Co-evolution of the mitotic and meiotic modes of eukaryotic cellular division

TL;DR

This paper models the co-evolution of mitosis and meiosis in eukaryotic cells using a network approach, highlighting how the balance between these division modes depends on a key parameter and supporting the idea that meiosis evolved to enhance nuclear DNA diversification.

Contribution

Introduces a hypergraph-based network model for the co-evolution of mitotic and meiotic division modes, emphasizing the role of a key parameter in their coexistence.

Findings

The parameter λ determines which division mode prevails.

Both ncDNA and mtDNA diversification parameters influence evolutionary pathways.

Results support the hypothesis that meiosis evolved to boost ncDNA diversity.

Abstract

The genetic material of a eukaryotic cell comprises both nuclear DNA (ncDNA) and mitochondrial DNA (mtDNA). These differ markedly in several aspects but nevertheless must encode proteins that are compatible with one another. Here we introduce a network model of the hypothetical co-evolution of the two most common modes of cellular division for reproduction: by mitosis (supporting asexual reproduction) and by meiosis (supporting sexual reproduction). Our model is based on a random hypergraph, with two nodes for each possible genotype, each encompassing both ncDNA and mtDNA. One of the nodes is necessarily generated by mitosis occurring at a parent genotype, the other by meiosis occurring at two parent genotypes. A genotype's fitness depends on the compatibility of its ncDNA and mtDNA. The model has two probability parameters, $p$ and $r$, the former accounting for the diversification of ncDNA during meiosis, the latter for the diversification of mtDNA accompanying both meiosis and mitosis. Another parameter, $\lambda$, is used to regulate the relative rate at which mitosis- and meiosis-generated genotypes are produced. We have found that, even though $p$ and $r$ do affect the existence of evolutionary pathways in the network, the crucial parameter regulating the coexistence of the two modes of cellular division is $\lambda$. Depending on genotype size, $\lambda$ can be valued so that either mode of cellular division prevails. Our study is closely related to a recent hypothesis that views the appearance of cellular division by meiosis, as opposed to division by mitosis, as an evolutionary strategy for boosting ncDNA diversification to keep up with that of mtDNA. Our results indicate that this may well have been the case, thus lending support to the first hypothesis in the field to take into account the role of such ubiquitous and essential organelles as mitochondria.