Haplotype structure and expression divergence at the Drosophila cellular immune gene eater

Area of Science:

• Evolutionary biology
• Immunology
• Genetics

Background:

• The protein Eater is crucial for microbial recognition and phagocytosis in Drosophila melanogaster.
• Understanding the evolutionary pressures on immune genes is vital for comprehending host-pathogen dynamics.

Purpose of the Study:

• To investigate the evolutionary adaptation of the eater gene in Drosophila melanogaster.
• To identify the genetic basis of local adaptation in North American populations.

Main Methods:

• Sequencing of multiple eater gene alleles from African and North American D. melanogaster populations.
• Analysis of genetic signatures of selection, including selective sweeps and haplotype structures.
• Gene expression level analysis associated with different haplotypes.

Main Results:

• Signatures of a partial selective sweep were detected in the North American eater gene, localized to the second intron.
• A putatively selected haplotype in North America showed significantly higher eater gene expression.
• No evidence of elevated positive selection on pathogen-interacting NIM repeats within the eater gene was found.

Conclusions:

• Local adaptation of the eater gene in North America is likely driven by changes in gene regulation rather than protein structure.
• Gene expression evolution is a key factor in the adaptive evolution of pathogen recognition molecules.
• This study provides an example of how gene regulation can be a target of selection in immune system evolution.