Accelerated evolutionary rate may be responsible for the emergence of lineage-specific genes in ascomycota.

Full Abstract

The evolutionary origin of "orphan" genes, genes that lack sequence similarity to any known gene, remains a mystery. One suggestion has been that most orphan genes evolve rapidly so that similarity to other genes cannot be traced after a certain evolutionary distance. This can be tested by examining the divergence rates of genes with different degrees of lineage specificity. Here the lineage specificity (LS) of a gene describes the phylogenetic distribution of that gene's orthologues in related species. Highly lineage-specific genes will be distributed in fewer species in a phylogeny. In this study, we have used the complete genomes of seven ascomycotan fungi and two animals to define several levels of LS, such as Eukaryotes-core, Ascomycota-core, Euascomycetes-specific, Hemiascomycetes-specific, Aspergillus-specific, and Saccharomyces-specific. We compare the rates of gene evolution in groups of higher LS to those in groups with lower LS. Molecular evolutionary analyses indicate an increase in nonsynonymous nucleotide substitution rates in genes with higher LS. Several analyses suggest that LS is correlated with the evolutionary rate of the gene. This correlation is stronger than those of a number of other factors that have been proposed as predictors of a gene's evolutionary rate, including the expression level of genes, gene essentiality or dispensability, and the number of protein-protein interactions. The accelerated evolutionary rates of genes with higher LS may reflect the influence of selection and adaptive divergence during the emergence of orphan genes. These analyses suggest that accelerated rates of gene evolution may be responsible for the emergence of apparently orphan genes.

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Author information

Author/s: Cai, James J (JJ); Woo, Patrick C Y (PC); Lau, Susanna K P (SK); Smith, David K (DK); Yuen, Kwok-Yung (KY);

Affiliation: Department of Microbiology, Faculty of Medicine, University of Hong Kong, University Pathology Building, Queen Mary Hospital, 102 Pokfulam Road, Hong Kong SAR, China. jamescai(-atsign-)hku.hk

Journal and publication information

Publication Type: Comparative Study; Journal Article; Research Support, Non-U.S. Gov't

Journal: Journal of molecular evolution (J Mol Evol), published in Germany. (Language: eng)

Reference: 2006-Jul; vol 63 (issue 1) : pp 1-11

Dates: Created 2006/06/30; Completed 2006/09/27; Revised 2006/11/15;

PMID: 16755356, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Ascomycota - genetics
Aspergillus fumigatus - classification; genetics
Cell Lineage - genetics
Databases, Genetic
Evolution, Molecular
Genes, Fungal
Genetic Drift

Genetic Drift
Genetic Speciation
Linear Models
Models, Theoretical
Phylogeny
Saccharomyces cerevisiae - classification; genetics
Species Specificity

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