PEG-Mediated Protoplast Transformation of Penicillium sclerotiorum (scaumcx01): Metabolomic Shifts and Root Colonization Dynamics

Protoplast-based transformation is a vital tool for genetic studies in fungi, yet no protoplast method existed for <i>P. sclerotiorum</i>-scaumcx01 before this study. Here, we optimized protoplast isolation, regeneration, and transformation efficiency. The highest protoplast yield (6.72 × 10⁶ cells/mL) was obtained from liquid mycelium after 12 h of enzymatic digestion at 28 °C using Lysing Enzymes, Yatalase, cellulase, and pectinase. Among osmotic stabilizers, 1 M MgSO₄ yielded the most viable protoplasts. Regeneration occurred via direct mycelial outgrowth and new protoplast formation, with a 1.02% regeneration rate. PEG-mediated transformation with a hygromycin resistance gene and <i>GFP</i> tagging resulted in stable <i>GFP</i> expression in fungal spores and mycelium over five generations. LC/MS-based metabolomic analysis revealed significant changes in glycerophospholipid metabolism, indicating lipid-related dynamics influenced by <i>GFP</i> tagging. Microscopy confirmed successful colonization of tomato roots by <i>GFP</i>-tagged scaumcx01, with <i>GFP</i> fluorescence observed in cortical tissues. Enzymatic (cellulase) seed pretreatment enhanced fungal colonization by modifying root surface properties, promoting plant-fungal interaction. This study establishes an efficient protoplast transformation system, reveals the metabolic impacts of genetic modifications, and demonstrates the potential of enzymatic seed treatment for enhancing plant-fungal interactions.