Figure 1. Phenotypic effects of deleting all self-splicing introns from the S. cerevisiae mitochondrial genome.

Deletion of mitochondrial introns (I₀) or overexpression of Mss116 (Mss116_OE) (a) reduces growth rates, (b) extends chronological lifespan, (c) increases mitochondrial mass, measured as NAO fluorescence, (d,e) increases mitochondrial volume, (g) oxygen consumption, and (h) ATP levels but (i) decreases superoxide levels, measured as MitoSOX fluorescence. (f) Mitochondrial inner membrane potential does not differ significantly between strains. WT a161 and WT Y258 are control strains for I₀ and Mss116_OE, respectively, as described in the text. The Mss116^E268K strain harbours a mutant version of Mss116 that lacks ATPase activity. As a visual guide, strains are colored consistently throughout. Bar heights display the mean of three biological replicates, each calculated as the mean of three technical replicates. Error bars are standard errors of the mean. ***p<0.001; **p<0.01; *p<0.05 (ANOVA plus post hoc).

Figure 1—figure supplement 1. Competitive fitness is decreased in I₀ (competed against WT a161) and Mss116_OE (competed against the empty vector control WT Y258).

Bar height represents the mean of three biological replicates. Error bars are standard error of the mean. ***p<0.001; **p<0.01; *p<0.05 (ANOVA plus post hoc). See Materials and methods for details of how competitions were carried out and relative fitness determined.

Figure 1—figure supplement 2. I₀ and Mss116_OE show no qualitative difference in growth on (a) glucose and (b) glycerol.

Numbers on top of each panel represent the decimal dilution of the stationary culture that is plated as a spot of 5 µl.

Figure 1—figure supplement 3. Mss116 expression level is 2.5-fold increased in the Mss116_OE strain.

(a) GFP-tagged Mss116 localizes to mitochondria, whether expressed at endogenous levels (left image) or upon overexpression in the Y258 background (right image). (b) The expression level of Mss116 increases approximately 2.5-fold in the Mss116_OE strain, as measured by flow cytometry. Bar heights display the mean of three biological replicates, each of them representing mean of three technical replicates. Error bars are standard error of the mean. ***p<0.001; **p<0.01; *p<0.05 (ANOVA plus post hoc).

Figure 1—figure supplement 4. Median and maximum replicative lifespan of Mss116_OE is extended compared to the empty vector control and Mss116^E268K.

The total number of monitored mother cells is as follows: 90 cells for the empty vector control, 86 cells for Mss116_OE, and 91 cells for Mss116^E268K. Measurements were pooled across three independent experiments.