Neurospora crassa F-Box proteins influence carbon source sensing and utilization

Filamentous fungi are capable of degrading plant biomass through the secretion oflignocellulolytic enzymes. However, the industrial exploitation of this potential is limited bycarbon catabolite repression (CCR), a conserved regulatory mechanism that suppressesenzyme production in the presence of readily metabolizable sugars such as glucose. F-box proteins, which mediate targeted protein degradation via the ubiquitin-proteasomesystem, are known to influence lignocellulose signaling and CCR, but their specific roles infilamentous fungi remain largely unexplored. In this study, we used the Neurospora crassagene deletion collection to screen all available strains lacking putative F-box genes (40)for CCR-related phenotypes during carbon source switches between glucose andcellulose. Six proteins with either strongly derepressed or repressed phenotypes werethen selected for further investigation. Transcriptomic profiling revealed significantalterations in the expression of CAZyme genes and sugar transporters during carbonsource transitions. Moreover, immunoprecipitation of GFP-tagged F-box proteins followedby mass spectrometry identified the potential interaction partners, including key factors ofcellulose metabolism and its regulation. These findings provide new insights into the post-translational regulation of carbon source utilization in filamentous fungi and highlight F-boxproteins as promising targets for rational strain engineering to enhance enzymeproduction for biotechnological applications.