Paternally expressed imprinted genes associate with hybridization barriers in Capsella

Area of Science:

• Plant reproductive biology
• Genetics and genomics
• Evolutionary biology

Background:

• Hybrid seed lethality is a common reproductive barrier in angiosperms, hindering gene flow and impacting plant breeding.
• This lethality often results from endosperm failure due to parental dosage imbalance, influenced by effective ploidy or endosperm balance number (EBN).
• Parent-of-origin effects and imprinted genes are implicated in the molecular basis of EBN.

Purpose of the Study:

• To investigate the relationship between effective ploidy, paternally expressed genes (PEGs), and breeding history in Capsella species.
• To explore the role of transposable elements in driving imprintome divergence and establishing hybridization barriers.

Main Methods:

• Comparative analysis of effective ploidy, PEG number, and expression levels across three Capsella species with varying selfing histories.
• Investigation of the association between PEGs, transposable elements, and DNA methylation patterns (specifically CHH context).

Main Results:

• Effective ploidy in Capsella correlates with PEG number and expression levels.
• PEG number and effective ploidy decrease with increased selfing history (Capsella grandiflora > Capsella rubella > Capsella orientalis).
• PEGs are linked to transposable elements and CHH DNA methylation, suggesting their role in imprintome evolution.

Conclusions:

• Variation in transposable elements influences PEG number and expression, contributing to effective ploidy differences between species.
• These variations play a role in establishing endosperm-based hybridization barriers, particularly in relation to species' breeding systems.