Low Mutation Rate and Atypical Mutation Spectrum in Prasinoderma coloniale: Insights From an Early Diverging Green...

Area of Science:

• Evolutionary Biology
• Genetics
• Molecular Biology

Background:

• Mutations drive genetic diversity and adaptation.
• Spontaneous mutation rate (µ) is key to species' adaptive potential.
• Prasinoderma coloniale, an Archaeplastida phytoplankton, has high GC content (69.8%).

Purpose of the Study:

• Estimate mutation rate and spectrum in P. coloniale.
• Investigate the role of cytosine methylation in mutation patterns.
• Understand the evolutionary implications of P. coloniale's unique genomic features.

Main Methods:

• Mutation accumulation experiment in P. coloniale.
• Quantification of single nucleotide mutation rate (µSNM) and insertion-deletion mutation rate (µID).
• Analysis of cytosine methylation levels and its correlation with mutation rates.

Main Results:

• P. coloniale exhibits a very low total mutation rate (µ = 2.00 × 10⁻¹⁰).
• Insertion-deletion mutation rate (µID = 3.40 × 10⁻¹¹) is lower than single nucleotide mutation rate (µSNM = 1.62 × 10⁻¹⁰).
• No AT-bias observed, despite high cytosine methylation (14% 5mC, 25% 5mCG), contradicting expectations.

Conclusions:

• P. coloniale combines a GC-rich genome with a low mutation rate and atypical spectrum.
• Cytosine methylation in P. coloniale does not increase mutation rates.
• The ancestral green lineage may not have had the universal AT-bias.