Journal
GENOME BIOLOGY AND EVOLUTION
Volume 2, Issue -, Pages 180-189Publisher
OXFORD UNIV PRESS
DOI: 10.1093/gbe/evq009
Keywords
birth-and-death evolution; gene duplication; gene regulation; multigene family; noncoding RNA; substitution rate
Categories
Funding
- National Institutes of Health [GM020293]
- Japan Society for the Promotion of Science
- NATIONAL INSTITUTE OF GENERAL MEDICAL SCIENCES [R01GM020293] Funding Source: NIH RePORTER
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MicroRNAs (miRs) regulate gene expression at the posttranscriptional level. To obtain some insights into the origins and evolutionary patterns of miR genes, we have identified miR genes in the genomes of 12 Drosophila species by bioinformatics approaches and examined their evolutionary changes. The results showed that the extant and ancestral Drosophila species had more than 100 miR genes and frequent gains and losses of miR genes have occurred during evolution. Although many miR genes appear to have originated from random hairpin structures in intronic or intergenic regions, duplication of miR genes has also contributed to the generation of new miR genes. Estimating the rate of nucleotide substitution of miR genes, we have found that newly arisen miR genes have a substitution rate similar to that of synonymous nucleotide sites in protein-coding genes and evolve almost neutrally. This suggests that most new miR genes have not acquired any important function and would become inactive. By contrast, old miR genes show a substitution rate much lower than the synonymous rate. Moreover, paired and unpaired nucleotide sites of miR genes tend to remain unchanged during evolution. Therefore, once miR genes acquired their functions, they appear to have evolved very slowly, maintaining essentially the same structures for a long time.
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