A Novel High-Affinity Sucrose Transporter Is Required for Virulence of the Plant Pathogen Ustilago maydis

Abstract

A novel, high-affinity sucrose transporter identified in the plasma membrane of the plant pathogen Ustilago maydis is essential for fungal virulence and successful infection of maize.

A model ofUstilago maydisleaf tumor metabolism

“…2) and (3) feeding of U. maydis, which will most likely proceed via the high affinity sucrose transporter SRT1 that can outcompete host sucrose transporters based on its low K M for sucrose and will enable the pathogen to retrieve most of the sucrose. 7 Labeling of tumors and control leaves with 14 CO 2 showed that there is an increased pool of carbon in TCA cycle intermediates and amino acids, as more radioactivity remained in the organic acid and the cationic (AA) fraction in tumors articLe addeNdum articLe addeNdum reduced nitrogen into the biosynthesis of other amino acids or nucleobases in tumor tissue.…”

Organic acid production in Aspergillus niger and other filamentous fungi

“…This fact, plus additional insights observed at genomic, transcriptomic and proteomic level gave strong indications that RhtA acts as a specific transporter for L-rhamnose, but did not provide direct evidence. To assay transport capacity and quantify uptake kinetics, radiolabeled sugar uptake experiments can be performed with the mentioned yeast strain (Colabardini et al, 2014;dos Reis et al, 2013;Leandro et al, 2013;Sloothaak et al, 2015;Subtil and Boles, 2011;Wahl et al, 2010). This approach was followed in the present study as a final step to prove the ability of RhtA to transport L-rhamnose.…”

“…Similar phenotype analyses performed in filamentous fungi, where different sugar transporter mutant strains were studied, produced disparate results. In some cases, an altered growth phenotype could not be detected in plate assays containing the transporter's specific substrate (Forment et al, 2006(Forment et al, , 2014Vankuyk PA et al, 2004;Wahl et al, 2010), which is probably due to overlapping substrate specificities. In this regard, the most notorious case corresponds to S.…”

“…Regarding the sucrose transport by both transporters, since the EBY.VW4000 strain encodes an extracellular invertase (Wahl et al, 2010), it is unknown if the transported substrate was sucrose or glucose in the case of MstG, and sucrose, glucose or fructose in the case of MstH. These results indicated that MstG and…”

“…These yeast mutant strains, unable to grow on glucose, fructose, mannose and galactose as a single carbon source, have also subsequently been used as tools for the functional characterisation of sugar transporters from other fungal species (Colabardini et al, 2014;dos Reis et al, 2013;Du et al, 2010;Leandro et al, 2013;Polidori et al, 2007;Saloheimo et al, 2007;Vankuyk PA et al, 2004;Wahl et al, 2010) In contrast to S. cerevisiae, the only functionally validated sugar transporters in A. niger are the recently identified D-galacturonic acid transporter GatA (Martens-Uzunova and Schaap, 2008;Sloothaak et al, 2014), two fructose transporters (Coelho et al, 2013) and the high-affinity sugar/H + symporter MstA (Vankuyk PA et al, 2004). Furthermore, transcriptional data for the A. niger mstC gene suggests that it encodes a low-affinity glucose transporter (Jørgensen et al, 2007), but no experimental data supporting its role as a functional sugar transporter is publicly available.…”