A Rho-Type GTPase Protein Pocdc42 Regulates the Development and Cellulase Expression of Penicillium oxalicum

Penicillium oxalicum is a filamentous fungus widely recognized for its robust production of cellulases. It features complex pathways that govern the triggered expression of these enzymes. Signal transduction serves a critical function in the effective management of cellulase induction and expression. In this investigation, we conducted a screening to identify Pocdc42, a signaling protein found within the Ras signaling pathway of P. oxalicum. The knockout of Pocdc42 resulted in increased cellulase activity in P. oxalicum, along with significantly elevated expression levels of cellulase genes. Moreover, the disruption of Pocdc42 profoundly influenced the growth and development of the strain. The Pocdc42-deficient mutant demonstrated a significant reduction in its ability to produce conidia. The relative transcriptional activities of transcription factors BrlA and StuA, which are associated with conidiation, were 3.6- and 1.9-fold higher in the wild-type strain than in the mutant strain, respectively. In contrast, the gene expression of the transcription factor FlbC remained relatively stable. These results suggest that Pocdc42 is essential for the regulation of cellulase expression, as well as for hyphal growth, development, and conidium formation in P. oxalicum. The results of this study contribute to elucidating the mechanisms underlying the function of the Ras signaling pathway in the regulation of cellulase expression and growth and development in filamentous fungi.