Cohesin overexpression linked to programmed B chromosome loss in wheat relative Aegilops speltoides

Researchers have used a chromosome-scale genome assembly of Aegilops speltoides — a wild relative of wheat — to investigate the molecular basis of programmed chromosome elimination, a developmental process in which specific chromosomes are selectively lost from defined cell lineages. The study, posted as a preprint to bioRxiv, focuses on the root-specific elimination of supernumerary B chromosomes, a phenomenon that has been observed across diverse plants and animals but whose mechanistic underpinnings remain largely unresolved.

The team generated a high-quality assembly assigning 398 megabases of sequence to chromosome-scale scaffolds, providing a reference for detailed transcriptomic comparisons between cell types that retain and those that eliminate B chromosomes. They report that programmed loss correlates with overexpression of cohesin — a protein complex central to sister chromatid cohesion and chromosome segregation — along with a set of additional genes encoded by the B chromosomes themselves.

The findings support a model in which B chromosomes may encode or influence the very machinery that governs their own elimination in particular tissues, a form of intragenomic conflict with parallels in other selfish genetic elements. The authors describe the Aegilops speltoides system as a tractable experimental model for dissecting the molecular genetics of chromosome loss more broadly.

This work is a preprint and has not yet completed peer review.