The Function of the Plant Double Strand Break Initiating Proteins SPO11-1 and SPO11-2 Is Sequence and to a Certain Extent Species Specific

In most sexually reproducing organisms meiosis plays a key role, by dividing the chromosome set in half before forming gametes. Early during prophase I meiotic recombination is started by the initiation of double strand breaks (DSBs), leading to physical connections between homologous chromosomes and the exchange of genetic material between them. In nearly all analyzed eukaryotic organisms the initiation of meiotic DSBs depends on the meiotic specific protein SPO11. Whereas in animals and fungi only a single SPO11 is present and sufficient for the initiation of meiotic DSBs, plants encode for at least two meiotically active SPO11 proteins (SPO11-1 and SPO11-2), which are both essential for the initiation of meiotic DSBs. We could identify in all so far sequenced land plants homologous genes to Arabidopsis SPO11-1 and -2, which share a common gene structure. We analyzed various plant species and could show that each species possesses a unique pattern of aberrantly spliced gene products of SPO11-1 and -2. By exchanging the endogenous SPO11 genes from Arabidopsis with genes from different plants and other organisms, we were able to show a species specific function of SPO11. The exchange of non conserved regions between SPO11-1 and -2 gave a first hint that the function of each of the two SPO11 genes is also sequence specific.