Abstract White rot fungi are the only organisms that can completely degrade lignin in the plant cell walls. However, the regulatory mechanisms controlling the expression of lignin-modifying enzyme (LME) genes are still obscure. In this study, we investigated the expression of LME genes in the selective lignin-degrading fungus Gelatoporia subvermispora grown on media supplemented with Kraft lignin or lignin-derived aromatic compounds. qRT-PCR analyses showed significant differences in the gene expression of LMEs among cultures exposed to distinct aromatic compounds and Kraft lignin. Intriguingly, the relative expression patterns of LME genes in the presence of Kraft lignin strongly correlated with those observed in cultures amended with coniferyl alcohol or ferulic acid. In particular, the expression of lcc1 and lcc4 was robustly induced by Kraft lignin, ferulic acid, and coniferyl alcohol. To confirm whether lcc1 and lcc4 promoters contain cis -element(s) responsible for this induction, these promoter sequences were fused with the luminous shrimp luciferase gene Nano Luc and knocked in into the pyrG locus of G. subvermispora via CRISPR/Cas9 gene targeting. Transformants harboring the 3139-bp lcc1 promoter or the 2000-bp lcc4 promoter exhibited markedly elevated luciferase activity when medium was supplemented with Kraft lignin/coniferyl alcohol/ferulic acid compared to the control. While transformants containing the truncated 723-bp lcc1 promoter or the 913-bp lcc4 promoter mostly lacked inducible luciferase activity under the same conditions. These results indicated the specific transcriptional regulation is directed by these promoter sequences in G. subvermispora.
Nguyen et al. (Mon,) studied this question.