  Mitochondria in plant cells form strikingly dynamic populations of largely
individual organelles. Each mitochondrion contains on average less than a full
copy of the mitochondrial DNA (mtDNA) genome. Here, we asked whether
mitochondrial dynamics may allow individual mitochondria to `collect' a full
copy of the mtDNA genome over time, by facilitating exchange between
individuals. Akin to trade on a social network, exchange of mtDNA fragments
across organelles may lead to the emergence of full `effective' genomes in
individuals over time. We characterise the collective dynamics of mitochondria
in \emph{Arabidopsis thaliana} hypocotyl cells using a recent approach
combining single-cell timelapse microscopy, video analysis, and network
science. We then use a quantitative model to predict the capacity for the
sharing and accumulation of genetic information through the networks of
encounters between mitochondria. We find that biological encounter networks are
strikingly well predisposed to support the collection of full genomes over
time, outperforming a range of other networks generated from theory and
simulation. Using results from the coupon collector's problem, we show that the
upper tail of the degree distribution is a key determinant of an encounter
network's performance at this task and discuss how features of mitochondrial
dynamics observed in biology facilitate the emergence of full effective
genomes.
