Affiliation: School of Medicine, Curriculum in Genetics and Molecular Biology
During prophase of meiosis I, homologous chromosomes pair, synapse and exchange DNA by recombining through crossovers (COs). Recombination is necessary in many organisms for correct chromosome segregation, and thus fertility, including in humans and the plant Arabidopsis thaliana (Osman et al., 2011). The enzyme(s) that resolves what is thought to be the main intermediate DNA structure of recombination, a double Holliday junction (dHJ), remains elusive in most eukaryotes including in Arabidopsis. Three nuclear endonucleases have been found resolve eukaryotic HJs in vitro: Mus81-Mms4 (EME), Slx1-Slx4 and, Yen1/GEN1. AtMUS81 generates about 15% of all COs (Berchowitz et al., 2007), while the two homologs of the SLX1-SLX4 complex have been identified but remain to be characterized (At2g30350 and At5g43210). In humans Mus81-Mms4 (EME), Slx1-Slx4 have been found to work in the same pathway, which is separate from GEN1’s activity (reviewed by (West et al., 2015)). Arabidopsis has two Yen1/GEN1orthologs: AtGEN1 (At1g01880) and AtSEND1 (At3g48900). Two recent studies in Arabidopsis have characterized these genes. Bauknecht and Kobbe demonstrated that both AtGEN1 and AtSEND1 have dHJ resolving activity in vitro (Bauknecht and Kobbe, 2014). Olivier et. al went more deeply into understanding the role of AtGEN1 and AtSEND1 in DNA repair and meiosis (Olivier et al., 2015). This is the first characterization of these genes in Arabidopsis and revealed that knockout of AtGEN1 and AtSEND1 single and double mutants do not show growth defects, sensitivity to DNA damage or infertility. They also demonstrated that the combined loss of AtMUS81 and AtSEND1 leads to severe developmental defects, while the same is not the case upon the loss of AtMUS81 and AtGEN1. They also found that AtSEND1 is an important backup in genome stability upon the loss of AtMUS81. In this study we investigate whether AtGEN1 has a role in Arabidopsis HR. Our preliminary data shows that insertional T-DNA mutant alleles of AtGEN1 have altered recombination frequencies, thus AtGEN1 may be involved in HJ resolution in Arabidopsis meiotic recombination.