Jan 25, 2025 01:07 AM
https://www.eurekalert.org/news-releases/1071606
EXCERPT: . . . Sex is the driving force of evolution: It promotes genetic diversity and helps organisms to adapt more quickly to changing environmental conditions. Without sex, however, organisms risk genetic stagnation and extinction – at least according to prevailing evolutionary theory. Yet, the oribatid mite Platynothrus peltifer challenges this paradigm: It has existed for over 20 million years – entirely without sex. The asexual oribatid mites produce their female offspring from unfertilized eggs without males. Males are absent or extremely rare and do not contribute to the gene pool. Depending on the mechanism restoring the diploid set of chromosomes, offspring can inherit either all or some of the mother’s gene variants (alleles). They can therefore be ‘full clones’ of the mother.
In the oribatid mite, the two copies of the chromosome sets evolve independently of each other, allowing new genetic variants to emerge while also retaining important information. The team observed notable differences in gene expression – in other words, which copies of the genes are active and to what extent. These differences enable rapid responses to environmental changes and provide a selective advantage.
Another mechanism contributing to genetic diversity is horizontal gene transfer (HGT), i.e. the movement of genetic material outside of the confined barriers of sexual reproduction. “Horizontal gene transfer can be thought of as adding new tools to an existing toolbox. Some of these genes seem to help the mite to digest cell walls, thus expanding its food spectrum,” explained the study’s first author, Dr Hüsna Öztoprak from the University of Cologne’s Institute of Zoology.
Additionally, transposable elements (TE) or ‘jumping genes’, play an important role. TEs move within the genome like chapters in a book that are rearranged to change the course of the plot. The fact that the activity of these TEs differs between the two chromosome copies is particularly exciting. While they are active on one copy and thus can cause dynamic changes, they tend to remain rather inactive on the other.
The study provides new insights into the survival strategies of asexual organisms. Asexual evolution is supported by various sources of genetic diversity, to which the research team draws attention in the study. “In future research projects, we would like to find out whether there are additional mechanisms that might be important for evolution without sex,” said Dr Jens Bast, Emmy Noether group leader at the University of Cologne. (MORE - missing details, no ads)
EXCERPT: . . . Sex is the driving force of evolution: It promotes genetic diversity and helps organisms to adapt more quickly to changing environmental conditions. Without sex, however, organisms risk genetic stagnation and extinction – at least according to prevailing evolutionary theory. Yet, the oribatid mite Platynothrus peltifer challenges this paradigm: It has existed for over 20 million years – entirely without sex. The asexual oribatid mites produce their female offspring from unfertilized eggs without males. Males are absent or extremely rare and do not contribute to the gene pool. Depending on the mechanism restoring the diploid set of chromosomes, offspring can inherit either all or some of the mother’s gene variants (alleles). They can therefore be ‘full clones’ of the mother.
In the oribatid mite, the two copies of the chromosome sets evolve independently of each other, allowing new genetic variants to emerge while also retaining important information. The team observed notable differences in gene expression – in other words, which copies of the genes are active and to what extent. These differences enable rapid responses to environmental changes and provide a selective advantage.
Another mechanism contributing to genetic diversity is horizontal gene transfer (HGT), i.e. the movement of genetic material outside of the confined barriers of sexual reproduction. “Horizontal gene transfer can be thought of as adding new tools to an existing toolbox. Some of these genes seem to help the mite to digest cell walls, thus expanding its food spectrum,” explained the study’s first author, Dr Hüsna Öztoprak from the University of Cologne’s Institute of Zoology.
Additionally, transposable elements (TE) or ‘jumping genes’, play an important role. TEs move within the genome like chapters in a book that are rearranged to change the course of the plot. The fact that the activity of these TEs differs between the two chromosome copies is particularly exciting. While they are active on one copy and thus can cause dynamic changes, they tend to remain rather inactive on the other.
The study provides new insights into the survival strategies of asexual organisms. Asexual evolution is supported by various sources of genetic diversity, to which the research team draws attention in the study. “In future research projects, we would like to find out whether there are additional mechanisms that might be important for evolution without sex,” said Dr Jens Bast, Emmy Noether group leader at the University of Cologne. (MORE - missing details, no ads)