Submitted to: Proceedings of the National Academy of Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2005
Publication Date: 3/21/2005
Citation: Rooney, A.P., Ward, T.J. 2005. Evolution of a large Ribosomal RNA multigene family in filamentous fungi: Birth and death of concerted evolution paradigm. Proceedings of the National Academy of Sciences. 102(14):5084-5089. Interpretive Summary: This paper describes a study on the evolutionary genomics of the 5S ribosomal RNA gene family in certain plant pathogenic fungi. We found that the 5S genes appear to copy themselves multiple times and subsequently insert into various areas of the genome. Furthermore, we found that the genes undergo an unusual pattern of divergence called "birth-and-death evolution". This is the first case in which these patterns have been described for a large ribosomal RNA multigene family. This study furthers our understanding of how the genomes of plant pathogenic fungi diversify and evolve, which will aid efforts focused on the long-term monitoring of these organisms.
Technical Abstract: The 5S gene is the smallest of the four nuclear ribosomal RNA (rRNA) genes in eukaryotes. In some species the gene is part of the regular rRNA tandem array, while in others the gene is dispersed. The 5S rRNA genes of filamentous fungi form a large multigene family of 50 to 100 copies. During the course of our studies on the genomic evolution of filamentous fungi, we found that these genes display varying degrees of divergence from one another, suggesting that they do not evolve in a concerted manner. This pattern is quite unusual because nuclear rRNA genes represent a paradigm of concerted evolution. The purpose of this study was to characterize the patterns of multigene family evolution and evolutionary genomics of 5S rRNA genes in the genomes of representative filamentous fungi. Our studies show that the genes undergo birth-and-death evolution under strong purifying selection. Furthermore, the rate of gene turnover appears to be quite high in these genomes. Because the 5S genes in these species are dispersed across the genome, our findings indicate that the mechanisms controlling the multiplication and movement of 5S genes across the genome are highly dynamic. This is the first case in which these patterns have been described for a large rRNA multigene family. Furthermore it appears that a process resembling retroposition controls 5S rRNA gene amplification, dispersal and integration in the genomes of filamentous fungi.