Abstract
All plant-interacting microbes must acquire metabolites from their hosts to satisfy nutritional demands for growth. With carbon being crucial for all organisms, sufficient acquisition of sugars from plants is a cardinal task of plant pathogens for successful invasion. Blocking access to host sugars seems to be a promising strategy to control plant diseases. Plant sugar retrieval strengthens plant resistance to pathogens (Yamada et al., 2016). However, it is difficult to discriminate if this is a result of blocking the pathogen’s access to sugar, or a disturbance in sugar-mediated signalling in plants (Milne et al., 2019; Moore et al., 2015). Since the identification of UfHXT1 provided the first evidence of sugar uptake in rust fungi (Voegele et al., 2001), many sugar transporters have been identified from different pathogenic fungi (Saitoh et al., 2014; Schuler et al., 2015). However, the effects of sugar starvation on pathogen growth, development and pathogenicity are still unclear. Puccinia striiformis f.sp. tritici (Pst) is the causal agent of stripe (yellow) rust, which threatens global wheat production severely. So far, control of Pst mostly relies on the deployment of resistant cultivars carrying specific resistance (R) genes, and the use of chemical fungicides. However, novel, sustainable ways to control Pst are desperately needed. Recently, hexoses were shown to be the major form of sugars utilized by this obligate biotrophic fungus (Chang et al., 2017). In this study, we cloned the hexose transporter gene PsHXT1, which is the only one highly induced during Pst infection (Zheng et al., 2013). Further analysis of PsHXT1/PsHXT1 revealed typical characteristics of a major facilitator superfamily (MFS) symporter with 12 membrane-spanning segments (Figure 1a). Intraspecies polymorphism of PsHXT1 seems to be fairly low, as all eleven compared Pst genomes show a similarity of greater 99% at the nucleotide level (Figure 1b). While the interspecies variation ranges between 83% and 91% among closely related species, PsHXT1 is clearly different from other rust fungal glucose transporters characterized so far. It only shares 26% similarity with UfHXT1 (Figure 1c). As genes involved in sugar acquisition are much more conserved compared with effectors (Oliva and Quibod, 2017), these genes/proteins might represent promising targets for novel ways to control plant diseases. Transcript levels of PsHXT1 during Pst infection were analysed by qRT-PCR for the complete invasion process (Figure 1d). Transcript levels of PsHXT1 increased from 12 h post-inoculation (hpi), when primary infection starts with substomatal vesicle formation, and increased continuously to reach a maximum at 168 hpi, when branched hyphae develop and more haustoria are formed. Thereafter, transcript levels sharply decrease to a very low level. This result indicates that PsHXT1 is indispensable for establishing the Pst–wheat interaction. In order to determine the subcellular localization of PsHXT1, a PsHXT1-GFP fusion protein was generated and expressed in yeast. PsHXT1 was shown to localize to the plasma membrane (Figure 1e). The subcellular localization of PsHXT1 was further analysed by expression in Nicotiana benthamiana (Figure 1f). Both plasmolysis and staining with the membrane marker SynaptoRed™ C2 (FM4-64) confirmed a plasma membrane localization of PsHXT1. Based on a similar subcellular localization, PsHXT1 could function as a transporter as UfHXT1 (Voegele et al., 2001). In order to identify the biochemical characteristics of PsHXT1, PsHXT1 was expressed in the Saccharomyces cerevisiae mutant strain EBY.VW4000, which lacks all 20 hexose transporters identified. PsHXT1 was shown to exhibit a substrate preference of glucose (Figure 1g). The Km of PsHXT1 was 59 ± 12 μm, and the Vmax was 7.75 ± 2.33 nm under optimal conditions (Figure 1h). The optimum pH of PsHXT1 is about 5.5, but transport activity retained a high level within the pH range from 4 to 7. Two different protonophores, carbonyl cyanide m-chlorophenylhydrazone (CCCP) and 2,4-dinitrophenol (DNP), were both able to inhibit the activity of PsHXT1. The SH group inhibitor, p-chloromercuribenzene sulphonate (pCMBS), had no effect on PsHXT1 activity. Competition experiments confirmed that PsHXT1 has a high affinity for glucose only. All these results indicate that PsHXT1 is a glucose–proton symporter. In order to determine the biological function of PsHXT1 in a Pst–wheat interaction, PsHXT1 was silenced by barley stripe mosaic virus (BSMV)-mediated host-induced gene silencing (HIGS). Two independent fragments (PsHXT1-1as and PsHXT1-2as) were chosen to silence PsHXT1, and PsINVas served as a positive control (Chang et al., 2017). Disease phenotypes of Pst infection were observed for 14 days. Disease phenotypes decreased on plants treated with either BSMV:PsHXT1-1as or BSMV:PsHXT1-2as (Figure 1i). Statistical analysis of the quantity of uredia on infected leaves further supports the differences in disease phenotypes. In addition, the biomass ratio indicates that the biomass of Pst in leaves treated with either BSMV:PsHXT1-1as or BSMV:PsHXT1-2as decreased significantly compared with leaves treated with BSMV:00. Development and growth of Pst were examined by histological observation in PsHXT1-silenced plants (Figure 1j). At 24 hpi, Pst formed more branches, and inflated substomatal vesicles could be observed in nearly 30% of the cases. This indicates that there might be problems with the establishment of the Pst–wheat interaction with PsHXT1-silenced plants. At 48 hpi, hyphae showed abnormal development and exhibited high levels of malformation (in nearly 70% of the cases). At 120 hpi, the infection area of Pst was significantly decreased in PsHXT1-silenced plants. Taken together, these results indicate that silencing PsHXT1 restricts normal growth and development of Pst during the infection of wheat significantly, leading to a decrease in fungal biomass and disease symptoms. Combined with the former study on PsINV (Chang et al., 2017), it can be concluded that sugar starvation not only impairs growth and development of Pst, but also slows down pathogen proliferation. To our knowledge, this is the first in vivo evidence demonstrating that sugar starvation restricts both pathogen’s growth and virulence without a possible confusion with signalling effects. This opens new vistas for sugar starvation-mediated control of wheat stripe rust and suggests that blocking a pathogen’s sugar absorption could be a novel strategy to control disease with restricting pathogen’s growth and proliferation. Although most attention has been paid into seeking effectors and R genes, generating transgenic plants able to silence key transporters in the pathogen might be a future, sustainable alternative to conventional breeding efforts constantly introducing novel R gene combinations, which might easily be overcome. In addition, spraying dsRNA to silence key nutrient uptake elements in pathogens might provide another effective method to control plant diseases (Wang et al., 2016). The GenBank accession number of PsHXT1 is MT036379. This study was financially supported by the National Natural Science Foundation of China (31620103913), the National Key Research and Development Program of China (2016YFD0100602) and the Open Project of State Key Laboratory of Crop Stress Biology for Arid Areas (CSBAA2019011). The authors declare no conflict of interest. QC, ZK and JL designed the research. QC, XL and MY performed the experiments. QC, JG and PL analysed the data. QC, LH and RV wrote the manuscript.
Abstract from the paper’s OpenAlex record; open copy licensed cc-by-nc. Read at the source ↗
The text the model read, with the source record’s inline markup (italics, sub- and superscripts) rendered and its character entities decoded; quote offsets refer to the raw text.
Claims 20
Claim · model-written summary
PsHXT1 was cloned and was the only transporter highly induced during infection.
- Taxon
- wheat
Triticum aestivumt0 - Interactor
- Pste0pathogen
- Gene
- PsHXT1e0
- Outcome
- only one highly induced during Pst infectione0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“we cloned the hexose transporter gene PsHXT1, which is the only one highly induced during Pst infection”
t0“wheat stripe rust”
Claim · model-written summary
PsHXT1 has 12 membrane spanning segments characteristic of a symporter.
- Taxon
- wheatTriticum aestivumt0
- Gene
- PsHXT1e0
- Outcome
- major facilitator superfamily (MFS) symportere0
- Value
- 12 membrane-spanning segmentse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“PsHXT1/PsHXT1 revealed typical characteristics of a major facilitator superfamily (MFS) symporter with 12 membrane-spanning segments”
t0“wheat stripe rust”
Claim · model-written summary
PsHXT1 sequence similarity exceeded 99% across eleven Pst genomes.
- Taxon
- wheatTriticum aestivumt0
- Interactor
- Pste0pathogen
- Gene
- PsHXT1t1
- Outcome
- similaritye0
- Value
- greater 99%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“all eleven compared Pst genomes show a similarity of greater 99% at the nucleotide level”
t0“wheat stripe rust”
t1“PsHXT1”
Claim · model-written summary
PsHXT1 interspecies similarity ranged from 83% to 91%.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- interspecies variatione0
- Value
- between 83% and 91%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the interspecies variation ranges between 83% and 91% among closely related species”
t0“wheat stripe rust”
Claim · model-written summary
PsHXT1 shared 26% similarity with UfHXT1.
- Taxon
- wheatTriticum aestivumt0
- Gene
- UfHXT1e0
- Outcome
- similarity with UfHXT1e0
- Value
- 26%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“It only shares 26% similarity with UfHXT1”
t0“wheat stripe rust”
Claim · model-written summary
PsHXT1 transcript levels rose from 12 hpi to a maximum at 168 hpi and then sharply fell.
- Taxon
- wheatTriticum aestivumt0
- Gene
- PsHXT1e0
- Outcome
- Transcript levels of PsHXT1e0
- Direction
- increasede0
- Value
- 168 hpie0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Transcript levels of PsHXT1 increased from 12 h post-inoculation (hpi), when primary infection starts with substomatal vesicle formation, and increased continuously to reach a maximum at 168 hpi, when branched hyphae develop and more haustoria are formed. Thereafter, transcript levels sharply decrease to a very low level”
t0“wheat stripe rust”
Claim · model-written summary
PsHXT1 localized to the plasma membrane in yeast and Nicotiana benthamiana.
- Taxon
- Nicotiana benthamiana
Nicotiana benthamianae1 - Gene
- PsHXT1e0
- Outcome
- plasma membrane localizatione0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Both plasmolysis and staining with the membrane marker SynaptoRed™ C2 (FM4-64) confirmed a plasma membrane localization of PsHXT1”
e1“Nicotiana benthamiana”
Claim · model-written summary
PsHXT1 preferred glucose as a substrate.
- Taxon
- wheatTriticum aestivumt0
- Gene
- PsHXT1e0
- Outcome
- substrate preference of glucosee0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“PsHXT1 was shown to exhibit a substrate preference of glucose”
t0“wheat stripe rust”
Claim · model-written summary
PsHXT1 Km was 59 ± 12 μm.
- Taxon
- wheatTriticum aestivumt0
- Gene
- PsHXT1e0
- Outcome
- Km of PsHXT1e0
- Value
- 59 ± 12 μme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The Km of PsHXT1 was 59 ± 12 μm”
t0“wheat stripe rust”
Claim · model-written summary
PsHXT1 Vmax was 7.75 ± 2.33 nm.
- Taxon
- wheatTriticum aestivumt0
- Gene
- PsHXT1t1
- Outcome
- Vmaxe0
- Value
- 7.75 ± 2.33 nme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the Vmax was 7.75 ± 2.33 nm under optimal conditions”
t0“wheat stripe rust”
t1“PsHXT1”
Claim · model-written summary
PsHXT1 optimum pH was about 5.5 while activity remained high from pH 4 to 7.
- Taxon
- wheatTriticum aestivumt0
- Gene
- PsHXT1e0
- Outcome
- optimum pH of PsHXT1e0
- Value
- about 5.5e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The optimum pH of PsHXT1 is about 5.5, but transport activity retained a high level within the pH range from 4 to 7”
t0“wheat stripe rust”
Claim · model-written summary
CCCP and DNP each inhibited PsHXT1 activity.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- CCCPe0
- Outcome
- activity of PsHXT1e0
- Direction
- inhibite0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Two different protonophores, carbonyl cyanide m-chlorophenylhydrazone (CCCP) and 2,4-dinitrophenol (DNP), were both able to inhibit the activity of PsHXT1”
t0“wheat stripe rust”
Claim · model-written summary
pCMBS had no effect on PsHXT1 activity.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- pCMBSe0
- Outcome
- PsHXT1 activitye0
- Direction
- no effecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“p-chloromercuribenzene sulphonate (pCMBS), had no effect on PsHXT1 activity”
t0“wheat stripe rust”
Claim · model-written summary
Competition experiments showed high affinity for glucose only.
- Taxon
- wheatTriticum aestivumt0
- Gene
- PsHXT1e0
- Outcome
- high affinity for glucose onlye0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Competition experiments confirmed that PsHXT1 has a high affinity for glucose only”
t0“wheat stripe rust”
Claim · model-written summary
Silencing PsHXT1 reduced disease phenotypes.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- BSMV:PsHXT1-1ase0
- Gene
- PsHXT1e0
- Outcome
- Disease phenotypese0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Disease phenotypes decreased on plants treated with either BSMV:PsHXT1-1as or BSMV:PsHXT1-2as”
t0“wheat stripe rust”
Claim · model-written summary
Silencing PsHXT1 significantly reduced Pst biomass relative to BSMV:00.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- BSMV:PsHXT1-1ase0
- Interactor
- Pste0pathogen
- Outcome
- biomass of Pste0
- Direction
- decreasede0
- Comparator
- BSMV:00e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the biomass of Pst in leaves treated with either BSMV:PsHXT1-1as or BSMV:PsHXT1-2as decreased significantly compared with leaves treated with BSMV:00”
t0“wheat stripe rust”
Claim · model-written summary
At 24 hpi Pst formed more branches and inflated substomatal vesicles in nearly 30% of cases.
- Taxon
- wheatTriticum aestivumt0
- Interactor
- Pste0pathogen
- Outcome
- inflated substomatal vesiclese0
- Value
- nearly 30%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At 24 hpi, Pst formed more branches, and inflated substomatal vesicles could be observed in nearly 30% of the cases”
t0“wheat stripe rust”
Claim · model-written summary
At 48 hpi hyphae showed abnormal development in nearly 70% of cases.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- hyphae showed abnormal developmente0
- Value
- nearly 70%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At 48 hpi, hyphae showed abnormal development and exhibited high levels of malformation (in nearly 70% of the cases)”
t0“wheat stripe rust”
Claim · model-written summary
At 120 hpi Pst infection area significantly decreased in PsHXT1 silenced plants.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- PsHXT1-silenced plantse0
- Interactor
- Pste0pathogen
- Outcome
- infection area of Pste0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At 120 hpi, the infection area of Pst was significantly decreased in PsHXT1-silenced plants”
t0“wheat stripe rust”
Claim · model-written summary
Authors propose blocking pathogen sugar absorption as a disease control strategy.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- blocking a pathogen’s sugar absorptione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“blocking a pathogen’s sugar absorption could be a novel strategy to control disease with restricting pathogen’s growth and proliferation”
t0“wheat stripe rust”
The same questions in other papers
Hordeum vulgare · growth · Triticum aestivum (wheat)Positive and negative results
1 paper in the same direction as this paper · 6 in the opposite direction
- negative
- negative
- negative
4 papers more in this group
See all 8 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.