We cloned and sequenced a recQ gene homolog from the basidiomycetous mushroom Lentinula edodes (Le.). This gene, named Le.recQ, was found to have a coding capacity of 945 amino acids (aa) and be interrupted by 11 small introns. The deduced Le.RECQ protein was clearly smaller than other fungal RecQ proteins such as Neurospora crassa QDE3 (1955 aa), Schizosaccharomyces pombe Rqh1 (1328 aa), and Saccharomyces cerevisiae SGS1 (1447 aa). It exhibited the highest homology to the Arabidopsis thaliana RecQl4A protein (1182 aa) in its size and aa sequence. Northern-blot analysis showed that the Le.recQ gene is transcribed at similar levels during mycelial development in L. edodes fruiting-body formation on a sawdust-corn bran medium. The L. edodes dikaryotic mycelial cells, which had been vegetatively grown in SMY liquid medium, were found to contain a clearly larger amount of Le.recQ transcript than the L. edodes two compatible monokaryotic mycelial cells. Expression of Le.recQ cDNA in S. cerevisiae might partially complement defects associated with the loss of its homolog S. cerevisiae SGS1 gene.