Arginine methyltransferases PRMT2 and PRMT3 are essential for biosynthesis of plant-polysaccharide-degrading enzymes in Penicillium oxalicum

Many filamentous fungi produce plant-polysaccharide-degrading enzymes (PPDE); however, the regulatory mechanism of this process is poorly understood. A Gal4-like transcription factor, CxrA, is essential for mycelial growth and PPDE production in Penicillium oxalicum. Its N-terminal region, CxrAΔ207–733 is required for the regulatory functions of whole CxrA, and contains a DNA-binding domain (CxrAΔ1–16&Δ59–733) and a methylated arginine (R) 94. Methylation of R94 is mediated by an arginine N-methyltransferase, PRMT2 and appears to induce dimerization of CxrAΔ1–60. Overexpression of prmt2 in P. oxalicum increases PPDE production by 41.4–95.1% during growth on Avicel, compared with the background strain Δku70;hphR+. Another arginine N-methyltransferase, PRMT3, appears to assist entry of CxrA into the nucleus, and interacts with CxrAΔ1–60 in vitro under Avicel induction. Deletion of prmt3 resulted in 67.0–149.7% enhanced PPDE production by P. oxalicum. These findings provide novel insights into the regulatory mechanism of fungal PPDE production.