Evolutionary Diversification and Functions of the Candidate Male Killing Gene wmk

Area of Science:

• Evolutionary biology
• Microbial genetics
• Genomics

Background:

• Symbiont-mediated male killing (MK) is a reproductive strategy where microbes eliminate male offspring.
• The wmk gene from Wolbachia prophage WO in Drosophila melanogaster causes the MK phenotype.
• The evolutionary and functional diversity of wmk genes across Wolbachia remains under-investigated.

Purpose of the Study:

• To systematically investigate the evolution and function of wmk homologs across diverse Wolbachia.
• To analyze wmk gene diversity, phylogenetic clusters, and genomic organization in relation to host arthropods and reproductive parasitism.
• To understand the genetic basis of wmk-induced male lethality in Drosophila melanogaster.

Main Methods:

• Bioinformatic analysis of 32 Wolbachia genomes from the NCBI database.
• Phylogenetic analysis to identify wmk gene clusters (Types I-V).
• Transgenic expression of wmk gene types in Drosophila melanogaster to assess lethality and reproductive effects.

Main Results:

• Identification of at least five distinct wmk phylogenetic clusters (Types I-V), often in multigenic arrangements.
• Higher wmk gene number and diversity observed in Lepidoptera strains compared to Drosophila strains.
• Transgenic expression revealed male-biased lethality with Type I wmk, and reduced offspring number with combined Type I and III expression in D. melanogaster.
• Low expression of wmk genes in D. melanogaster relative to cifA and cifB genes.

Conclusions:

• The genetic basis of wmk-induced lethality is complex, influenced by gene copy number, expression levels, wmk types, and host background.
• Wolbachia wmk genes exhibit significant phylogenetic and genomic diversity, correlating with different evolutionary trajectories of the male-killing phenotype.
• Further research into wmk gene evolution and function is crucial for understanding reproductive parasitism in arthropods.