RESUMEN
While uniparental transmission of mtDNA is widespread and dominating in eukaryotes leaving mutation as the major source of genotypic diversity, recently, biparental inheritance of mitochondrial genes has been demonstrated in reciprocal crosses of Pelargonium zonale and P. inquinans. The thereby arising heteroplasmy carries the potential for recombination between mtDNAs of different descent, i.e. between the parental mitochondrial genomes. We have analyzed these Pelargonium hybrids for mitochondrial intergenomic recombination events by examining differences in DNA blot hybridization patterns of the mitochondrial genes atp1 and cob. Further investigation of these genes and their flanking regions using nucleotide sequence polymorphisms and PCR revealed DNA segments in the progeny, which contained both P. zonale and P. inquinans sequences suggesting an intergenomic recombination in hybrids of Pelargonium. This turns Pelargonium into an interesting subject for studies of recombination and evolutionary dynamics of mitochondrial genomes.
Asunto(s)
ADN Mitocondrial/metabolismo , Genoma Mitocondrial , Patrón de Herencia , Mitocondrias/genética , Pelargonium/genética , Recombinación Genética , Secuencia de Bases , Quimera/genética , Quimera/metabolismo , Cruzamientos Genéticos , ADN Mitocondrial/genética , ADN de Plantas/genética , ADN de Plantas/metabolismo , Genes de Plantas , Pelargonium/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Reacción en Cadena de la Polimerasa/métodos , Polimorfismo Genético , Especificidad de la EspecieRESUMEN
Plastidial (pt) and mitochondrial (mt) genes usually show maternal inheritance. Non-Mendelian, biparental inheritance of plastids was first described by Baur (Z Indukt Abstamm Vererbungslehre 1:330-351, 1909) for crosses between Pelargonium cultivars. We have analyzed the inheritance of pt and mtDNA by examining the progeny from reciprocal crosses of Pelargonium zonale and P. inquinans using nucleotide sequence polymorphisms of selected pt and mt genes. Sequence analysis of the progeny revealed biparental inheritance of both pt and mtDNA. Hybrid plants exhibited variegation: our data demonstrate that the inquinans chloroplasts, but not the zonale chloroplasts bleach out, presumably due to incompatibility of the former with the hybrid nuclear genome. Different distribution of maternal and paternal sequences could be observed in different sectors of the same leaf, in different leaves of the same plant, and in different plants indicating random segregation and sorting-out of maternal and paternal plastids and mitochondria in the hybrids. The substantial transmission of both maternal and paternal mitochondria to the progeny turns Pelargonium into a particular interesting subject for studies on the inheritance, segregation and recombination of mt genes.