In the study by Nakazawa et al. (2023b), the authors claim that the sextuple deletion of vp2, vp3, mnp2, mnp3, mnp6, and lac2 in P. ostreatus results in a near-complete loss of lignin-degrading ability on beech wood sawdust (BWS), presenting it as direct evidence of the essentiality of these lignin-modifying enzymes (LMEs). However, given the functional redundancy often observed among peroxidases and laccases in fungi, how can we be sure that this phenotype is not due to unintended off-target effects or global physiological impairments from multiple gene deletions rather than the absence of these specific enzymes alone? Was there any transcriptomic or proteomic verification to confirm the specificity of the deletions and the lack of compensatory enzyme expression?
