Accelerated evolutionary rate may be responsible for the emergence of lineage-specific genes in ascomycota
J Mol Evol. 2006 Jul;63(1):1-11. Epub 2006 Jun 3.
Accelerated evolutionary rate may be responsible for the
emergence of lineage-specific genes in ascomycota.
Cai JJ, Woo PC, Lau SK, Smith DK, Yuen KY.
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,
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.
PMID: 16755356 [PubMed - indexed for MEDLINE]
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