Grass genome structure and evolution.

Abstract

Advances in the construction of large insert libraries and physical maps have facilitated the sequencing of orthologous regions from related plant species that differ in genome size. This approach has been particularly productive for the Poaceae, including many important cereal crops. When the sequences of orthologous regions from closely related species are aligned, we can analyze the details of chromosomal evolution. The dynamics of chromosome structure appears to be driven by two types of rearrangement mechanisms, 'cut and paste' and 'copy and paste'. The latter mechanism has contributed to the expansion of orthologous regions, primarily by transposon amplification, while ongoing deletions by illegitimate and homologous recombination have at least partially counteracted or reversed this expansion in some regions. This review describes the current status of our understanding of the plasticity of plant genomes, emphasizing maize as a model for these studies.