The fungal UmSrt1 and transporters battle for maize ZmSUT1 sucrose plant sugar resources^FA

• Published in: 植物学报：英文版 2017, Vol.59 (6), p.422-435
• Main Author: Anke Wittek Ingo Dreyer Khaled A.S. AI-Rasheid Norbert Sauer Rainer Hedrich Dietmar Geiger
• Format: Article
• Language: English
• Subjects: 战斗; 植物资源; 玉米; 真菌; 糖类; 蔗糖; 转运
• ISSN: 1672-9072; 1744-7909

The biotrophic fungus Ustilago maydis causes corn smut disease, inducing tumor formation in its host Zea mays. Upon infection, the fungal hyphae invaginate the plasma membrane of infected maize ceils, establishing an interface where pathogen and host are separated only by their plasma membranes. At this interface the fungal and maize sucrose transporters, UmSrtl and ZmSUT1, compete for extracellular sucrose in the corn smut/maize pathos- ystem. Here we biophysically characterized ZmSUT1 and UmSrtl in Xenopus oocytes with respect to their voltage-, pH- and substrate-dependence and determined affinities toward protons and sucrose. In contrast to ZmSUT% UmSrtl has a high affinity for sucrose and is relatively pH- and voltage-independent. Using these quantitative parameters, we developed a mathematical model to simulate the competition for extracellular sucrose at the contact zone between the fungus and the host plant. This approach revealed that UmSrtl exploits the apoplastic sucrose resource, which forces the plant transporter into a sucrose export mode providing the fungus with sugar from the phloem. Importantly, the high sucrose concen- tration in the phloem appeared disadvantageous for the ZmSUT1 preventing sucrose recovery from the apoplastic space in the fungus/plant interface.