Sensitivity of transcription factor mutants of Aspergillus fumigatus to Congo Red

ABSTRACT: Inhibition of fungal growth by Congo Red (CR) has been known for a long time and claimed to be associated to a specific binding to fibrillar chains of β-1,3-glucans which blocks cell wall polysaccharide synthesis. It has also been suggested that the effect of CR could be pleiotropic, especially because of its oxido-reductive properties. One way to elucidate the mechanism of action of CR is to identify transcription factors (TF) which regulate the response to CR and interrogate their regulon. The analysis of TF mutants with differential sensitivity to CR would be also a way to identify new regulatory pathways involved in cell wall biosynthesis. During the investigation of the sensitivity to CR of a TF mutant library, several mutants either sensitive or resistant to CR were analysed . The morphology of the conidial germination was affected differently by CR in the parental strain and TF mutants. Abnormal distorted swollen conidia called Quasimodo cells were seen in presence of the CR. The size of the Quasimodo cells in the resistant mutants are bigger and adsorb more CR than the germinating conidia of the sensitive or parental strain. This is associated to a difference in permeability of the mutants. The clearing of the drug from the medium by the resistant strain was mainly responsible for the survival and later growth of some of resting conidia of these mutants which did not adsorb intracellularly the drug whereas in the sensitive mutants all conidia adsorbed the drug and were consequently killed. Although there are some modifications of the composition of the cell wall, a transcriptomic analysis of the mutant showed that CR affected many different pathways, including iron and calcium metabolism. Accordingly, the susceptibility to other cell wall drugs of the sensitive and the resistant TF mutants varied with the mutants and not always in connexion with their sensitivity to CR. Interestingly, a new paradoxical effect of the CR was discovered in the resistant mutant since the growth of one of them could be stimulated after recovering from the CR stress.

ORGANISM(S): Aspergillus fumigatus

PROVIDER: GSE140840 | GEO | 2021/04/26

REPOSITORIES: GEO