A multilayered regulatory network mediated by protein phosphatase 4 controls carbon catabolite repression and de-repression in Magnaporthe oryzae

Abstract

Carbon catabolite repression (CCR) and de-repression (CCDR) are critical for fungal development and pathogenicity, yet the underlying regulatory mechanisms remain poorly understood in pathogenic fungi. Here, we identify a serine/threonine protein phosphatase catalytic subunit, Pp4c, as essential for growth, conidiation, virulence, and the utilization of carbohydrates and lipids in Magnaporthe oryzae. We demonstrate that the protein phosphatase 4 complex (Pp4c and Smek1 subunits), the AMP-activated protein kinase (AMPK) Snf1, and the transcriptional regulators CreA (repressor) and Crf1 (activator) collaboratively regulate the utilization of non-preferred carbon sources. Protein interaction and phosphorylation analyses reveal that under glucose-rich conditions, Snf1 and Smek1 directly regulate the phosphorylation status of CreA and Crf1. In contrast, under l-arabinose-rich conditions, Snf1 indirectly modulates the dephosphorylation of these transcription factors via Pp4c and Smek1. Phosphorylation-mediated activation or inactivation of CreA and Crf1 drives CCR and CCDR, thereby governing the metabolism of carbon sources derived from plant cell walls and contributing to fungal pathogenicity. These findings provide deep insights into the regulation of CCR and CCDR, emphasizing their significance in carbon metabolism and pathogenicity in phytopathogenic fungi.