Isolation of a LIM15/DMC1 homolog from the basidiomycete Coprinus cinereusand its expression in relation to meiotic chromosome pairing

The Escherichia coli gene recA is essential for homologous recombination an d DNA repair, and homologs have been identified in eukaryotes. A basidiomyc ete, Coprinus cinereus, which has many advantages for the study of meiosis, was recently reported to have a homolog of one of these, RAD51. In the yea st Saccharomyces, mutations in the RAD51 gene cause defects in both somatic :and meiotic cells. Based on this finding, we screened-for a meiosis-specif ic homolog of recA, equivalent to Lilium LIM15 or Saccharomyces DMC1, in C. cinereus, and isolated a clone containing a 1.2-kb DNA fragment from a cDN A library constructed with Coprinus poly(A)(+) RNA isolated from cells unde rgoing meiosis. The predicted amino acid sequence was 52% identical to the putative gene product of the lily cDNA clone LIM15 and 61% identical to Sac charomyces DMC1, and: showed limited sequence similarity to the products of RAD52, 55, and 57. The synchrony of meiosis in Coprinus provides an ideal system for the investigation of differential gene expression in relation to meiosis and fruiting body development. Northern analysis indicated that Co prinus LIM15/DMC1 was expressed at meiotic prophase within 8 h after the on set of karyogamy, suggesting that the gene functions mostly at the stage at which the homologous chromosomes pair, but may not be essential at the poi nt at which they recombine. The gene is not expressed in somatic cells.