Rapid DNA Loss as a Counterbalance to Genome Expansion through Retrotransposon Proliferation in Plants

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 106; no. 42; pp. 17811 - 17816
• Main Authors: Hawkins, Jennifer S., Proulx, Stephen R., Rapp, Ryan A., Wendel, Jonathan F.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 20.10.2009; National Acad Sciences
• Subjects: Base Sequence; Biological Sciences; Biological taxonomies; Biological variation; Chromosomes, Artificial, Bacterial - genetics; Comparative analysis; copy number; Data processing; Deoxyribonucleic acid; Diploids; DNA; DNA Primers - genetics; DNA, Plant - genetics; Evolution; Evolution, Molecular; Flowers & plants; Genetic transposition; Genome size; Genome, Plant; Genomes; Genomics; Gossypium; Gossypium - classification; Gossypium - genetics; homologous recombination; Models, Genetic; Nucleotide sequence; Obesity; Phylogeny; Polymerase chain reaction; Retroelements - genetics; Retrotransposons; Species Specificity; Taxa; Terminal Repeat Sequences; Time Factors; Transposons
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0904339106

Transposable elements, particularly LTR-retrotransposons, comprise the primary vehicle for genome size expansion in plants, while DNA removal through illegitimate recombination and intrastrand homologous recombination serve as the most important counteracting forces to plant genomic obesity. Despite extensive research, the relative impact of these opposing forces and hence the directionality of genome size change remains unknown. In Gossypium (cotton), the 3-fold genome size variation among diploids is due largely to copy number variation of the gypsy-like retrotransposon Gorge3. Here we combine comparative sequence analysis with a modeling approach to study the directionality of genome size change in Gossypium. We demonstrate that the rate of DNA removal in the smaller genomes is sufficient to reverse genome expansion through Gorge3 proliferation. These data indicate that rates of DNA loss can be highly variable even within a single plant genus, and that the known mechanisms of DNA loss can indeed reverse the march toward genomic obesity.