The genome-wide dynamics of purging during selfing in maize

Area of Science:

• Plant Genetics
• Evolutionary Biology
• Genomics

Background:

• Self-fertilization (selfing) is a key reproductive strategy in plants, influencing genetic diversity.
• Selfing can expose deleterious alleles, potentially causing inbreeding depression, but selection can purge these variants.

Purpose of the Study:

• To investigate the dynamics of purging deleterious variants during self-fertilization in maize.
• To understand how recombination affects the efficiency of purging.
• To examine genome size changes associated with selfing.

Main Methods:

• Eleven maize lines were subjected to six generations of self-fertilization.
• Single nucleotide polymorphisms (SNPs) and heterozygosity were analyzed to track variant loss.
• Genome size and transposable element content were measured.

Main Results:

• Heterozygous deleterious single nucleotide polymorphisms (SNPs) were preferentially lost during selfing.
• Purging was faster in high-recombination regions, indicating selection efficacy is enhanced by recombination.
• Overall heterozygosity reduction was slower than expected (35-40% per generation), suggesting associative overdominance.
• Three maize lines showed significant genome size reduction due to transposable element purging, losing up to 398 Mb.

Conclusions:

• Selfing effectively purges deleterious alleles in maize, with recombination playing a crucial role.
• Associative overdominance may slow the rate of heterozygosity loss during selfing.
• Significant genome reduction can occur through transposable element purging in specific maize lineages under selfing.