The Gti1/Pac2 family protein CFG1 controls fungal chlamydospore formation through orchestrating cell wall remodeling, lipid metabolism, and ribosome biogenesis
Aug 2026· Applied and Environmental Microbiology· 0 citations· 66 references
Medicine
TL;DR
It is shown 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, indicating the entry of cells into dormancy.
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.
A physical interaction is identified between AaSlt2 and Swi6/RlmA, suggesting that these components are critical for cell wall synthesis, which advances the understanding of pathogenic mechanisms of A. alternata and proposes potential strategies for controlling postharvest diseases.
Rong Li, Yiyang Liu, Li Li et al.· Virulence· 0 citations
Environmental bacteria have abundant signaling systems wired into complex gene regulatory networks to adapt to fluctuating conditions. In Myxococcus xanthus, starvation triggers a developmental program (specialized biofilm) that produces spore-filled multicellular fruiting bodies surrounded by a distinct quiescent state termed peripheral rods. Fruiting body structure as well as the proportion of cells following each fate can be tuned by a large repertoire of signaling proteins, including numerous orphan histidine kinases. Here, we focus on the histidine kinase TodK which was previously demonstrated to influence developmental progression. We find that loss of TodK produces distinct developmental phenotypes that vary with environmental conditions. To quantify these effects, we developed an image-analysis pipeline that measures aggregation and fruiting body patterning during development on nutrient-limited agar. These analyses revealed the todK mutant precociously aggregates particularly at the peripheries of the colony. Under submerged-culture conditions, initial production of aggregates was not accelerated but aggregates exhibited accelerated progression to mature fruiting bodies. Overexpression of active TodK completely blocked fruiting body formation. Molecular analyses demonstrated that TodK overproduction suppressed expression of core developmental regulators including FruA and CsgA (C-signal). Interestingly, protein accumulation of MrpC, necessary for expression of both FruA and the C-signal was not significantly perturbed suggesting TodK silences MrpC transcriptional activity. Together, these findings establish TodK as a modulator of developmental progression and demonstrate how quantitative phenotyping approaches can reveal biologically meaningful functions for orphan histidine kinases whose mutant phenotypes might otherwise appear subtle. Summary Statement Quantitative analysis of multicellular development reveals previously hidden functions of an orphan histidine kinase, highlighting the importance of robust phenotyping approaches for understanding bacterial signaling networks.
Christopher Mataczynski, Maike M. Glaser, Stuart Huntley et al.· bioRxiv· 0 citations
Colletotrichum fructicola, the primary causal agent of Glomerella leaf spot (GLS), is a destructive fungal pathogen of apple, whose underlying pathogenic mechanisms remain largely unknown. A previous transcriptomic analysis of infected leaves indicated induction of the transcription factor CfMBZ1. This study confirmed that CfMBZ1 is highly expressed in conidia and during early infection. To elucidate its function, we generated a ΔCfMBZ1 deletion mutant via homologous recombination. Phenotypic analysis revealed that ΔCfMBZ1 lost pathogenicity on apple leaves due to a blockage in appressorium-mediated host penetration, despite retaining the ability to form penetration pegs on cellophane. However, extension of invasive hyphae and necrotrophic growth in wounded apple fruit were unaffected. The mutant also exhibited defects in maintaining the integrity of the cell wall and cell membrane, as well as in tolerating oxidative and acid–base stress. Comparative transcriptome analysis suggested that CfMBZ1 regulates appressorium-mediated penetration by modulating genes involved in peroxisome biogenesis, lipid droplet metabolism, and other penetration-related pathways. Our findings reveal that CfMBZ1 plays a critical role in the pathogenesis of Glomerella leaf spot caused by C. fructicola.
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Density dependence is a key characteristic of quorum sensing (QS) in fungi; however, no relevant reports have been found in Monascus. Therefore, this study aimed to investigate the effects of initial spore density on the morphological development and polyketide secondary metabolism of Monascus purpureus to elucidate the regulatory role of QS. At the high initial spore density, more active conidial development and secondary metabolism were observed in the early fermentation stage, accompanied by rougher hyphal surfaces, increased secretion and larger vacuoles. Gene set enrichment analysis (GSEA) based on transcriptomic data revealed that high initial spore density activated ribosome biosynthesis to support rapid cell growth and secondary metabolism, whereas low initial spore density upregulated genes associated with peroxisome biosynthesis, the enzymatic antioxidant system, fatty acid degradation, fatty acid biosynthesis, and asexual sporulation. Furthermore, the reduction in linoleic acid content at high initial spore density suggested that linoleic acid and its derivatives may function as putative quorum sensing molecules (QSMs). Finally, a potential regulatory network integrating initial spore density with secondary metabolism and development was proposed. These findings enhance the understanding of the QS network in Monascus and offer a theoretical basis for the optimization of fermentation processes.
Jiaxing Li, Huijing Zhang, Xizi Zhang et al.· Journal of food microbiology· 0 citations
Sugarcane smut, caused by S. scitamineum, results in substantial economic losses across global sugarcane growing areas. Elucidating the pathogenic mechanisms of S. scitamineum is therefore crucial for developing effective disease control strategies. Our previous work has shown that the protein phosphatase SsPpe1 regulates mating and pathogenicity in S. scitamineum. In this study, we identified SsRts1 as a novel interacting protein of SsPpe1, which contains a PP2A regulator subunit B56 domain. Deletion of Ssrts1 gene impaired sporidia growth, resulting in pseudohyphal sporidia with multiple nuclei and aberrant chitin distribution. Further analysis revealed elevated phosphorylation levels of the cell cycle-related kinase CDK1T161 in the ΔSsrts1 mutants, suggesting that SsRts1 participates in mitosis regulation. Moreover, the ΔSsrts1 mutants exhibited increased sensitivity to cell wall, oxidative and high osmotic stresses. Mechanistically, SsRts1 negatively regulates the phosphorylation levels of the CWI-MAPK Mps1, implicating that SsRts1 is involved in regulating the cell wall integrity (CWI) pathway. Additionally, deletion of Ssrts1 also led to abnormal accumulation of autophagosome, along with defects in sexual mating, filamentation, and virulence. Global transcriptome profiling indicated that SsRts1 modulates ATPase activity, cell cycle progression, transmembrane transport, and tryptophan metabolism. Notably, exogenous supplementation with tryptophan partially restored the mating and filamentation defects in the ΔSsrts1 mutants, indicating that SsRts1 modulates these processes partly through the tryptophan catabolism pathway. Collectively, these findings provide insight into the regulatory roles of PP2A regulatory subunit SsRts1 in S. scitamineum, and expand our understanding of PP2A function in plant-pathogenic fungi.
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Male sterility is a vital trait for hybrid seed production. However, the synergistic coordination between sugar metabolism and reactive oxygen species (ROS) during pollen development remains poorly understood. Here, we identified a plastid-localized hexokinase, CsHXK3, that participates in both processes in cucumber (Cucumis sativus L.). CsHXK3 is localized to the tapetum, microspores, and vascular tissues of the anther. The significant downregulation of CsHXK3 expression in cell wall invertase 3-silenced (CsCWIN3-RNAi) lines supports its essential role in downstream hexose utilization. Biochemical analysis confirmed that CsHXK3 is a glucose-preferring enzyme that is essential for hexose phosphorylation. The CRISPR/Cas9-mediated knockout of CsHXK3 resulted in severe male sterility, characterized by defective tapetal programmed cell death, collapsed pollen grains, and severely impaired pollen germination. Loss of CsHXK3 led to reduced accumulation of sugars (glucose, fructose, and sucrose) and starch in the anthers, accompanied by substantially downregulated expression of sugar transporter genes, including Sugars Will Eventually be Exported Transporters (CsSWEETs) and Sugar Transport Protein 13 (CsSTP13). CsHXK3 deficiency disrupted ROS homeostasis by reducing hydrogen peroxide (H2O2) levels, which was accompanied by the downregulated expression of the ROS-generating gene Respiratory Burst Oxidase Homolog B (CsRBOHB) and upregulated expression of genes encoding ROS-scavenging peroxidases. Our findings indicate that CsHXK3 may coordinate carbohydrate metabolism with ROS homeostasis during pollen development, offering insights into the metabolic regulation of male reproductive success in plants.
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