Although initially investigated for its antifungal properties, little is actually known about the effect of
gliotoxin on Aspergillus fumigatus and other fungi. We have observed that exposure of A. fumigatus to
exogenous gliotoxin (14 lg/ml), under gliotoxin-limited growth conditions, results in significant alteration
of the expression of 27 proteins (up- and down-regulated >1.9-fold; p < 0.05) including de novo
expression of Cu, Zn superoxide dismutase, up-regulated allergen Asp f3 expression and down-regulated
catalase and a peroxiredoxin levels. Significantly elevated glutathione GSH levels (p < 0.05), along with
concomitant resistance to diamide, were evident in A. fumigatus ∆gliT, lacking gliotoxin oxidoreductase,
a gliotoxin self-protection gene. Saccharomyces cerevisiae deletents (∆sod1 and ∆yap1) were hypersensitive
to exogenous gliotoxin, while ∆gsh1 was resistant. Significant gliotoxin-mediated (5 µg/ml) growth
inhibition (p < 0.001) of Aspergillus nidulans, Aspergillus terreus, Aspergillus niger, Cochliobolus heterostrophus
and Neurospora crassa was also observed. Growth of Aspergillus flavus, Fusarium graminearum and
Aspergillus oryzae was significantly inhibited (p < 0.001) at gliotoxin (10 lg/ml), indicating differential
gliotoxin sensitivity amongst fungi. Re-introduction of gliT into A. fumigatus DgliT, at a different locus
(ctsD; AFUA_4G07040, an aspartic protease), with selection on gliotoxin, facilitated deletion of ctsD without
use of additional antibiotic selection markers. Absence of ctsD expression was accompanied by restoration
of gliT expression, and resistance to gliotoxin. Thus, we propose gliT/gliotoxin as a useful
selection marker system for fungal transformation. Finally, we suggest incorporation of gliotoxin sensitivity
assays into all future fungal functional genomic studies
