Keeping it complicated: Mitochondrial genome plasticity across diplonemids

Area of Science:

• Genomics
• Evolutionary Biology
• Molecular Biology

Background:

• Chromosome rearrangements drive genome evolution, impacting speciation, development, and disease.
• The flagellate Diplonema papillatum exhibits extensive mitochondrial genome fragmentation and multipartite organization.

Purpose of the Study:

• To investigate the prevalence and nature of mitochondrial genome rearrangements and plasticity within the Diplonema/Rhynchopus clade.
• To understand the evolutionary implications of extensive gene fragmentation and RNA processing in diplonemids.

Main Methods:

• Analysis of mitochondrial genomes and transcriptomes from four species within the Diplonema/Rhynchopus clade.
• Comparative genomics to identify conserved gene breakpoints and variable chromosome structures.

Main Results:

• Gene breakpoints are largely conserved (~80 gene pieces), but chromosome number varies significantly (up to twofold difference).
• Individual chromosomes can aggregate up to eight unrelated gene fragments.
• Substantial overlap exists between internal protein-coding gene pieces.
• Post-transcriptional RNA editing patterns vary, suggesting a compensatory mechanism for sequence evolution and genetic information loss.

Conclusions:

• The Diplonema/Rhynchopus clade displays remarkable genomic plasticity in mitochondrial DNA organization.
• Variations in chromosome number and RNA editing patterns highlight adaptive strategies in response to rapid sequence evolution and chromosome segregation challenges.