Quantifying the coevolutionary potential of multistep immune defenses

Area of Science:

• Evolutionary biology
• Immunology
• Genetics

Background:

• Coevolutionary models traditionally simplify host-parasite interactions to single molecular recognition events.
• Accumulating immunological data highlight the importance of multi-step infection processes in determining host-parasite interaction outcomes.
• Innate immunity in plants and animals involves sequential recognition and effector steps, creating a molecular arms race.

Purpose of the Study:

• To investigate the impact of multi-step infection processes on coevolutionary dynamics.
• To analyze the genetic consequences of complex host-parasite interactions using a genetically explicit model.

Main Methods:

• Development and analysis of a genetically explicit coevolutionary model.
• Examination of polymorphism levels at recognition and effector loci.
• Quantification of host-genotype by parasite-genotype (Gh × Gp) interactions.

Main Results:

• Recognition loci exhibit significantly greater polymorphism than effector loci.
• Host-genotype by parasite-genotype interactions are more pronounced at the recognition step.
• The recognition step contributes more substantially to local adaptation than the effector step.

Conclusions:

• Local adaptation is more probable when fitness is linked to recognition processes rather than downstream effectors.
• Effector loci, despite their functional importance, are less likely to be sources of the genetic variation driving coevolution.
• Recognition loci represent promising candidates for genomic hotspots of coevolution.