Heteroplasmy Is Rare in Plant Mitochondria Compared with Plastids despite Similar Mutation Rates

Area of Science:

• Plant cell biology
• Organelle genetics
• Evolutionary biology

Background:

• Plant cells contain plastids and mitochondria, each with unique genetic material.
• These organelles differ in genome copy number, organization, and segregation, affecting allele dynamics.
• The impact of these differences on neutral allele fixation or loss remains unclear.

Purpose of the Study:

• To investigate the factors determining allele segregation and fixation in plant organelles.
• To compare the dynamics of mitochondrial and plastid alleles within plant cells.
• To understand the evolutionary implications of organelle allele fixation differences.

Main Methods:

• Analysis of genetic variants in Zostera marina populations.
• Simulation of organelle allele dynamics.
• Comparative analysis of mutation rates and allele persistence.

Main Results:

• Mitochondria and plastids exhibit similar mutation rates.
• Plastid alleles remain heteroplasmic for significantly longer periods than mitochondrial alleles.
• Cell population bottlenecks and meristem stratification influence mitochondrial allele dynamics.
• A potential active plastid partitioning mechanism may explain prolonged plastid allele dynamics.

Conclusions:

• Organelle population genetics reveal distinct segregation and fixation mechanisms for mitochondria and plastids.
• Differences in organelle allele dynamics can influence adaptation processes.
• These findings are crucial for understanding long-term evolution and molecular dating.