Large-scale search for genes on which positive selection may operate

Area of Science:

• Evolutionary genetics
• Molecular evolution
• Bioinformatics

Background:

• Positive selection drives adaptive evolution by favoring beneficial mutations.
• Identifying genes under positive selection is crucial for understanding evolutionary adaptation.
• Comparative genomics offers a powerful approach to detect signatures of selection.

Purpose of the Study:

• To systematically search for candidate genes that have undergone positive selection.
• To estimate the proportion of genes subjected to positive selection in available sequence data.
• To investigate the functional categories of genes showing signs of positive selection.

Main Methods:

• Conducted a systematic search using DNA sequence databases (DDBJ, EMBL, GenBank).
• Analyzed 3,595 groups of homologous gene sequences.
• Applied the principle that positive selection is indicated by a higher ratio of nonsynonymous to synonymous substitutions.

Main Results:

• Identified 17 gene groups as candidates for positive selection.
• These positively selected genes represent approximately 0.5% of the analyzed gene groups.
• Notably, 9 out of the 17 candidate gene groups encode surface antigens of parasites or viruses.

Conclusions:

• Positive selection acts on a small subset of genes within the genome.
• Surface antigens of pathogens are frequently targeted by positive selection, suggesting rapid evolution in host-pathogen interactions.
• The findings provide insights into the evolutionary dynamics of genes involved in host defense and pathogen evasion.