Patterns and evolution of nucleotide landscapes in seed plants

Area of Science:

• Genomics
• Molecular Evolution

Background:

• Nucleotide landscapes, or base composition distribution in genomes, vary significantly across species.
• While mutational bias and selection were historically considered primary drivers, GC-biased gene conversion (gBGC) is now recognized as a key factor, especially in vertebrates.
• Plant genome GC content evolution remains less understood, with studies often focusing narrowly on Arabidopsis thaliana and rice, leading to oversimplified dicot/monocot comparisons.

Purpose of the Study:

• To provide a comprehensive analysis of gene GC content across the seed plant phylogeny.
• To investigate the evolutionary mechanisms driving GC content variation in plants.
• To challenge the prevailing dicot/monocot dichotomy in plant genome evolution.

Main Methods:

• Utilized expressed sequence tag (EST) data from over 200 plant species.
• Analyzed gene GC content distribution across diverse seed plant lineages.
• Compared findings with existing models of plant genome evolution.

Main Results:

• Observed continuous variations in GC content across the seed plant phylogeny, rather than a strict dicot/monocot split.
• Identified multiple independent episodes of GC content enrichment.
• GC-poor, homogeneous genomes appear ancestral, evolving towards more GC-rich, heterogeneous genomes.

Conclusions:

• The evolution of GC content in plant genomes is more complex than previously thought.
• GC-biased gene conversion (gBGC) is a likely significant factor in shaping plant genome GC content.
• Future research should consider the broader phylogenetic context when studying plant genome evolution.