Gliotoxin, a member of the epipolythiodioxopiperazine (ETP) class of toxins, is important to virulence in certain host models. Most genes involved in gliotoxin production and transport are located on a gene cluster, which is co-transcribed. Deletion of an essential gene within the gliotoxin biosynthetic pathway, gliP, led to a lack of gliotoxin production within A. fumigatus, as well as a significant reduction in virulence in a steroid treated host. Reduced virulence was a result of the presence of neutrophils within the host, as other labs using neutropenic mouse models did not see this trend. In microarray studies, gliA, the gliotoxin efflux pump, is induced over 30-fold in the presence of neutrophils. Growth of A. fumigatus in medium containing sodium nitrate also significantly induces expression of gliA. Although many studies have been done to elucidate the effects of gliotoxin on host cells, little is known about the expression of the gliotoxin cluster. To identify cis-acting regulatory elements in the gliA promoter, we examined expression from promoter deletion mutants fused to lacZ. Several positive and negative regulatory elements were identified that altered expression in a nitrogen source dependent manner. Using a gliA promoter lacZ fusion reporter construct, we screened for activators of gliA expression and identified candidate plasmids that activate the reporter. W e are conducting additional experiments to investigate this regulation. Elucidating the genes that are responsible for the regulation of gliA will lead to a greater understanding of gliotoxin synthesis and transport, which is important to the pathogenesis of A. fumigatus.
Full conference title:
7th International Aspergillus Meeting
- Asperfest 7 (2010)