What Comparative Genomics Tells Us About the Evolution of Eukaryotic Genes Involved in Recombination

The growing number of completely deciphered genomic sequences provides an enormous reservoir of data, which can be used for addressing questions related to functional and evolutionary biology. The wealth of this approach is documented by the fast growing numbers of recent publications in the field of evolutionary biology based on comparative genomics. Many proteins of the recombination machinery are conserved between plants, fungi and animals but some of them also show remarkable differences regarding their presence, copy number or molecular structure. For example, the protein responsible for double strand break (DSB) induction during meiosis, SPO11, which is related to the subunit A of the archaebacterial topoisomerase VI, is coded by a single gene in animals and fungi. In contrast, plants harbour three distantly related homologues, which seem to have non-redundant functions either in meiosis or in somatic cells and are indispensable for viability. Moreover, plants possess a homologue of the subunit B of the archaebacterial topoisomerase VI, not present in other eukaryotes. We also summarise the recent progress in the usage of genomic data to analyse the evolution of other DNA recombination factors. Finally, several recent studies report on a strong conservation of a reasonable number of intron positions between plants, animals and fungi. This kind of study provides a basis for comparative genomic analyses across kingdoms and demonstrates the existence of ancient introns, a topic of intensive debate.