Evidence that DNA repair genes, a family of tumor suppressor genes, are associated with evolution rate and size of genomes

Consistent with the theme of “evolution” that is often discussed in these GEITP pages, “adaptive radiation” is a well-known phenomenon in evolutionary biology — in which a taxon (a taxonomic group of any rank, such as a class, family, order, genus, species) is divided into multiple species, which then had adapted to various environments, over a short evolutionary time. Although this phenomenon has been popularized mostly in island studies [e.g. Darwin’s finches, Hawaiian fruit flies (Drosophila)] — other major adaptive radiations have occurred [e.g. cichlids (a tropical freshwater fish of the family Cichlidae), bats, and cetaceans (a marine mammal of the order Cetacea: whale, dolphin, or porpoise)]. It is very likely that common evolutionary and molecular processes are seen in all taxa that have experienced adaptive radiation; however, no such common molecular pathways have been identified to date.

Authors [see attached article] considered living fossils and adaptive radiation as two very different evolutionary strategies: slow evolutionary rate versus rapid evolutionary rate, respectively. Living fossils are characterized by morphological stasis, low (taxonomic) diversity, and rareness; the apparent absence of their morphological stability and low diversification — suggest highly effective adaptations that decrease the need for phenotypic change, regardless of environmental or genetic changes. Living fossils are frequently referred to as examples of evolutionary success and evolutionary stasis (evolutionary stasis is commonly seen in the fossil record).

Classical examples of taxa — considered by most biologists as living fossils — are the crocodilians (crocodile, alligator), coelacanths (large, bony marine fish with a three-lobed tail fin and fleshy pectoral fins; thought to be related to the ancestors of land vertebrates, and known only from fossils — until one was found alive in 1938), and ornithorhynchus (another term for platypus). Similar to the category of adaptive radiation, there are no specific genes that are under selection in living fossil species. Authors [see attached article] attempted to identify any common molecular pathways that contributed to a specific evolutionary process in living fossils vs adaptive radiation species; they were principally interested in genes related to disease — because evolutionary studies may contribute to a better understanding of the function of “disease” genes.

Pathway analysis revealed that DNA repair and cellular response to DNA damage were most important for species that had evolved through adaptive radiation. Nucleotide excision repair and base excision repair were the most significant pathways. In addition, the number of DNA repair genes was found to be linearly related to the genome size and the protein number (proteome) of the 44 animal species analyzed (P <1.0 × 10-4). Authors also showed evidence that cancer-related genes play a special role in adaptive radiation species. Note this study is a completely “dry-lab” bioinformatics analysis, relying on existing databases (i.e. genomes already sequenced for all these 44 species). 😊 DwN Hum Genomics June 2019; 13: 26

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