Genome Size Changes by Duplication, Divergence, and Insertion in Caenorhabditis Worms
Paula E Adams1,2, Victoria K Eggers3, Joshua D Millwood1
1Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL, USA.
Molecular Biology and Evolution
|February 22, 2023
Summary
Genome size variation in nematodes is not driven by genome shrinkage or transposable elements. Instead, reproductive mode influences genome evolution through small structural mutations and gene changes.
Area of Science:
- Genomics
- Evolutionary Biology
- Nematology
Background:
- Genome size variation remains poorly understood, despite being measurable since the 1940s.
- Caenorhabditis nematodes exhibit conserved chromosome numbers but significant genome size differences between species.
- Androdioecy, a reproductive system with males and hermaphrodites, evolved multiple times in nematodes, with varying impacts on genome size.
Purpose of the Study:
- To investigate the evolutionary mechanisms driving genome size variation in nematodes, particularly in relation to reproductive modes.
- To test existing hypotheses regarding genome shrinkage, transposable element dynamics, and their role in androdioecious species.
- To identify genetic factors and evolutionary processes underlying genome size differences between dioecious and androdioecious nematodes.
Main Methods:
- Comparative genomic analysis of multiple nematode species, including Caenorhabditis and Pristionchus.
- Phylogenetic analysis to infer evolutionary history and identify patterns of genome size change.
- Quantification and analysis of transposable element abundance and distribution.
- Identification of structural mutations, gene duplications, and insertions across evolutionary distances.
Main Results:
- Genome size evolution showed phylogenetic inertia, with increases observed in some dioecious species, refuting the genome shrinkage hypothesis.
- Transposable elements, except for the Mutator DNA transposon, did not significantly explain genome size variation.
- Caenorhabditis genomes evolved via frequent small structural mutations, including gene-associated duplications and insertions.
- Seventy-one protein families, including those involved in sensory systems and immune responses, showed parallel decreases in androdioecious species.
Conclusions:
- Reproductive mode acts as a significant mediator of genome evolution in Caenorhabditis nematodes.
- Genome evolution is characterized by frequent small rearrangements, with reproductive strategy influencing the fate of specific genes and protein families.
- The study challenges previous hypotheses and highlights the complex interplay between reproduction, mutation, and genome size evolution in nematodes.
Related Concept Videos
03:21Genome Size and the Evolution of New Genes
8.1K
While every living organism has a genome of some kind (be it RNA, or DNA), there is considerable variation in the sizes of these blueprints. One major factor that impacts genome size is whether the organism is prokaryotic or eukaryotic. In prokaryotes, the genome contains little to no non-coding sequence, such that genes are tightly clustered in groups or operons sequentially along the chromosome. Conversely, the genes in eukaryotes are punctuated by long stretches of non-coding sequence.
8.1K
02:37Gene Duplication and Divergence
6.2K
The seminal work of Ohno in 1970 popularized the idea of gene duplication and divergence. DNA sequence comparison studies reveal that a large portion of the genes in bacteria, archaebacteria, and eukaryotes was generated by gene duplication and divergence, indicating its critical role in evolution.
The duplicated copies of the gene are called Paralogs. Paralogs with similar sequences and functions form a gene family. Across several species, a large number of gene families are...
The duplicated copies of the gene are called Paralogs. Paralogs with similar sequences and functions form a gene family. Across several species, a large number of gene families are...
6.2K