An Alternative Self-Splicing Intron Lifecycle Revealed by Dynamic Intron Turnover in Epichloë Endophyte Mitochondrial...

Area of Science:

• Genetics
• Evolutionary Biology
• Mycology

Background:

• Self-splicing group I and II introns are mobile genetic elements known for their
• homing
• super-Mendelian inheritance.

Purpose of the Study:

• Investigate the evolutionary dynamics of self-splicing introns in Epichloë mitochondrial genomes.
• Determine if Epichloë introns follow the established intron lifecycle model.

Main Methods:

• Analysis of intron presence-absence polymorphism in Epichloë species.
• Inferred evolutionary events including vertical inheritance, invasion, and loss.

Main Results:

• Self-splicing introns are common in Epichloë mitochondrial genomes but show significant presence-absence polymorphism.
• Evidence suggests multiple invasion and loss events, alongside vertical inheritance.
• Introns appear to be lost rapidly after fixation, with little evidence of extensive degradation.

Conclusions:

• Epichloë self-splicing introns possess a distinct lifecycle characterized by rapid loss.
• Homing suppressors likely play a role in intron dynamics, alongside rapid loss.
• Self-splicing intron evolution is more diverse than previously understood.