Unraveling the role of the antifungal peptide AnAFP in Aspergillus niger through a systems biology perspective

Antimicrobial peptides are ubiquitous across all life forms and they often serve as a first line of defense, protecting their host organisms from predators, intruders, or nutritional competitors. A notable example, AnAFP from Aspergillus niger, has recently demonstrated the potential for an additional, endogenous role. The expression profile of anafp suggests that it has a distinct function within axenic cultures and is active during a defined timeframe that coincides with carbon depletion. This expression pattern correlates with the activation of genes associated with autophagy, nutrient recycling, and development. Consequently, it has been suggested that AnAFP may operate as a cannibalistic toxin, promoting programmed cell death and contributing to the progression of development, ultimately ensuring the survival of a subpopulation of A. niger. To validate this hypothesis, anafp expression was put under the regulation of the doxycycline-responsive Tet-on gene switch. As a result, the titratable expression of anafp led to a reduced growth of A. niger in both shake flask and solid agar media when its expression was induced prematurely, which is prior to carbon depletion. Additionally, the results of this study provide first evidence that anafp transcript translation relies on the existence of regulatory sequences in the untranslated regions of its mRNA. Moreover, the expression of anafp in A. niger mycelia was examined for signs of autophagy and apoptosis, to determine whether the observed reduction in growth results from cell death. In line with this analysis, the subcellular distribution of AnAFP -eGFP was explored using live-cell confocal fluorescence microscopy, revealing compartmentalized translation of the fusion protein, which accumulates in the cell periphery and coincides with a sudden reduction in the hyphal diameter. Lastly, the transcriptomic response of anafp-overexpressing cells was compared to a non-induced phenotype after prolonged carbon starvation. Differentially expressed genes included the catabolism of carbohydrates, proteins, lipids and nucleobases; the activation of an array of transmembrane transporters; a reaction to reactive oxygen species presence and a widespread downregulation of developmental genes. This research, therefore, proposes a novel role for AnAFP, suggesting its intracellular involvement in nutrient mobilization, a role that extends far beyond its activity as an antifungal peptide.

Author dc:creator

• Starke, Stephan

Advisor dc:contributor.advisor

• Meyer, Vera

Licence dc:rights.uri

• https://creativecommons.org/licenses/by/4.0/

Language dc:language.iso

en

Identifier URI

https://doi.org/10.14279/depositonce-21002

OAI identifier oai:identifier

oai:depositonce.tu-berlin.de:11303/22201