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, CxrA(Δ207–733) is required for the regulatory functions of whole CxrA, and contains a DNA-binding domain (CxrA(Δ1–16&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 CxrA(Δ1–60). Overexpression of prmt2 in P. oxalicum increases PPDE production by 41.4–95.1% during growth on Avicel, compared with the background strain Δku70;hph(R+). Another arginine N-methyltransferase, PRMT3, appears to assist entry of CxrA into the nucleus, and interacts with CxrA(Δ1–60) 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.