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Predictors of Protein Evolution in the drosophilid Immune System
Pankaj Dhakad1, Darren J Obbard1
1Institute of Ecology and Evolution, University of Edinburgh, Edinburgh, UK.
Genome Biology and Evolution
|February 16, 2026
Summary
Immune genes evolve faster at the protein sequence level but turn over slower than other genes. This immune diversification in Drosophilidae is shaped by structural constraints, functional roles, and pathogen pressures.
Area of Science:
- Evolutionary biology
- Immunology
- Genomics
Background:
- Immune gene evolution is complex, influenced by various selective pressures.
- The roles of gene traits, functional specialization, and pathway context are not fully understood.
Purpose of the Study:
- To quantify differences in evolutionary rates (dN/dS, positive selection, gene turnover) between immune and non-immune genes.
- To assess the impact of gene-level traits and pathway context on immune gene evolution.
Main Methods:
- Meta-analytic mixed model approach.
- Analysis of protein sequence divergence (dN/dS), positive selection, and gene turnover rate (λ).
- Inclusion of gene length, expression, interactions, and relative solvent accessibility (RSA) as covariates.
Main Results:
- Immune genes show faster protein sequence evolution (higher dN/dS) but lower gene turnover rates than non-immune genes.
- Accelerated evolution observed in effectors, receptors, and antiviral genes, particularly in cGAS-STING and Toll pathways.
- Positive selection is elevated in immune genes, especially effectors, indicating adaptive diversification.
Conclusions:
- Immune gene evolution is shaped by a combination of structural constraints, functional roles, and pathogen pressures.
- Diversification of immune responses in Drosophilidae involves multiple, partly independent evolutionary processes.
- Specific immune pathways and gene types exhibit distinct evolutionary dynamics.
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