Iron uptake in Ustilago maydis: tracking the iron path

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.