Transposons in cereals: Shaping genomes and driving their evolution

Abstract

The large amount of genomic information available from grass species and in particular the completely sequenced genomes of Sorghum, Brachypodium, rice and maize offer the possibility to analyze the role of transposable elements (TE) in genome evolution. Genome-wide comparisons revealed molecular processes known as genomic turnover and gene movement, which have been associated with TEs. Genomic turnover is responsible for the differences in genome sizes in cereals, where genome size increases due to LTR retrotransposon activity and decreases due to mechanisms of unequal homologous recombination and illegitimate recombination. Gene movement is the result of double-strand break repair processes after the excision of a TE, a process which patches up gaps in the genome and moves or duplicates gene fragments. The future availability of complete genome sequences from more grass species, in particular the large wheat and barley genomes, will allow to improve our knowledge on the contribution of specific TE families on genome evolution.