Transposon-induced inversions activate gene expression in the maize pericarp

Area of Science:

• Plant genetics
• Molecular biology
• Genomics

Background:

• Chromosomal inversions significantly impact gene function, expression, and recombination, with agricultural relevance.
• In maize, the p1 and p2 genes control floral pigmentation; a specific line (p1-wwB54) exhibits white kernels due to a null p1 gene and restricted p2 expression.

Purpose of the Study:

• To investigate the molecular basis and functional consequences of six chromosomal inversions in maize.
• To understand how these inversions, mediated by transposable elements, affect gene expression and kernel pigmentation.

Main Methods:

• Screening maize lines for red pericarp kernels to identify relevant genetic alterations.
• Analyzing the molecular structure of identified inversions.
• Investigating the impact of inversions on gene promoter-enhancer interactions and gene expression.

Main Results:

• Identified six recurrent chromosomal inversions in the p1-p2 gene region, caused by Ac and fractured Ac (fAc) transposable elements.
• Observed that these inversions reposition the p2 gene promoter near a p1 gene enhancer.
• Demonstrated that this repositioning leads to ectopic expression of p2 in the kernel pericarp, restoring red pigmentation.

Conclusions:

• The study reports the first instance of multiple recurrent inversions inducing ectopic gene expression via promoter-enhancer interaction changes in a eukaryote.
• These findings provide novel insights into the mechanisms of gene regulation and the evolutionary potential of chromosomal rearrangements.