The effect of hydroxyurea on meiosis and genetic recombination in the fungus Coprinus lagopus.

Treatment with hydroxyurea (HU) inhibits fruitbody development in Coprinus lagopus (sensu Lewis). The two most sensitive meiotic stages are mid-late premeiotic S phase and the pachytene-diplotene period. A 2 or 4 h treatment at mid-late premeiotic S phase arrests fruitbody development. If the same treatment is given at pachytene and diplotene, the fruitbody completes meiosis but the spores produced are inviable. The spores from fruitbodies treated at pachytene appear to be normal whereas those treated at diplotene are empty because the four nuclei remain in the basidium. A 2 or 4 h treatment with HU during karyogamy causes a decrease in spore viability and a dramatic increase in recombination frequency. The same treatment at metaphase II or later stages causes little damage to fruitbody development or spore viability. The effects of HU on the meiotic cell cycle suggest that the drug exerts its effect by inhibiting the synthesis of deoxynucleotides.