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Light-dependent coordination of development and secondary metabolism in the filamentous fungus Aspergillus nidulans

Subject Area Metabolism, Biochemistry and Genetics of Microorganisms
Term from 2020 to 2024
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 434377338
 
Final Report Year 2025

Final Report Abstract

Fungal development is affected by external signals including light, which promotes in Aspergillus nidulans enhanced asexual spore formation to disperse asexual conidia into the air. Darkness and a low oxygen to carbon dioxide ratio promote sexual development resulting in closed sexual fruiting bodies as resting structures in the soil with sexual ascospores. Asexual and sexual development are linked to the production of distinct and different secondary metabolites, which are also affected by the presence of other organisms in the environment. Hülle cells are a specific Aspergillus cell type of specialized multinuclear cells, which nurse and protect the sexual fruiting bodies of Aspergillus nidulans. The fungal-specific velvet domain proteins coordinate development to the appropriate secondary metabolism. Velvet domain proteins can form homo- and heterodimers with different functions in development and are monitored by the cellular protein stability control. In the last funding period we have shown, that velvet factor controlled Hülle cells of A. nidulans with nuclear storage and developmental backup functions are reminiscent of multipotent stem cells. We have identified various secondary metabolites of Hülle cells, which require the velvet regulators for their synthesis. These metabolites mediate protection of fungal reproductive and overwintering structures against fungivorous animals. As response to the presence of glycopetide-producing Streptomycetes bacteria, A. nidulans produces antibacterial ironchelating tropolones. Nuclear F-box proteins control substrate stability and subcellular location of regulatory proteins to organize fungal development and to anticipate stress. F-box proteins are receptors of the cell to label proteins for degradation by the 26S proteasome. The exchange of F-box receptors of SCFs requires the COP9 signalosome. Fungal COP9 signalosome assembly requires connection of two trimeric intermediates for integration of intrinsic deneddylase activity. A molecular circuit between A. nidulans transcription factors MsnA and VelB coordinates fungal stress and developmental responses. Induction of Aspergillus fumigatus zinc cluster transcription factor OdrA/Mdu2 provides combined cellular responses for oxidative stress protection and multiple antifungal drug tolerances.

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