Centromere Plasticity With Evolutionary Conservation and Divergence Uncovered by Wheat 10+ Genomes

Area of Science:

• Plant genetics and epigenetics
• Genomic stability and evolution
• Chromosomal structure and function

Background:

• Centromeres (CEN) are vital for genomic stability, yet their repetitive DNA sequences evolve rapidly.
• Understanding how variable centromeric sequences maintain function is a key challenge in eukaryotes.
• Wheat centromeres are large, complex, and exhibit significant sequence and epigenetic variation.

Purpose of the Study:

• To investigate the genetics and epigenetics of centromeres in diverse wheat lines.
• To understand how centromeric sequences and epigenetic modifications ensure centromere function and stability.
• To explore the role of CENH3 nucleosome structure in centromere identity and adaptation.

Main Methods:

• Analysis of centromeric DNA sequences and their association with CENH3 in wheat lines.
• Examination of CENH3 nucleosome positioning and DNA wrapping.
• Identification of non-B DNA forms associated with centromeric nucleosomes.

Main Results:

• Wheat centromeres display high sequence, positioning, and epigenetic variation.
• Cereba retrotransposon elements are the primary CENH3-associated repeats, showing homogenization.
• Less-associated repeats diverge, suggesting selection for specific functional core CEN sequences.
• CENH3 nucleosomes exhibit looser DNA wrapping at termini and specific non-B DNA associations.
• Strict CENH3 positioning and DNA features contribute to centromere identity.

Conclusions:

• Multiple mechanisms adapt CENH3 nucleosomes to stabilize centromeres in wheat.
• Epigenetic plasticity of centromere chromatin is crucial for maintaining function and genome stability.
• Centromere robustness in wheat lines reflects adaptation through breeding selections.