DNA Polymerase Epsilon Is a Key Component of the Meiotic Recombination Pathway

Meiosis is a crucial progress for sexual reproduction in eukaryotes, during which cell replicates its genome once but divides twice to generate haploid gametes. Unlike mitosis, meiosis has an intricate and elaborate prophase I with homologous chromosomes pairing, synapsis, and recombination. Recent advances of meiosis studies in plants, yeast, Drosophila, C. elegans and mouse are intensively focusing on homolog interaction especially on recombination. However, the understanding of DNA synthesis, a critical step for double strand break repair is still obscure. With the weak mutation allele in DNA polymerase epsilon named pol2a in Arabidopsis, we found that Pole is required for plant fertility and male meiosis. Defects of abnormal chromosome association, fragmentation and segregation were observed in pol2a mutant. By cytological and genetic analysis, we found that POL2A works after double strand break formation, and upstream of RCK in the interference-insensitive CO pathway. However, significant reduced MLH1 foci indicated CO interference pathway is not fully blocked in pol2a mutant. It lets us to hypothesize that sufficient leading strand DNA elongation conducted by POL2A promotes formation of some interference sensitive COs and the rest COs are substituted by Polδ, another pivotal DNA polymerase who is responsible for lagging strand elongation in DNA replication. Further study of the proDMC1:: Polδ^RNAi pol2a-1 transgenic plants showed more severe sterility, chromosome association and fragmentation, providing new evidence for the hypothesis.