Maize centromeric chromatin scales with changes in genome size.

Area of Science:

• Genetics
• Molecular Biology
• Plant Science

Background:

• Centromeres are essential chromosomal regions, epigenetically defined by the histone variant CENP-A (Centromeric Histone H3/CENH3).
• Centromere size and function are critical for accurate chromosome segregation during cell division.
• Understanding factors regulating centromere size is key to comprehending genome stability.

Purpose of the Study:

• To investigate the relationship between genome size and functional centromere size in maize.
• To determine if centromere size variation is linked to the abundance of the CentC satellite repeat.
• To explore the mechanisms underlying centromere size plasticity.

Main Methods:

• Analysis of 110 centromeric regions across 26 diverse maize genomes.
• Backcrossing experiments to introduce known centromeres into maize lines with larger genomes.
• Assessment of CENP-A (CENH3) binding and centromere size changes.

Main Results:

• A positive correlation was found between maize genome size and functional centromere size.
• Centromere size expansion occurred independently of variations in the major CentC satellite sequence.
• Backcrossing confirmed that centromere size increases in larger genomic contexts, despite CENP-A levels not being the sole limiting factor.

Conclusions:

• Centromere size is a scalable feature of the genome, similar to cell and organelle size.
• Multiple regulatory factors contribute to maintaining a stable centromere size equilibrium.
• Genome size influences functional centromere dimensions, highlighting a novel aspect of genome evolution and stability.