Synthetic lethal interaction between the pel1 and op1 mutations in Saccharomyces cerevisiae

The Saccharomyces cerevisiae mutant strain containing the op1 mutation affecting the function of a mitochondrial ATP/ADP translocator has been crossed to the pel1 and crd1 mutants deficient in the biosynthesis of mitochondrial phosphatidylglycerol (PG) and cardiolipin (CL). Using tetrad analysis of diploids issued from corresponding crosses a synthetic lethal interaction has been observed between the op1 and pel1 mutations resulting in the lack of growth of a corresponding double mutant on minimal medium containing glucose. The op1 pel1 double mutant also displayed a decreased susceptibility to fluconazole and a compromised growth even in complex medium containing glucose. The viability of mutant cells was strongly reduced, corresponding to <30 % and 10 % of colony-forming units observed after growth in complex and minimal medium, respectively. A lower viability of the double mutant in minimal medium was accompanied by an increased formation of mitochondrial petite mutants (as determined by mtDNA rescue into diploid cells). The results indicate that in the simultaneous absence of mitochondrial anionic phospholipids (PG plus CL) and ATP/ADP exchange across the inner mitochondrial membrane the yeast mitochondrial functions are severely limited, leading to a strongly compromised cell multiplication. Since under similar conditions the op1 crd1 double mutant was able to grow on minimal medium this deleterious effect of anionic phospholipid deficiency could be at least partially substituted by PG accumulated in the cardiolipin deficient delta crd1 mutant cells.