The differential loading of two barley CENH3 variants into distinct centromeric substructures is cell type- and...

Area of Science:

• * Molecular Biology
• * Genetics
• * Cell Biology

Background:

• * Centromeres are crucial for chromosome segregation during cell division.
• * Histone H3 variants, like CENH3, are key components of centromeric chromatin.
• * Diploid barley (Hordeum vulgare) possesses two distinct CENH3 variants (α and β).

Purpose of the Study:

• * To investigate the spatial organization of α and β CENH3 variants within barley centromeres.
• * To determine if CENH3 variants exhibit tissue-specific localization or functional differentiation.
• * To elucidate the structural basis of centromeric chromatin organization in barley.

Main Methods:

• * Super-resolution microscopy was employed to visualize centromeric chromatin organization.
• * Antibody staining was used to differentiate and localize α and β CENH3 variants.
• * Artificially extended chromatin fibers were analyzed to understand subdomain formation.

Main Results:

• * Both α and β CENH3 variants form distinct, intermingled subdomains within interphase, mitotic, and meiotic centromeres.
• * These subdomains are structurally composed of polynucleosome clusters.
• * CENH3 variant composition and transcription patterns differ across tissues (e.g., young embryos vs. root meristems).
• * In root cells, βCENH3 was often dispersed within the nucleoplasm.
• * No preferential arrangement of CENH3 variants relative to spindle poles was observed in metaphase cells.

Conclusions:

• * Barley centromeres utilize a specific loading and arrangement mechanism for α and β CENH3 variants into intermingling subdomains.
• * Tissue-specific expression and localization suggest potential specialized functions for CENH3 variants.
• * Despite observed differences, both CENH3 homologs appear to fulfill the same essential function in metaphase centromeres.