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Genetic determinants that permit growth without the core septin Cdc12 in Cryptococcus neoformans

ABSTRACT: Septins are conserved cytoskeletal GTPases that regulate morphogenesis, cytokinesis, and cell-surface organization in fungi. In most model and pathogenic yeasts, including Saccharomyces cerevisiae and Candida albicans, core septin subunits such as Cdc3 and Cdc12 are essential and their loss results in lethal cytokinetic defects. In Cryptococcus neoformans, by contrast, deletion of CDC12 yields viable cells that grow normally under permissive conditions, raising the question of how this pathogen maintains cell integrity without a functional septin complex. To address this, we compared the transcriptomes of wild-type cells and a cdc12Δ mutant. The cdc12Δ strain showed a focused set of transcriptional changes, with induction of genes involved in cell wall remodeling, stress-dependent morphogenetic programs, and pathways that promote fitness under compromised cytoskeletal conditions. Genetic analysis of the most highly induced genes uncovered factors that contribute to proliferation in the absence of Cdc12, including a previously uncharacterized aspartic-type endopeptidase that becomes essential when septin function is lost. These findings outline the compensatory circuitry that permits septin-independent growth in C. neoformans and help explain why this pathogen can tolerate septin loss. This intrinsic plasticity highlights C. neoformans as a powerful comparative model for studying the evolution and function of septin complex in fungal cell biology.

ORGANISM(S): Cryptococcus neoformans

PROVIDER: GSE315847 | GEO | 2026/01/12

REPOSITORIES: GEO

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Project description:Metabolically quiescent pathogens can persist in a viable non-replicating state for months or even years. In specific infectious diseases, such as tuberculosis, cryptococcosis, histoplasmosis, latent infection is a corollary of this dormant state, with at some point a phase of reactivation, leading to the symptoms of the infection. During murine cryptococcosis and macrophage uptake, stress and host immunity induce C. neoformans heterogeneity with generation of a sub-population of yeasts that has been shown to harbor a phenotype compatible with dormancy (low stress response, latency of growth). In this subpopulation, mitochondrial transcriptional activity has been shown to be up regulated and this phenotype has been considered as a hallmark of quiescence in stem cells. Based on these findings, we worked to reproduce this phenotype in vitro model and standardized the experimental conditions to generate dormancy in Cryptococcus neoformans. We found that incubation of stationary phase yeasts (STAT) in nutriment limited conditions and hypoxia during 8 days (8D-HYPOx) were able to mimic the phenotype obtained in vivo. In these conditions, mortality and/or apoptosis occurred in less than 5% of the yeasts compared to 30-40% of apoptotic or dead yeasts upon incubation in normoxia (8D-NORMOx). Yeasts in 8D-HYPOx harbored a lower stress response, delayed growth and less that 1% of culturability on agar plates, suggesting that these yeasts are viable but non culturable cells (VBNC). These VBNC were able to reactivate in the presence of pantothenic acid, a vitamin that is known to be involved in quorum sensing and precursor of acetyl-CoA. Global metabolism of 8D-HYPOx cells showed some specific requirements and was globally shut down compared to 8D-NORMOx and STAT conditions. Mitochondrial analyses showed that the mitochondrial masse increased with mitochondria mostly depolarized in 8D-HYPOx compared to 8D-NORMox with an increased expression of mitochondrial genes. Proteomic and transcriptomic analyses of 8D-HYPOx revealed that the number of secreted proteins and transcripts detected also decreased compared to 8D-NORMOx and STAT, but proteome, secretome and transcriptome harbored specific profiles that are engaged as soon as four days of incubation. Importantly, acetyl-CoA and fatty acid pathway involving mitochondria is required for the generation and viability maintenance of VBNC. All together, these data show that we were able to generate for the first time VBNC phenotype in Cryptococcocus neoformans. This VBNC state is associated with a reduced and specific metabolism that should be further studied to understand dormancy/quiescence in this organism.

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Genetic determinants that permit growth without the core septin Cdc12 in Cryptococcus neoformans

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