Abstract
The lignocellulose degradation capacity of filamentous fungi has been widely studied because of their cellulase hypersecretion. The p24 proteins in eukaryotes serve important functions in this secretory pathway. However, little is known about the functions of the p24 proteins in filamentous fungi. In this study, four p24 proteins were identified in Penicillium oxalicum. Six p24 double-deletion strains were constructed, and further studies were carried out with the ΔerpΔpδ strain. The experimental results suggested that Erp and Pδ form a p24 heterodimer in vivo. This p24 heterodimer participates in important morphogenetic events, including sporulation, hyphal growth, and lateral branching. The results suggested that the p24 heterodimer mediates protein transport, particularly that of cellobiohydrolase. Analysis of the intracellular proteome revealed that the ΔerpΔpδ double mutant is under secretion stress due to attempts to remove proteins that are jammed in the endomembrane system. These results suggest that the p24 heterodimer participates in morphogenesis and protein transport. Compared with P. oxalicum Δerp, a greater number of cellular physiological pathways were impaired in ΔerpΔpδ. This finding may provide new insights into the secretory pathways of filamentous fungi.
Highlights
The lignocellulose degradation capacity of filamentous fungi has been widely studied because of their cellulase hypersecretion
The colony diameter was slightly reduced for P. oxalicum Δerp, while it was considerably decreased for ΔerpΔpδ [parent strain: 21 ± 0.5 mm, ΔerpΔpδ strain: 15 ± 0.4 mm] (Fig. 3a)
We investigated the function of the p24 heterodimer consisting of Erp and Pδ in P. oxalicum
Summary
The lignocellulose degradation capacity of filamentous fungi has been widely studied because of their cellulase hypersecretion. The number of spores was significantly reduced in the ΔerpΔpδ strain (P = 0.0054, n = 1 8) (Fig. 3b) To further confirm this result, comparison of the sporulation levels of the parent and ΔerpΔpδ strains during submerged cultivation was performed. The colony diameter was slightly reduced for P. oxalicum Δerp, while it was considerably decreased for ΔerpΔpδ [parent strain: 21 ± 0.5 mm (mean ± s.d., n = 3), ΔerpΔpδ strain: 15 ± 0.4 mm (mean ± s.d., n = 3 )] (Fig. 3a) These results indicate that the p24 heterodimer participates in conidiospore formation and hyphal growth. Comparison of extracellular protein concentrations and enzymatic activities between the parent and ΔerpΔpδ strains. Comparison of intracellular protein concentrations and specific enzymatic activities between the parent and ΔerpΔpδ strains. Two rRNA-related proteins (PDE_07738 and PDE_06767) were significantly downregulated in the ΔerpΔpδ strain
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