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Iron uptake in Ustilago maydis: tracking the iron path
1Department of Plant Pathology and Microbiology and The Otto Warburg Center for Agricultural Biotechnology, The Hebrew University of Jerusalem, Israel.
Abstract:
In this study, we monitored and compared the uptake of iron in the fungus Ustilago maydis by using biomimetic siderophore analogs of ferrichrome, the fungal native siderophore, and ferrioxamine B (FOB), a xenosiderophore. Ferrichrome-iron was taken up at a higher rate than FOB-iron. Unlike ferrichrome-mediated uptake, FOB-mediated iron transport involved an extracellular reduction mechanism. By using fluorescently labeled siderophore analogs, we monitored the time course, as well as the localization, of iron uptake processes within the fungal cells. A fluorescently labeled ferrichrome analog, B9-lissamine rhodamine B, which does not exhibit fluorescence quenching upon iron binding, was used to monitor the entry of the compounds into the fungal cells. The fluorescence was found intracellularly 4 h after the application and later was found concentrated in two to three vesicles within each cell. The fluorescence of the fluorescently labeled FOB analog CAT18, which is quenched by iron, was visualized around the cell membrane after 4 h of incubation with the ferrated (nonfluorescent) compounds. This fluorescence intensity increased with time, demonstrating fungal iron uptake from the siderophores, which remained extracellular. We here introduce the use of fluorescent biomimetic siderophores as tools to directly track and discriminate between different pathways of iron uptake in cells.
Insights
Researchers tracked iron uptake in Ustilago maydis using fluorescent siderophore analogs. They found distinct uptake pathways for native ferrichrome and foreign ferrioxamine B (FOB), revealing new insights into fungal iron assimilation.
Area of Science:
- Mycology
- Biochemistry
- Cell Biology
Background:
- Fungi require iron for growth and survival.
- Siderophores are high-affinity iron-chelating compounds crucial for iron acquisition.
- Ustilago maydis utilizes native siderophores and can potentially utilize xenosiderophores.
Purpose of the Study:
- To compare the iron uptake rates and mechanisms of ferrichrome and ferrioxamine B (FOB) in Ustilago maydis.
- To visualize and localize iron uptake processes using fluorescently labeled siderophore analogs.
- To introduce fluorescent biomimetic siderophores as tools for studying cellular iron transport.
Main Methods:
- Utilized biomimetic siderophore analogs of ferrichrome and ferrioxamine B (FOB).
- Employed fluorescently labeled siderophore analogs (B9-lissamine rhodamine B and CAT18) to track iron uptake.
- Monitored time course and intracellular localization of siderophore-iron complexes using fluorescence microscopy.
Main Results:
- Ferrichrome-iron was taken up at a higher rate than FOB-iron.
- FOB-mediated iron transport involved an extracellular reduction mechanism, unlike ferrichrome uptake.
- Fluorescence from the ferrichrome analog was observed intracellularly within vesicles, while FOB fluorescence remained extracellular, indicating iron uptake.
Conclusions:
- Fluorescent biomimetic siderophores are effective tools for directly tracking and differentiating cellular iron uptake pathways.
- Ustilago maydis exhibits distinct mechanisms for acquiring iron via native and foreign siderophores.
- The study provides novel insights into the regulation and localization of fungal iron assimilation.
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