The Variation of Base Composition in Plant Genomes

Abstract

The proportions of the four nucleotides in DNA may vary significantly in various genome components and with different selective forces or mutation biases acting on particular sequences. Most frequently, DNA base composition is expressed as the percentage of guanine (G) and cytosine (C) bases (i.e., GC content). The study of GC content has a long tradition in prokaryotic biology and systematics, and has been widely discussed in animal genomics namely, in the consequences of the evolution of the isochore structure of humans and other warm-blooded vertebrates. However, less attention has been paid to the GC content of plant genomes. Here, we survey existing research concerning GC content of plant nuclear genomes and outline some directions for possible interpretations of the biological relevance of variation in GC content viewed in the context of work done on bacterial and animal genomes. We briefly discuss major physical and chemical differences between GC and AT base pair and summarize existing opinions on the mechanisms of local or genome-wide GC content variation, including namely compositional variation, neutral mutational biases, and various selective reasons. In addition to the brief survey of plant genomic GC contents, most frequent methods for GC content measurements in plants are also outlined.