Distinct regulatory pathways contribute to dynamic CHH methylation patterns in transposable elements throughout...

Area of Science:

• Plant Epigenetics
• Developmental Biology
• Genomics

Background:

• Cytosine methylation at the CHH sequence context (mCHH) increases during plant embryogenesis, suggesting conserved epigenetic regulation.
• While increased mCHH is linked to transposable element silencing, the precise epigenetic pathways remain unclear.
• In Arabidopsis, mCHH is controlled by both small RNA-dependent DNA methylation (RdDM) and RNA-independent Chromomethylase 2 (CMT2) pathways.

Purpose of the Study:

• To investigate the epigenetic pathways regulating mCHH dynamics during Arabidopsis embryogenesis.
• To classify mCHH regions based on their dependency on RdDM and CMT2 pathways.
• To understand how transposable element characteristics influence epigenetic targeting during development.

Main Methods:

• Conducted DNA methylome profiling across five stages of Arabidopsis embryogenesis.
• Classified mCHH regions based on their differential dependency on methylation pathways (RdDM and CMT2).
• Analyzed the relationship between transposon features (length, location, cytosine frequency) and mCHH regulation.

Main Results:

• Observed a gradual increase in mCHH during embryogenesis, correlating with expanded small RNA expression and regional mCHH spreading.
• Identified distinct mCHH dynamics for different target regions, influenced by transposon characteristics.
• Found that short, heterochromatic TEs with lower mCHG levels switch from CMT2 to RdDM regulation during embryogenesis.

Conclusions:

• The interplay between transposon features and mCHH machinery modulates epigenetic dynamics during plant embryogenesis.
• Developmental regulation of mCHH involves a complex interplay between RdDM and CMT2 pathways, influenced by TE properties.
• This study provides insights into the precise epigenetic mechanisms controlling transposon silencing during embryonic development.