This study on the evolution of GC content of genome in plants is partly supported by the ARCAD project Comparative populations genomics

The Plant Cell. April 2012. doi: http:/​/​dx.​doi.​org/​10.​1105/​tpc.​111.​093674  

Patterns and Evolution of Nucleotide Landscapes in Seed Plants  

Laurana Serres-Giardi,a,b Khalid Belkhir,a Jacques David,b and Sylvain Glémina,1

a Institut des Sciences de l’Evolution de Montpellier, Unité Mixte de Recherche 5554, Centre National de la Recherche
Scientifique, Université Montpellier 2, F-34095 Montpellier, France
b Montpellier SupAgro, Unité Mixte de Recherche 1334, Amélioration Génétique et Adaptation des Plantes Méditerranéennes et Tropicales, F-34398 Montpellier, France

1Address correspondence to glemin@univ-montp2.fr.  

Abstract

Nucleotide landscapes, which are the way base composition is distributed along a genome, strongly vary among species. The underlying causes of these variations have been much debated. Though mutational bias and selection were initially invoked, GC-biased gene conversion (gBGC), a recombination-associated process favoring the G and C over A and T bases, is increasingly recognized as a major factor. As opposed to vertebrates, evolution of GC content is less well known in plants. Most studies have focused on the GC-poor and homogeneous Arabidopsis thaliana genome and the much more GC-rich and heterogeneous rice (Oryza sativa) genome and have often been generalized as a dicot/monocot dichotomy. This vision is clearly phylogenetically biased and does not allow understanding the mechanisms involved in GC content evolution in plants. To tackle these issues, we used EST data from more than 200 species and provided the most comprehensive description of gene GC content across the seed plant phylogeny so far available. As opposed to the classically assumed dicot/monocot dichotomy, we found continuous variations in GC content from the probably ancestral GC-poor and homogeneous genomes to the more derived GC-rich and highly heterogeneous ones, with several independent enrichment episodes. Our results suggest that gBGC could play a significant role in the evolution of GC content in plant genomes.

Published online before print April 2012