Preliminary characterisation of DML1, an essential Saccharomyces cerevisiae gene related to misato of Drosophila melanogaster.

Abstract

A genetic and cell-biological analysis is provided for Saccharomyces cerevisiae DML1 (YMR211w) encoding a Drosophila melanogaster Misato-like protein. Misato and Dml1p are descendants of an ancestral tubulin-like protein, and exhibit regions with similarity to members of a GTPase family that include eukaryotic tubulin and prokaryotic FtsZ. Deletion of DML1 was lethal to haploid cells; sporulated DML1/dml1Delta heterozygotes from different genetic backgrounds gave rise to no more than two viable spores per tetrad. DAPI staining for DNA in combination with Southern analysis using the mitochondrial genes COX3, 15S_rRNA_2, and COB revealed that a significant portion of the surviving meiotic progeny were [rho(0)] lacking mtDNA. In addition, meiotic transmission of centromeric plasmids also appeared to be impaired. Self-complementation using extra-chromosomal copies of DML1 efficiently restored meiotic inheritance of mtDNA, but improved spore viability ratios only in part. Inheritance of mtDNA could also be restored using misato cDNA. Unscheduled expression of DML1 tethered to the inducible ADH2 promoter altered both mitochondrial dispersion and general cell morphology. We propose that Dml1p and Misato have been co-opted into a role in mtDNA inheritance in yeast, and into a cell division-related mechanism in flies, respectively. Dml1p might additionally function in the partitioning of the mitochondrial organelle itself, or in the segregation of chromosomes, thereby explaining its essential requirement.