Recombination, Truncation and Horizontal Transfer Shape the Diversity of Wolbachia-induced Cytoplasmic...

Area of Science:

• Microbiology
• Genetics
• Evolutionary Biology

Background:

• Wolbachia bacteria induce reproductive manipulations, most commonly cytoplasmic incompatibility (CI).
• CI reduces embryo viability in crosses between infected males and uninfected females.
• Culex pipiens mosquitoes exhibit complex CI patterns linked to Wolbachia wPip's cidA and cidB genes.

Purpose of the Study:

• To investigate if cid gene polymorphism alone explains the diverse CI crossing patterns in Culex pipiens.
• To sequence complete cid repertoires from worldwide wPip strains.
• To correlate cid gene variants with observed CI patterns.

Main Methods:

• Sequencing of complete cid repertoires from 45 wPip strains using a novel full-gene acquisition method.
• Analysis of cid gene diversity, recombination, and horizontal transfer events.
• Correlation of specific cidB variants with cytoplasmic incompatibility (CI) patterns.

Main Results:

• Extensive diversity in cid genes arises from recombination and horizontal transfers.
• Polymorphism in cidB outside interaction regions strongly correlates with CI patterns.
• In most wPip genomes, only one cidB variant is full-length; truncated variants lack crucial domains.
• The sole full-length cidB variant appears to determine CI patterns, regardless of truncated variants.

Conclusions:

• The identity of the single full-length cidB variant is the primary determinant of CI patterns in Culex pipiens.
• Truncated cidB variants show reduced stability and toxicity, potentially affecting CI induction.
• Understanding cid gene polymorphism provides insight into the evolution of reproductive manipulation by Wolbachia.