild-type strain of C. moewusii (UTEX 97), the male (mt') strain of C. eugametos (UTEX 9), and the mt' strain of C. eugametos carrying the nonmendelian streptomycin resistance mutation sr-2 (5) were provided by C. S. Gowans (University of Missouri-Columbia). The C. moewusii nonmendelian mutant er-nMJ, resistant to erythromycin (400 ,g/ml), was isolated from the mt( wild-type strain after methyl methanesulfonate mutagenesis. The mendelian mutant of C. moewusii requiring nicotinamide at 1 ,ug/ml (nic-J) and the other requiring p-aminobenzoic acid at 1 ,ug/ml (pab-J) were isolated from the mt-wild-type strain (UTEX 96) after UV mutagenesis; both mendelian mutations are unlinked to the Mnt locus. The mt' wild-type strain of C.

Interspecific chloroplast recombination in a Nicotiana somatic hybrid

“…Chloroplast genetics, however, is relatively unexplored. In the unicellular alga Chlamydomonas, genetic studies have been limited to segregation and recombination of genetic markers (2); physical evidence for chloroplast recombination is recent (3,4). In flowering plants chloroplast segregation has been extensively studied in species in which chloroplasts are biparentally inherited (2).…”

Nonreciprocal recombination between alleles of the chloroplast 23S rRNA gene in interspecific Chlamydomonas crosses

“…Reciprocal crosses were performed between C. eugametos with a non-Mendelian mutation for resistance to streptomycin (sr-2') and C. moewusii with a non-Mendelian mutation for resistance to erythromycin (er-nMY). The sr-2 locus has already been shown to map to the chloroplast 16S rRNA gene (13), whereas the er-nMl locus is shown in the present study to map to the chloroplast 23S rRNA gene. In order to enhance the detection of hybrids recombinant for the physical markers examined, cells were selected that contained the antibiotic-resistance allele derived from the mU parent, the parent that normally contributes fewer cpDNA molecules.…”

“…However, survival of these meiotic products is low, with fewer than 10o giving viable progeny (11,12). Virtually all hybrid lines recovered after meiotic germination and the completion of sorting out (about 20 mitotic generations) have proven to be homoplasmic for recombinant cpDNA digestion patterns; i.e., all ofthe multiple cpDNA copies in each cell appear identical (13). Most fragment markers in these recombinant patterns were derived from the mating-type-plus (mt') parent, a result consistent with the observation that there is preferential destruction of cpDNA derived from the matingtype-minus (mtU) parent during the mating process (14,15).…”

Extensive restriction fragment length polymorphisms in a new isolate ofChlamydomonas reinhardtii

“…Extensive restriction fragment length polymorphisms in the S1-D2 strain relative to either C. reinhardtii or C. smithii are revealed by using various gene probes for both the organdie and nuclear genomes. RFLP analysis has proven useful in Chlamydomonas in the study of organelle genomes (Lemieux et al 1980(Lemieux et al , 1984Boynton et al 1987) and nuclear genomes (Ranum et al 1987) (Ranum et al manuscript in preparation). The new strain, S1-D2, offers some additional advantages for mapping studies.…”

“…RFLPs to study the inheritance of the chloroplast genome in Chlamydomonas have been described using the species moewusii and eugametos (Lemieux et al 1980(Lemieux et al , 1984. (Hoshaw and Ettl 1966) have been used in studies of inheritance of both the mitochondrial and chloroplast genomes , and in experiments to map cloned genes in the nuclear genome (Ranum et al 1987;Ranum et al manuscript in preparation).…”