Abstract
The manipulation of meiotic recombination in crops is essential to develop new plant varieties rapidly, helping to produce more cultivars in a sustainable manner. One option is to control the formation and repair of the meiosis-specific DNA double-strand breaks (DSBs) that initiate recombination between the homologous chromosomes and ultimately lead to crossovers. These DSBs are introduced by the evolutionarily conserved topoisomerase-like protein SPO11 and associated proteins. Here, we characterized the homoeologous copies of the SPO11-1 protein in hexaploid bread wheat (Triticum aestivum). The genome contains threeSPO11-1gene copies that exhibit 93-95% identity at the nucleotide level, and clearly the A and D copies originated from the diploid ancestorsTriticum urartuandAegilops tauschii, respectively. Furthermore, phylogenetic analysis of 105 plant genomes revealed a clear partitioning between monocots and dicots, with the seven main motifs being almost fully conserved, even between clades. The functional similarity of the proteins among monocots was confirmed through complementation analysis of theOryza sativa(rice)spo11-1mutant by the wheatTaSPO11-1-5Dcoding sequence. Also, remarkably, although the wheat and Arabidopsis SPO11-1 proteins share only 55% identity and the partner proteins also differ, theTaSPO11-1-5DcDNA significantly restored the fertility of the Arabidopsisspo11-1mutant, indicating a robust functional conservation of the SPO11-1 protein activity across distant plants. These successful heterologous complementation assays, using both Arabidopsis and rice hosts, are good surrogates to validate the functionality of candidate genes and cDNA, as well as variant constructs, when the transformation and mutant production in wheat is much longer and more tedious.