The transcription factor PoMbp1 promotes the growth and development of Pleurotus ostreatus by regulating polysaccharide utilisation

The P. ostreatus has high nutritional and medicinal value and has been used in mycelium-based composites development and sustainable remediation of heavy metals. But the growth and development of P. ostreatus is still unclear.

In this study, the analysis of the biological function of PoMbp1 found that PoMbp1 contain an APSES domain and localizes to the nucleus, indicating it belong to the fungal-specific APSES transcription factors family. The expression pattern analysis showed that PoMbp1 is highly expressed in the fruit body of P. ostreatus, preliminarily indicated that PoMbp1 may play an important role in the development of P. ostreatus fruiting bodies.

To determine the effect of PoMbp1 on the development of P. ostreatus, then we overexpressed and interfered PoMbp1 in P. ostreatus using the ATMT method. The results showed that PoMbp1 interfering strains repressed the mycelial growth rate and prolonged the fruit body development process, while PoMbp1 overexpression strains slightly promoted the mycelial growth rate and the fruit body development. Those results indicated that PoMbp1 played positive role in the development of P. ostreatus.

Then the transcriptomic analysis was performed to investigate the mechanism by which PoMbp1 regulates the development of P. ostreatus. Total differently expressed genes between PoMbp1 transformants and WT strains were obtained at different developmental stages. Then the DEGs were used for WGCNA analysis and it was found that the DEGs in the modules that related to the development were enriched in carbohydrate metabolism. Further analysis of the expression pattern of those gene showed PoMbp1 promotes the expression of genes in polysaccharide catabolic and PoMbp1 overexpressed strains great faster significantly when polysaccharide as carbon source. All those results indicated that PoMbp1 may promote the growth of P. ostreatus by regulating the polysaccharide catabolic and utilisation.

The carbon catabolite repression (CCR) system determines the hierarchy of carbon substrate utilization in filamentous fungi, which ensures preferential utilization of easily metabolizable carbon by preventing the utilization of difficultly metabolizable carbon sources. In this study, the expression level of Snf1 which can phosphorylates CreA (the core transcription factor of CCR) and consequently promote the cellulase expression and cellulose utilisation is upregulated in the PoMbp1 overexpressed strains. Those results indicate that PoMbp1 overexpression can inhibit the activity of CreA, and promote polysaccharide utilisation and conversion, providing a new strategy for improving substrate utilization in edible fungus cultivation and production. However, it remains unclear whether PoMbp1 directly regulated gene expression in CCR system or whether regulation occurs through a different mechanism. The regulatory mechanism of PoMbp1 needs to be further studied.