Hyper-resistance of meiotic cells to radiation due to a strong expression of a single recA-like gene in Caenorhabditis elegans

Sensitivity of meiotic cells to DNA damaging agents is little understood. W e have demonstrated that the meiotic-pachytene nuclei in the Caenorhabditis elegans gonad are hyper-resistant to X-ray irradiation, but not to UV irra diation, whereas the early embryonic cells after fertilization and the full grown oocytes are not. The Ce-rdh-1 gene [RAD51, DMC1 (LIM15), homolog 1 o r Ce-rad-51], which is essential for the meiotic recombination, is the only bacterial recA-like gene in the nematode genome, and is strongly expressed in the meiotic cells. Following silencing of the Ce-rdh-1 gene by RNA inte rference, the meiotic cells become more sensitive to X-ray irradiation than the early embryonic cells. This is the first report that meiotic cells are hyper-resistant to DNA strand breaks due to the high level of expression o f the enzyme(s) involved in meiotic homologous recombination.