Convergent adaptive evolution in marginal environments: unloading transposable elements as a common strategy among...

Area of Science:

• Evolutionary Biology
• Genomics
• Plant Science

Background:

• Mangrove trees represent independent evolutionary invasions into coastal environments.
• Phenotypic convergence is common in mangroves, prompting investigation into genomic convergence.
• Transposable elements (TEs) are major components of plant genomes and influence genome size.

Purpose of the Study:

• To investigate the evolutionary dynamics of transposable elements (TEs) in mangrove genomes.
• To understand the relationship between TE evolution and genome size reduction in mangroves.
• To identify molecular convergence in mangrove adaptation.

Main Methods:

• Sequencing of multiple mangrove genomes.
• Analysis of long terminal repeat-retrotransposons (LTR-RTs).
• Estimation of TE death rates using solo-LTRs and truncated elements.

Main Results:

• All mangrove lineages show a significant and convergent reduction in TE loads compared to non-mangrove relatives.
• Genome size reduction is an independent consequence of reduced TE loads across six mangrove lineages.
• The rarity of young LTR-RTs in mangroves results from suppressed element origination (fewer births), not increased death rates.

Conclusions:

• Mangrove genomes exhibit a convergent strategy of TE load reduction.
• This reduction is achieved by suppressing the origination of new transposable elements.
• This genomic adaptation is crucial for mangroves' independent colonization of intertidal zones.