Organelle Genomes in Phaseolus Beans and Their Use in Evolutionary Studies

Abstract

Chloroplasts and mitochondria originated from separate endosymbiotic events that occurred about 1.5 billion years ago. In plants, the quadripartite nature of the chloroplast genome is a conserved feature with very little size variation among species. In contrast, size of mitochondrial genomes varies greatly in plants with high rate of rearrangements in angiosperms, although highly conserved in sequence. Sequencing of organelle genomes has increased in the last years as new technologies developed, and today, the Organelle Genome Resources of GenBank contains about 1717 and 275 records of complete chloroplast and mitochondrial genomes for plants, 73 and six of them for legumes, respectively. In plants, plastid genomes have been very useful for phylogenetic and population genetics studies. In Phaseolus beans, polymorphisms in the plastid genome have been used in several studies to unravel the evolutionary history of the common bean and Lima bean in the wild and to pinpoint domestication places. However, all these studies have explored very few genomic regions of the plastid genome. Therefore, new genome resources need to be developed for Phaseolus beans. The sequencing of the plastid genome of the common bean in the year 2007 was a good start, but since then no new organelle genome sequences have been reported in this genus. The goal of this review is to stimulate the development of more organelle genomes resources in the genus Phaseolus, which will allow a better understanding of the rates and patterns of evolution and the dynamics of expression patterns of these genomes. Third-generation sequencing technologies and additional tools offer an opportunity to do so, and in the near future, we should see more developments in this direction.