Fig. 2

ΔmtDNA levels are selectively eliminated, and their adverse effects reversed in fzo-1(mut);+/ΔmtDNA animals across generations. A Schematic representation of the experimental setup. The fzo-1 heterozygotes progeny of heteroplasmic hermaphrodites (fzo-1(ht);+/ΔmtDNA) was identified and maintained using self-propagation and single worm genotyping to establish heteroplasmic lines carrying fzo-1(ht);+/ΔmtDNA. Progeny animals (generation 1; G1) were isolated, allowed to lay eggs, and their genotypes were determined. Heteroplasmic mutant fzo-1(mut);+/ΔmtDNA or wild type fzo-1(wt);+/ΔmtDNA progeny were then monitored over several generations (G2m-G4m and G2wt-G4wt, respectively). B The percent of gravid adults of fzo-1(mut);+/ΔmtDNA mutant progeny across generations (G1m-G4m) at the indicated times after egg laying (G1m N = 3, n = 40, G2m N = 4, n = 152, G3m N = 3, n = 155 and G4m N = 3, n = 82). Data were analyzed using Cox proportional-hazards regression (Additional file 1: Table S2). G2m and G3m were slower to reach adulthood than G1m (P < 0.001) but not G4m (P = 0.750). C The percent of hatched embryos of fzo-1(mut);+/ΔmtDNA progeny across generations (G2m N = 7, n = 236, G3m N = 6, n = 155 and G4m N = 4, n = 107) and the stable line (> 20 generations) fzo-1(mut);+/ΔmtDNA (N = 4, n = 93). Data are means ±1 standard error of the mean (1SE). Data were analyzed using one-way ANOVA followed by a Tukey’s post hoc test, (**) denotes P < 0.002 compared with G2m animals. D, E Box plot showing the percent of ΔmtDNA (N > 3 biological repeats) determined in individual animals (D) of the parental heteroplasmic strain +/ΔmtDNA (n = 23), the heteroplasmic fzo-1(mut) mutant cross-progeny strains (G1ht n = 13, G1m-G4m n = 20, 31, 21 and 21, respectively) and the progeny of G4m animals crossed with fzo-1(wt), (Gm→Gwt n = 21); (E) of the heteroplasmic fzo-1(wt) cross progeny strains (G1wt-G4wt n = 17, 20, 27 and 21, respectively). In the boxplot representation, center line, median; box limits, upper and lower quartiles; whiskers, minimum and maximum; points, data. Data were analyzed using Fractional regression (Additional file 1: Table S3). ΔmtDNA levels of G2m-G4m and Gm->Gwt were significantly lower than those of the parental heteroplasmic strain +/ΔmtDNA, (**) denotes P < 0.001. F The percent of ΔmtDNA determined for a population of animals from the stable cross lines (> 20 generations), fzo-1(wt);+/ΔmtDNA (N = 7), fzo-1(mut);+/ΔmtDNA (N = 3) and +/ΔmtDNA;fzo-1(Gm→Gwt) (N = 4). Data are means ±1 standard error of the mean (1SE). Data were analyzed using one-way ANOVA followed by a Tukey’s post hoc test, (**) denotes P < 0.001 compared with fzo-1(wt);+/ΔmtDNA animals. Individual data values are presented in Additional file 2