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

Abstract

ABSTRACT 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 Δcfg1 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. IMPORTANCE In fungal biology, the morphological transition from vegetative hyphae to thick-walled, lipid-rich chlamydospores represents a fundamental developmental switch into dormancy, crucial for survival under environmental stress. Understanding the regulatory mechanisms behind this process is essential for deciphering the basic principles of fungal cell differentiation and adaptation. This study employs multi-omics approaches to systematically characterize chlamydospore formation and identifies the Gti1/Pac2 family protein CFG1 as a master regulator. Functional analysis reveals that CFG1 governs this transition by directly influencing lipid metabolism—a key pathway for spore maturation and structural integrity. These findings uncover a previously unknown molecular switch in fungal development and provide new insights into how filamentous fungi coordinate metabolic reprogramming with cellular differentiation to ensure long-term survival. In fungal biology, the morphological transition from vegetative hyphae to thick-walled, lipid-rich chlamydospores represents a fundamental developmental switch into dormancy, crucial for survival under environmental stress. Understanding the regulatory mechanisms behind this process is essential for deciphering the basic principles of fungal cell differentiation and adaptation. This study employs multi-omics approaches to systematically characterize chlamydospore formation and identifies the Gti1/Pac2 family protein CFG1 as a master regulator. Functional analysis reveals that CFG1 governs this transition by directly influencing lipid metabolism—a key pathway for spore maturation and structural integrity. These findings uncover a previously unknown molecular switch in fungal development and provide new insights into how filamentous fungi coordinate metabolic reprogramming with cellular differentiation to ensure long-term survival.