Effect of mitochondrial genes on development and differentiation in the cellular slime molds.

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1. RFLPs were used as markers to monitor mitochondrial DNA(mt DNA)inheritance in the cellular slime molds, Polysphondylium pallidum. The transmission of the mt DNA was uniparental. When two opposite mating types(matl and mat2)of closely related strains were crossed, all the haploid progeny regardless of mating types inherited their mt DNA from the mat2 parent only. However, when opposite mating types from more distantly related strains were crossed, most of the progeny also from the mat2 parent, but some inherited their mt DNA from the matl parent.2. About 10 kb of the mt DNA(54 kb)of the cellular slime mold, Dictyostelium discoideum, was sequenced. From the RNA and amino acid sequence comparison with the published sequences by computer analysis, the following genes were identified : ATPase subunit 9, NADH dehydrogenase subunit 1(nahl), NADH dehydrogenase subunit 3, NADH dehydrogenase subunit 6, cytochrome oxidase b(cob), ORF209 with unknown function, a part of one NADH dehydrogenase subunit(49 kDa), small RRNA, a part of large rRNA, and nine tRNAs(Arg, Asn, Cys, Gln, Lys, Met, f-Met, Pro, Trp). All the tRNAs have D-loop and T-loop region and the 2D-structure showed typical clover leaf figure. From the comparison of the ndhl and cob amino acid sequence with that of other organisms, it was supposed that, in the mt of D. discoideum, universal genetic code are used although some codons such as UGA and AGG did not appeared yet. In the sequenced region of the large RRNA gene, group-l-intron was found. ORF209 has a homologue in the chloroplast DNA of tobacco and liverwort as well as in the nuclear DNA of Synechocystis. In addition, the ORF209 has homologous region with the Pl protein encoded in Paramecium mt DNA. However, the mt DNA of animals higher than sea urchin did not have the corresponding gene.