Regulation of mutator activities in maize

Area of Science:

• Genetics
• Molecular Biology
• Plant Science

Background:

• The Mutator (Mu) transposable element family in maize is crucial for genetic variation.
• Understanding the regulation of Mu elements is key to studying genome stability and evolution.

Purpose of the Study:

• To investigate the relationship between DNA modification and the activity of Mu transposable elements in maize.
• To characterize the bz2-mu1 mutable allele and the structure of the Bz2 locus.
• To explore the reactivation of inactive Mutator lines.

Main Methods:

• Cloning of the bz2-mu1 mutable allele using transposon tagging.
• DNA sequencing of the allele and Mu element insertion.
• Northern and Southern blot analyses for differential hybridization.
• Analysis of DNA modification levels using CsCl density gradients and gene-specific probes.
• Gamma-irradiation to induce reactivation of inactive Mutator lines.

Main Results:

• The bz2-mu1 allele contains a 1.4-kb Mu element, and its sequence provides insights into the Bz2 locus structure.
• Active Mutator lines show hypomethylation of Mu elements compared to other maize DNA.
• Inactive Mutator lines exhibit Mu element methylation levels similar to the overall genome.
• Gamma-irradiation reactivated inactive lines, restoring the spotted kernel phenotype and reducing Mu element DNA modification.

Conclusions:

• DNA modification plays a critical role in regulating the activity and somatic instability of Mutator transposable elements in maize.
• Hypomethylation is associated with active Mutator elements, while increased methylation correlates with inactivation.
• Inactive Mutator lines can be epigenetically reprogrammed, demonstrating the dynamic nature of transposable element regulation.