A weak effect of background selection on trinucleotide microsatellites in maize

Area of Science:

• Genetics
• Evolutionary Biology
• Genomics

Background:

• Artificial selection during maize domestication is believed to primarily involve positive selection, with minimal impact on neutral genetic diversity due to rapid linkage disequilibrium breakdown.
• The extent to which indirect selection has shaped neutral diversity across the maize genome during domestication is not fully understood.

Purpose of the Study:

• To investigate the relationship between local recombination rates and neutral polymorphism in maize and its wild ancestor, teosinte.
• To quantify genetic diversity using parameters sensitive to indirect selection and mutation.

Main Methods:

• Utilized both DNA sequence and microsatellite data from maize and teosinte.
• Estimated three key parameters to measure genetic diversity and infer the effects of selection and mutation.

Main Results:

• Found no consistent genome-wide correlation between genetic diversity and recombination rates in maize.
• Observed a weak positive correlation between heterozygosity and recombination for specific microsatellites within genes, deviating from the stepwise mutation model.
• This correlation was not observed for nucleotide diversity, suggesting stronger purifying selection near these microsatellites.

Conclusions:

• Indirect selection appears to have had a limited genome-wide effect on neutral diversity in maize.
• Background selection may play a role in shaping diversity at specific microsatellite loci within genes.
• Purifying selection might be more potent at certain microsatellite regions compared to nucleotide mutations.