Plants constitute an essential pillar of earths ecosystem and they are the most important source for
human nutrition. If we want to understand how plants evolve, how to utilize their valuable traits and
how to devise smart plant breeding programs we have to study the molecular mechanisms of meiosis.
Meiosis is a specialized, two-step cell division that ensures the reduction of the genome prior to the
formation of generative cells. It is during meiosis, that genetic information between maternal and
paternal chromosomes is mutually exchanged, leading to novel combinations of genetic traits in the
following generation.
Meiotic recombination is initiated by DNA double strand breaks (DSBs). Specific DSB promoting
proteins, among them the topoisomerase-related SPO11, introduce DSBs at various positions
throughout the genome. Dedicated DNA repair mechanism ensure that the breaks are repaired in such
a manner that maternal and paternal chromosomal parts become mutually exchanged. Given the
importance of the DSB forming complex in determining the sites and the frequency of genetic
exchange it is surprising that the biochemical characteristics of this complex have not yet been
elucidated.
The proposed project aims at the thorough characterization of the meiotic DSB complex of the model
plant Arabidopsis thaliana. Having successfully mastered heterologous protein production for all
complex members biochemical and structural analyses are now feasible. The superordinate question is,
if SPO11 (together with its partner MTOPVIB) performs a bona-fide type II topoisomerase-like
reaction or a variation thereof. Current models of meiotic break formation suggest a reaction mode,
with SPO11 becoming covalently linked to the 5 end of DNA at the scission site. While reversibility
of this reaction appears in principle possible, it has never been tested experimentally. Understanding
the biochemistry of meiotic DSB formation is key to generate a comprehensive model of genetic
exchange.