Breeding better crops: lessons from the homologous recombination pathway.

Homologous recombination is a key feature of sexual reproduction, allowing reciprocal exchange of parental chromosome segments. The resulting chromosomal crossovers lead to the merging of DNA segments inherited from different parents, allowing for the accumulation of unique combinations of genetic information on a single molecule. The number of DNA crossover events is tightly controlled and relatively restricted in many organisms, including plants. However, increasing the number of crossover events should theoretically generate a greater number of new phenotypes, some of which may prove beneficial in new environments. Crop breeders, whether intentionally or not, are developing new varieties within the confines of crossover numbers. As such, work describing the mechanism of homologous recombination may provide greater insight into how the process can be modified to enable optimal crop improvement. Here, we provide a comprehensive, up-to-date protein network of homologous recombination processes in plants. It is anticipated that this network will assist in the understanding of plant DNA crossovers and chromosomal segregation during meiosis. In addition to providing this compilation of current understanding, we also assess the extent to which homologous recombination is being altered by breeders, discuss new technologies that could be used to manipulate crossover frequencies and detail research highlighting the potential benefits of embracing this knowledge.