The Arabidopsis Thaliana DSB FORMATION(AtDFO), A Novel Gene, Is Required For Meiotic Double Strand Break Formation

DNA Double Strand Break (DSB) formation is the initial event for meiotic recombination catalyzed by the conserved Spo11protein. In yeast, nine other genes have been identified to be involved in DSB formation. However, because of the rapid divergence of protein sequence of DSB forming proteins, it is hard to find the DSB formation proteins just based on the sequence blast. This cause the slow progress of the research on DSB formation mechanism in higher eukaryotes. In Arabidopsis, five proteins have been reported to function in DSB formation.Here, we report a new member of DSB forming genes in Arabidopsis, AtDFO. The Atdfo-1mutant shows severely reduced fertility, producing polyads with abnormal number of microspores, unlike tetrads in the wild type. The Atdfo-1meiocytes are defective in homologous chromosome pairing and synapsis. Genetic analysis reveals that homologous recombination of Atdfo-1is severely affected in meiotic prophase I. AtDFO encodes a novel protein without a conserved domain. Besides, no homologues of AtDFO have been identified beyond the plant kingdom, indicating that AtDFO is a plant specific protein. AtMRE11has been reported to be responsible for processing SPO11-generated DSBs. The Atmrell-4mutant generates chromosome fragmentation during meiosis. However, the Atdfo-1Atmre11-4double mutant had no chromosome fragmentation, indicating that AtDFO is required for DSB formation. AtDFO is a new gene required for DSB formation. The identification of AtDFO will not only add a new member of DSB formation proteins, but it will facilitate to understand the mechanism of DSB formation in plant and the evolution process of DSB forming proteins.