Megabase-scale inversion polymorphism in the wild ancestor of maize.

Area of Science:

• Population genetics
• Genomics
• Evolutionary biology

Background:

• Chromosomal inversions are hypothesized to facilitate local adaptation by suppressing recombination.
• Characterization of inversions in population genomic data remains limited.

Purpose of the Study:

• To identify and characterize chromosomal inversions in Zea mays using population genomic data.
• To investigate the evolutionary history and adaptive significance of a putatively identified inversion.

Main Methods:

• Single-nucleotide polymorphism (SNP) genotyping across a large panel of Zea mays.
• Comparative genomic analysis with related taxa (Zea and Tripsacum).
• Cytological screening for inversion heterozygotes.

Main Results:

• Identification of a large (~50 Mb) paracentric inversion on chromosome 1 of Zea mays, encompassing over 700 genes.
• The inverted allele is present in wild subspecies (parviglumis, mexicana) but absent in domesticated maize.
• Evidence suggests the inversion is ancient, widespread, and under adaptive evolution, showing an altitudinal cline and association with environmental variables.

Conclusions:

• The identified inversion is a significant feature in the evolution of wild maize subspecies.
• The inversion likely plays a role in local adaptation and is a key differentiator between wild and domesticated maize.
• Low evidence of inversion loops suggests minimal fitness costs for heterozygotes.