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Abstract Mobile genetic elements (MGEs) are transient genetic material that can move either within a single organism's genome or between individuals or species. While historically considered “junk” DNA (i.e., deleterious or at best neutral), more recent studies reveal the potential adaptive advantages MGEs provide in lineages across the tree of life. Ciliates, a group of single‐celled microbial eukaryotes characterized by nuclear dimorphism, exemplify how epigenetic influences from MGEs shape genome architecture and patterns of molecular evolution. Ciliate nuclear dimorphism may have evolved as a response to transposon invasion and ciliates have since co‐opted transposons to carry out programmed DNA deletion. Another example of the effect of MGEs is in providing mechanisms for lateral gene transfer (LGT) from bacteria, which introduces genetic diversity and, in several cases, may drive ecological specialization in ciliates. As a third example, the integration of viral DNA, likely through transduction, provides new genetic materials and can change the way host cells defend themselves against other viral pathogens. We argue that the acquisition of MGEs through non‐Mendelian patterns of inheritance, coupled with their effects on ciliate genome architecture and persistence throughout evolutionary history, exemplify how the transmission of mobile elements should be considered a mechanism of transgenerational epigenetic inheritance.
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Inheritance through the cytoplasm
Abstract Most heritable information in eukaryotic cells is encoded in the nuclear genome, with inheritance patterns following classic Mendelian segregation. Genomes residing in the cytoplasm, however, prove to be a peculiar exception to this rule. Cytoplasmic genetic elements are generally maternally inherited, although there are several exceptions where these are paternally, biparentally or doubly-uniparentally inherited. In this review, we examine the diversity and peculiarities of cytoplasmically inherited genomes, and the broad evolutionary consequences that non-Mendelian inheritance brings. We first explore the origins of vertical transmission and uniparental inheritance, before detailing the vast diversity of cytoplasmic inheritance systems across Eukaryota. We then describe the evolution of genomic organisation across lineages, how this process has been shaped by interactions with the nuclear genome and population genetics dynamics. Finally, we discuss how both nuclear and cytoplasmic genomes have evolved to co-inhabit the same host cell via one of the longest symbiotic processes, and all the opportunities for intergenomic conflict that arise due to divergence in inheritance patterns. In sum, we cannot understand the evolution of eukaryotes without understanding hereditary symbiosis.
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- PAR ID:
- 10369024
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Heredity
- Volume:
- 129
- Issue:
- 1
- ISSN:
- 0018-067X
- Page Range / eLocation ID:
- p. 31-43
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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