Retrotransposon activation followed by rapid repression in introgressed rice plants

Area of Science:

• Plant molecular biology
• Genomics
• Evolutionary biology

Background:

• Plant retrotransposons are typically dormant but can be activated by environmental or genetic stress.
• Understanding retrotransposon dynamics is crucial for plant genome evolution.

Purpose of the Study:

• To investigate the activation and subsequent repression of rice retrotransposons following interspecific DNA introgression.
• To explore the epigenetic mechanisms, such as DNA methylation, involved in regulating retrotransposon activity.

Main Methods:

• Genomic Southern hybridization to assess copy number changes.
• Northern analysis to detect retrotransposon transcripts.
• Analysis of cytosine methylation patterns in retrotransposon sequences.

Main Results:

• Both copia-like and gypsy-like retrotransposons in rice were activated by DNA introgression from Zizania latifolia.
• Increased retrotransposon copy number correlated with changes in cytosine methylation.
• Retrotransposon activity was ephemeral, with rapid repression observed.
• Mechanisms for repression included DNA hypermethylation and internal sequence deletion.

Conclusions:

• Interspecific DNA introgression can transiently activate rice retrotransposons.
• Epigenetic modifications, particularly DNA hypermethylation, play a key role in rapid retrotransposon silencing.
• Retrotransposon dynamics influenced by introgression have implications for plant genome evolution.