Phosphoproteomic Insights into the Metabolic Reprogramming of Cell Growth and Lipid Accumulation in <i>Mucor circinelloides</i>

<i>Mucor circinelloides</i> is a model oleaginous fungus for studying microbial lipid accumulation, yet the post-translational mechanisms coordinating growth and lipid biosynthesis remain poorly understood. Here, we present the first systematic quantitative phosphoproteomic analysis of <i>M. circinelloides</i> across its life cycle, encompassing spores and mycelia at 6 h, 24 h (nitrogen depletion), and 96 h. A total of 1252 phosphoproteins and 1682 phosphopeptides were identified, revealing a phosphorylation-driven transition from growth-associated processes to lipid metabolism under nitrogen limitation. Dynamic phosphorylation of key enzymes, notably ATP-citrate lyase (ACL) and Acyl-CoA synthetase (ACS), directly mediated carbon flux redirection toward fatty acid synthesis. A conserved serine-rich motif in ACL suggests an evolutionarily conserved regulatory strategy for lipid accumulation. Integration with fluxomics and proteomics reveals a hierarchical network linking signaling, enzyme phosphorylation, and metabolic reprogramming. These findings provide new insights into phosphorylation-based regulation of fungal growth and lipid biosynthesis in oleaginous fungi.