Duplications and Turnover in Plant Genomes

Abstract

Cytologists have long documented differences in chromosome number and organization among plants, but the truly dynamic nature of plant genome evolution is only becoming apparent with fully sequenced and assembled genomes. A major result of these new data is that duplication—of single genes, chromosomes, and whole genomes—is a major force in the evolution of plant genome structure and content. For example, genomic comparisons among divergent animals are able to recover significant signatures of synteny (Hiller et al. 2004), but less divergent flowering plant genomes often demonstrate relatively lower large-scale collinearity because of cycles of polyploidy and diploidization (Tang et al. 2008; Salse et al. 2009). Among individuals and closely related species, copy number variation and changes in gene family size are now recognized as critical sources of genetic variation (Lynch 2007). Duplication and subsequent resolution have yielded a continually changing genome whose elements are constantly turning-over. Although gene and genome duplication has long garnered attention as a potentially important source of evolutionary novelty (Haldane 1933; Stebbins 1950; Ohno 1970), the perspective of a dynamic plant genome fueled by duplication and loss stands in contrast to classical concepts of a largely stable genome. In this chapter we provide an overview of how duplication-driven genomic turn-over has influenced the evolution and diversity of plant genomes.