Plant genome size variation: bloating and purging DNA

Area of Science:

• Plant Biology
• Genomics
• Evolutionary Biology

Background:

• Plant genome size is dynamic, involving DNA bloating and purging.
• Historically, plants were thought to continually increase genome size, but recent evidence shows active DNA purging.
• The Kew Plant DNA C-values Database and sequenced genomes aid research.

Purpose of the Study:

• To explore the mechanisms of plant genome size variation.
• To understand the balance between DNA proliferation and purging in plants.
• To investigate the role of retrotransposons and epigenetics in genome size evolution.

Main Methods:

• Comparative genomics of sequenced plant genomes.
• Analysis of retrotransposon proliferation and purging mechanisms.
• Investigation of DNA methylation and epigenomic surveillance.

Main Results:

• Plant genomes primarily bloat via long terminal repeat retrotransposons (LTRs) but actively purge them.
• Mechanisms like recombination and non-homologous end joining facilitate DNA purging.
• Ultra-small genomes (e.g., Utricularia gibba) use genome fractionation and neofunctionalization after whole genome duplication (WGD).
• Large genomes (e.g., Picea abies) show LTR proliferation with less effective purging, potentially lacking WGD.
• Smaller genomes exhibit more aggressive epigenomic surveillance against LTRs than larger genomes.

Conclusions:

• Plant genome size is actively regulated through DNA purging, not just bloating.
• Retrotransposon proliferation and purging mechanisms are key drivers of genome size variation.
• Epigenomic surveillance plays a role in purging young retrotransposons, differing between small and large genomes.
• Genome size may reflect evolutionary status, influenced by these dynamic processes.