required to maintain repression2 is a novel protein that facilitates locus-specific paramutation in maize

Area of Science:

• Epigenetics
• Plant Molecular Biology
• Genetics

Background:

• Paramutation involves meiotically heritable epigenetic changes in gene regulation.
• Trans-homolog interactions facilitate paramutation, but the underlying mechanisms are poorly understood.
• Maize paramutation studies suggest roles for small RNAs and RNA-directed DNA methylation (RdDM).

Purpose of the Study:

• To identify novel proteins involved in paramutation in maize.
• To investigate the role of small RNAs in mediating paramutation.
• To determine if maize paramutation mechanisms are distinct from RdDM.

Main Methods:

• Genetic screens in maize (Zea mays) to identify mutations affecting paramutation.
• Analysis of 24-nucleotide RNA accumulation.
• Investigation of DNA methylation patterns.
• Comparative genetic analysis at different loci (Pl1-Rhoades and red1).

Main Results:

• A novel protein, required to maintain repression2 (RMR2), was identified and is crucial for paramutation at the purple plant1 (Pl1) locus.
• RMR2 is necessary for the accumulation of 24-nucleotide RNAs and maintains a distinct 5-methylcytosine pattern.
• RMR2 is not required for paramutation at the red1 locus, indicating locus-specific mechanisms.
• RMR2 represents a new plant-specific protein clade.

Conclusions:

• RMR2 plays a critical role in a specific paramutation pathway at the Pl1 locus in maize.
• The findings distinguish paramutation mechanisms operating at different haplotypes.
• The RMR2 protein clade offers new insights into the diversity of epigenomic control in plants.