Overexpression of a putative transcription factor Gf.CRZ1 affects the expression of oxalate-degrading genes and causes morphological defects during mycelium formation in Grifola frondosa

Grifola frondosa is commercially produced year-round in large-scale facilities. However, the molecular mechanisms of fruiting body differentiation remain elusive, and understanding these mechanisms at the molecular genetic level is therefore important for improving the cultivation of this economically important mushroom. In this study, we focused on a previously reported putative transcription factor, Gf.CRZ1, with homology to Saccharomyces cerevisiae Crz1. Gf.CRZ1 is a candidate gene that is predicted to be involved in mutations affecting morphology and that is strongly expressed in some spontaneous mutant strains relative to wild type. Overexpression of Gf.CRZ1 in the wild-type strain leads to increased expression of Gf.ODC1 and Gf.FDH1, which are involved in oxalic acid degradation, similar to that of the mutant strains. Additionally, the Gf.CRZ1-overexpressing strains exhibited morphological defects including reduced colony growth rate and poorly developed aerial mycelia similar to mutant strains. These results suggested that overexpression of Gf.CRZ1 might affect regulation of oxalic acid degradation and be causally related to morphological defects via disturbances in oxalic acid metabolism.