A mathematical model of kinetoplastid mitochondrial gene scrambling advantage

We model and discuss advantages of pan-editing, the complex way of expressing mitochondrial genes in kinetoplastids. The rapid spread and preservation of pan-editing seems to be due to its concomitant fragment dispersal. Such dispersal prevents losing temporarily non expressed mitochondrial genes upon intense intraspecific competition, by linking non expressed fragments to parts which are still needed. We mathematically modelled protection against gene loss, due to the absence of selection, by this kind of fragment association. This gives ranges of values for parameters like scrambling extent, population size, and number of generations still retaining full genomes despite limited selection. Values obtained seem consistent with those observed. We find a quasi-linear correlation between dispersal and number of generations after which populations lose genes, showing that pan-editing can be selected to effectively limit gene loss under relaxed selective pressure.