AcuM and AcuK: the global regulators controlling multiple cellular metabolisms in a dimorphic fungus Talaromyces marneffei
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Talaromycosis is a fungal infection caused by an opportunistic dimorphic fungus Talaromyces marneffei . During infection, T. marneffei resides inside phagosomes of human host macrophages where the fungus encounters nutrient scarcities and host-derived oxidative stressors. Previously, we showed that the deletion of acuK, a gene encoding Zn(2)Cys(6) transcription factor, caused a decreased ability for T. marneffei to defend against macrophages, as well as a growth impairment in T. marneffei on both low iron-containing medium and gluconeogenic substrate-containing medium. In this study, a paralogous gene acuM was deleted and characterized. The Δ acuM mutant showed similar defects with the Δ acuK mutant, suggesting their common role in gluconeogenesis and iron homeostasis. Unlike the pathogenic mold Aspergillus fumigatus , the Δ acuK and Δ acuM mutants unexpectedly exhibited normal siderophore production and did not show lower expression levels of genes involved in iron uptake and siderophore synthesis. To identify additional target genes of AcuK and AcuM, RNA-sequencing analysis was performed in the Δ acuK and Δ acuM strains growing in a synthetic dextrose medium with 1% glucose at 25 °C for 36 hours. Downregulated genes in both mutants participated in iron-consuming processes, especially in mitochondrial metabolism and anti-oxidative stress. Importantly, the Δ acuM mutant was sensitive to the oxidative stressors menadione and hydrogen peroxide while the Δ acuK mutant was sensitive to only hydrogen peroxide. The yeast form of both mutants demonstrated a more severe defect in antioxidant properties than the mold form. Moreover, ribosomal and ribosomal biogenesis genes were expressed at significantly lower levels in both mutants, suggesting that AcuK and AcuM could affect the protein translation process in T. marneffei . Our study highlighted the role of AcuK and AcuM as global regulators that control multiple cellular adaptations under various harsh environmental conditions during host infection. These transcription factors could be potentially exploited as therapeutic targets for the treatment of this neglected infectious disease.
AUTHOR SUMMARY
Talaromyces marneffei invades host macrophages to establish infection. Major stressors inside the macrophage compartments are nutrient deprivation and oxidative substances. Here, we demonstrated that AcuK and AcuM transcription factors are necessary for T. marneffei to grow under iron and glucose limitation, and to survive oxidative stress and macrophage killing. AcuK and AcuM regulate non-glucose carbon utilization via the transcriptional control of gluconeogenic genes. For iron homeostasis, the two proteins regulate the expression of genes involved in iron-utilization pathways. Lastly, the AcuK and AcuM play a role in oxidative stress response likely by regulating the expression of genes encoding antioxidant enzymes and alternative respiration enzymes. Thus, AcuK and AcuM control multiple cellular adaptations that allow T. marneffei to cope with major stressors occurring during macrophage infection. Since AcuK and AcuM are critical for cellular metabolism and macrophage engulfment, this new information could lead to a better understanding of host-pathogen interaction and could be ultimately developed into fungal-specific diagnostic tools and therapeutic agents.
