ONSEN shows different transposition activities in RdDM pathway mutants.

Area of Science:

• Plant molecular biology
• Epigenetics
• Genomics

Background:

• Transposable elements (TEs) are mobile genetic sequences.
• Epigenetic mechanisms, particularly DNA methylation, regulate TEs.
• RNA-directed DNA methylation (RdDM) is crucial for TE silencing in plants.

Purpose of the Study:

• To investigate the transposition activity of the heat-responsive retrotransposon ONSEN in Arabidopsis thaliana.
• To determine the role of the RNA-directed DNA methylation (RdDM) pathway in regulating ONSEN transposition under heat stress.
• To analyze the impact of heat stress on chromatin structure in relation to RdDM and ONSEN activity.

Main Methods:

• Analysis of ONSEN retrotransposon transposition in Arabidopsis thaliana mutants.
• Assessment of transgenerational transposition events under heat stress conditions.
• Examination of DNA methylation patterns and chromatin decondensation in wild-type and RdDM pathway-deficient mutants.
• Quantification of extrachromosomal ONSEN copies.

Main Results:

• Transgenerational transposition of ONSEN was observed in RdDM pathway-deficient mutants upon heat stress.
• ON SEN transposition frequency varied depending on the specific RdDM pathway component affected.
• Heat stress caused dispersion of constitutive heterochromatin, with greater decondensation in RdDM mutants.
• No association was found between ONSEN transposition frequency and extrachromosomal ONSEN copy number.

Conclusions:

• The RNA-directed DNA methylation (RdDM) pathway plays a significant role in suppressing ONSEN retrotransposon activity, especially under heat stress.
• Disruption of RdDM leads to increased ONSEN transposition and chromatin decondensation in response to heat.
• These findings highlight the importance of epigenetic regulation in maintaining genome stability against mobile elements.