The Gti1/Pac2 family protein CFG1 controls fungal chlamydospore formation through orchestrating cell wall remodeling, lipid metabolism, and ribosome biogenesis

The morphological transition of fungi from vegetative hyphae to thick-walled chlamydospores enhances their longevity in harsh environmental conditions. Owing to this resilience, pathogenic fungi that form chlamydospores are particularly difficult to control. Therefore, understanding the mechanisms of chlamydospore formation is critically important. Here, we show that the hyphae of the filamentous fungus Trichoderma guizhouense can differentiate into typical terminal and intercalary chlamydospores characterized by double-layered spherical or ellipsoidal cell walls with accumulated lipid bodies and nuclei. We found that during chlamydospore formation, ribosome biogenesis was gradually downregulated, indicating the entry of cells into dormancy. Comparative transcriptomic analyses across developmental stages and media identified the Gti1/Pac2 family protein CFG1 as an essential regulator, as the Δ cfg1 strain failed to form chlamydospores under all inducing conditions. Lipidomic analysis showed its involvement in lipid metabolism, and mutants lacking lipid metabolism genes pdat or dgat produced fewer chlamydospores. Our work reveals the molecular mechanism of chlamydospore formation in T. guizhouense .