Search Results (50)

This study provides the first comprehensive genome-wide identification and characterization of the SWEET gene family in yam (Dioscorea rotundata), integrating structural bioinformatics, gene expression profiling, and functional validation to explore its roles in sucrose transport and tuber development. A total of 19 SWEET genes were identified and predicted to localize to the plasma membrane, and they showed high phylogenetic conservation with Arabidopsis thaliana, suggesting conserved functions in sugar distribution. Yeast substrate assays revealed that DrSWEET6 and DrSWEET12 are capable of transporting both hexose and sucrose across the plasma membrane, with their expression predominantly observed in the tuber, implicating their involvement in sucrose unloading. Expression profiling indicated high expression levels of the SWEET genes at the tuber apex, which progressively increased during tuber development, underscoring their critical roles in sucrose unloading, cell expansion, and biomass accumulation. These findings provide novel insights into the structural and functional mechanisms of the SWEET-mediated sucrose transport in yam, laying a solid foundation for future crop improvement strategies aiming to optimize sucrose distribution and enhance tuber yield and quality. Full article

Background: Abnormal sodium-dependent hexose reabsorption in the proximal tubule, accompanied by a functional decrease in sodium and water reabsorption under conditions of increased volemia, may be attributed to a dysfunction of primary transporters related to a genetic defect in the Na,K-ATPase gamma subunit. Methods: We examined two sisters, aged 6 and 8 years, who presented with hypercalciuria, glucosuria, fructosuria, galactosuria, and atypical proteinuria. Primary diabetes, galactosemia, and fructosemia were excluded, suggesting a defect in cellular hexose transport in the proximal tubule. We conducted tests on the family members to assess the impact of gradually increasing volemia, using a water-loading test, on tubular H⁺ transport and urinary excretion of calcium, citrate, endothelin-1 (ET-1), and atypical proteins. Whole-exome sequencing was performed in the affected patients to identify the genetic basis of this phenotype. Results: Extended investigations revealed a complex defect in tubular H⁺ transport, calcium and citrate handling, and atypical proteinuria, resulting from water load-driven overproduction of endothelin-1 (ET-1). Genetic analysis identified a heterozygous pathogenic variant, c.80G>A, p.(Arg27His), in the FXYD2 gene, which encodes the gamma subunit of sodium/potassium-transporting ATPase. Conclusions: Our findings provide evidence that a defect in FXYD2 (splice form a) leads to functional impairment of proximal tubular hexose reabsorption. This is the first report on the metabolic consequences of a pathogenic FXYD2 variant affecting the gamma subunit of sodium/potassium-transporting ATPase in humans. The genotype–phenotype correlation in two siblings with a sodium-dependent defect in fructose, galactose, and glucose renal reabsorption allowed us to characterize a disease with a distinct clinical course and biochemical profile, not previously reported in the medical literature or genetic databases. Analysis of this condition was crucial for the early introduction of reno-protective treatment aimed at slowing the progression of nephropathy and for risk assessment in family members, which was essential for genetic counseling. Full article

Potassium (K) is an essential mineral element that supports numerous plant processes, including photosynthesis, enzyme activation, osmoregulation, and nutrient balance. This study investigated how K deficiency impacts growth, physiological performance, and carbohydrate metabolism in ‘Granny Smith’ apple trees grafted onto M9 rootstock. The experimental material was cultivated hydroponically in a greenhouse under four K regimes, including 0.00, 0.75, 1.50, and 3.00 mM K, over 159 days. Deficiency symptoms such as chlorosis and necrosis were observed primarily in basal leaves. A reduced net photosynthetic rate in top and basal leaves was linked to a decreased stomatal conductance, thus limiting CO₂ uptake (stomatal limitations of photosynthesis). Photosynthetic pigments, including chlorophyll a, chlorophyll b, and carotenoids, were also significantly reduced in K-limited leaves. Furthermore, photochemical performance of PSII also declined under K deficiency, with lower electron transport rates, PSII efficiency, and photochemical quenching (non-stomatal limitations of photosynthesis). While the photosynthetic rate declined under K deficiency conditions, the carbohydrate metabolism remained relatively stable without significant variation in total, translocating, or non-translocating sugars. Notably, an increase in sucrose-to-hexose ratio under low K suggests changes in sugar partitioning and utilization. Biomass allocation was also affected, with a notable decrease in the shoot-to-root ratio, mainly due to increased dry weight of roots, likely reflecting an adaptive response to enhance K uptake. Our study provides valuable insights into sustainable K fertilization practices aiming to maximize photosynthetic capacity, pigment content, and biomass production. These findings emphasize the importance of considering rootstock/scion interactions in future research to enhance apple tree vigor and productivity. Full article

Coconut (Cocos nucifera L.) is an important agricultural commodity with substantial economic and nutritional value, widely used for various products, including coconut water. The sweetness is an important quality trait of coconut water, which is influenced by genetic and environmental factors. In this study, we utilized next-generation sequencing to identify genetic variations in the coconut genome associated with the sweetness of coconut water. Whole-genome resequencing of 49 coconut accessions, including diverse germplasm and an F₂ population of 81 individuals, revealed ~27 M SNPs and ~1.5 M InDels. Sugar content measured by °Bx was highly variable across all accessions tested, with dwarf varieties generally sweeter. A comprehensive analysis of the sugar profiles revealed that sucrose was the major sugar contributing to sweetness. Allele mining of the 148 genes involved in sugar metabolism and transport and genotype–phenotype association tests revealed two significant SNPs in the hexose carrier protein (Cnu01G018720) and sucrose synthase (Cnu09G011120) genes associated with the higher sugar content in both the germplasm and F₂ populations. This research provides valuable insights into the genetic basis of coconut sweetness and offers molecular markers for breeding programs aimed at improving coconut water quality. The identified variants can improve the selection process in breeding high-quality sweet coconut varieties and thus support the economic sustainability of coconut cultivation. Full article

The powdery mildew caused by Eeysiphe heraclei is a serious concern in Heracleum moellendorffii Hance. Therefore, exploring the mechanisms underlying sugar efflux from host cells to the fungus during the plant–fungus interaction showed great significance. The study successfully cloned HmSWEET8 and HmSTP1 genes based on RNA-seq technology. The complementation assays in yeast EBY.VW4000 found HmSWEET8 and HmSTP1 transporting hexose. Over-expressing or silencing HmSWEET8 in H. moellendorffii leaves increased or decreased powdery mildew susceptibility by changing glucose concentration in infective sites. Meanwhile, over-expressing HmSTP1 in H. moellendorffii leaves also increased powdery mildew susceptibility by elevating the glucose content of infective areas. Additionally, HmSTP1 expression was up-regulated obviously in HmSWEET8 over-expressed plants and inhibited significantly in HmSWEET8 silenced plants. Co-expressing HmSWEET8 and HmSTP1 genes significantly increased powdery mildew susceptibility compared with over-expressed HmSWEET8 or HmSTP1 plants alone. The results demonstrated that HmSTP1 may assist with HmSWEET8 to promote E. heraclei infection. Consequently, the infection caused by E. heraclei resulted in the activation of HmSWEET8, leading to an increased transfer of glucose to the apoplasmic spaces at the sites of infection, then, HmSTP1 facilitated the transport of glucose into host cells, promoting powdery mildew infection. Full article

Sugar transporters play important roles in controlling carbohydrate transport and are responsible for mediating the movement of sugars into cells in numerous organisms. In insects, sugar transporters not only play a role in sugar transport but may also act as receptors for virus entry and the accumulation of plant defense compounds. The brown planthopper, Nilaparvata lugens, inflicts damage on rice plants by feeding on their phloem sap, which is rich in sugars. In the present study, we identified 34 sugar transporters in N. lugens, which were classified into three subfamilies based on phylogenetic analysis. The motif numbers varied from seven to eleven, and motifs 2, 3, and 4 were identified in the functional domains of all 34 NlST proteins. Chromosome 1 was found to possess the highest number of NlST genes, harboring 15. The gut, salivary glands, fat body, and ovary were the different tissues enriched with NlST gene expression. The expression levels of NlST2, 3, 4, 7, 20, 27, 28, and 31 were higher in the gut than in the other tissues. When expressed in a Saccharomyces cerevisiae hexose transporter deletion mutant (strain EBY.VW4000), only ApST4 (previously characterized) and NlST4, 28, and 31 were found to transport glucose and fructose, resulting in functional rescue of the yeast mutant. These results provide valuable data for further studies on sugar transporters in N. lugens and lay a foundation for finding potential targets to control N. lugens. Full article

Hexose transporters (HXT) play a crucial role in the pathogenicity of Magnaporthe oryzae, serving not only as key facilitators for acquiring and transporting sugar nutrients to support pathogen development, but also as sugar sensors which receive transduction signals. The objective of this study is to investigate the impact of MoHXT1-3 on rice pathogenicity and hexose affinity. MoHXT1-3 deletion mutants were generated using CRISPR/Cas9 technology, and their affinity for hexose was evaluated through yeast complementation assays and electrophysiological experiments in Xenopus oocytes. The results suggest that MoHXT1 does not contribute to melanin formation or hexose transportation processes. Conversely, MoHXT2, despite displaying lower affinity towards the hexoses tested in comparison to MoHXT3, is likely to have a more substantial impact on pathogenicity. The analysis of the transcription profiles demonstrated that the deletion of MoHXT2 caused a decrease in the expression of MoHXT3, whereas the knockout of MoHXT3 resulted in an upregulation of MoHXT2 transcription. It is noteworthy that the MoHXT2^M145K variant displayed an incapacity to transport hexoses. This investigation into the functional differences in hexose transporters in Magnaporthe oryzae provides insights into potential advances in new strategies to target hexose transporters to combat rice blast by blocking carbon nutrient supply. Full article

Single-cell RNA sequencing (scRNAseq) is a crucial tool in kidney research. These technologies cluster cells based on transcriptome similarity, irrespective of the anatomical location and order within the nephron. Thus, a transcriptome cluster may obscure the heterogeneity of the cell population within a nephron segment. Elevated dietary fructose leads to salt-sensitive hypertension, in part, through fructose reabsorption in the proximal tubule (PT). However, the organization of the four known fructose transporters in apical PTs (SGLT4, SGLT5, GLUT5, and NaGLT1) remains poorly understood. We hypothesized that cells within each subsegment of the proximal tubule exhibit complex, heterogeneous fructose transporter expression patterns. To test this hypothesis, we analyzed rat kidney transcriptomes and proteomes from publicly available scRNAseq and tubule microdissection databases. We found that microdissected PT-S1 segments consist of 81% ± 12% cells with scRNAseq-derived transcriptional characteristics of S1, whereas PT-S2 express a mixture of 18% ± 9% S1, 58% ± 8% S2, and 19% ± 5% S3 transcripts, and PT-S3 consists of 75% ± 9% S3 transcripts. The expression of all four fructose transporters was detectable in all three PT segments, but key fructose transporters SGLT5 and GLUT5 progressively increased from S1 to S3, and both were significantly upregulated in S3 vs. S1/S2 (Slc5a10: 1.9 log2FC, p < 1 × 10⁻²⁹⁹; Scl2a5: 1.4 log2FC, p < 4 × 10⁻¹⁰⁵). A similar distribution was found in human kidneys. These data suggest that S3 is the primary site of fructose reabsorption in both humans and rats. Finally, because of the multiple scRNAseq transcriptional phenotypes found in each segment, our findings also imply that anatomical labels applied to scRNAseq clusters may be misleading. Full article

Pollen cells require large amounts of sugars from the anther to support their development, which is critical for plant sexual reproduction and crop yield. Sugars Will Eventually be Exported Transporters (SWEETs) have been shown to play an important role in the apoplasmic unloading of sugars from anther tissues into symplasmically isolated developing pollen cells and thereby affect the sugar supply for pollen development. However, among the 17 CsSWEET genes identified in the cucumber (Cucumis sativus L.) genome, the CsSWEET gene involved in this process has not been identified. Here, a member of the SWEET gene family, CsSWEET5a, was identified and characterized. The quantitative real-time PCR and β-glucuronidase expression analysis revealed that CsSWEET5a is highly expressed in the anthers and pollen cells of male cucumber flowers from the microsporocyte stage (stage 9) to the mature pollen stage (stage 12). Its subcellular localization indicated that the CsSWEET5a protein is localized to the plasma membrane. The heterologous expression assays in yeast demonstrated that CsSWEET5a encodes a hexose transporter that can complement both glucose and fructose transport deficiencies. CsSWEET5a can significantly rescue the pollen viability and fertility of atsweet8 mutant Arabidopsis plants. The possible role of CsSWEET5a in supplying hexose to developing pollen cells via the apoplast is also discussed. Full article

Sugar transport from the source leaf to the sink organ is critical for seed development and crop yield, as well as for responding to abiotic stress. SWEETs (sugar will eventually be exported transporters) mediate sugar efflux into the reproductive sink and are therefore considered key candidate proteins for sugar unloading during seed development. However, the specific mechanism underlying the sugar unloading to seeds in Camellia oleifera remains elusive. Here, we identified a SWEET gene named CoSWEET10, which belongs to Clade III and has high expression levels in the seeds of C. oleifera. CoSWEET10 is a plasma membrane-localized protein. The complementation assay of CoSWEET10 in SUSY7/ura3 and EBY.VW4000 yeast strains showed that CoSWEET10 has the ability to transport sucrose, glucose, and fructose. Through the C. oleifera seeds in vitro culture, we found that the expression of CoSWEET10 can be induced by hexose and sucrose, and especially glucose. By generating the restoration lines of CoSWEET10 in Arabidopsis atsweet10, we found that CoSWEET10 restored the seed defect phenotype of the mutant by regulating soluble sugar accumulation and increased plant drought tolerance. Collectively, our study demonstrates that CoSWEET10 plays a dual role in promoting seed development and enhancing plant drought resistance as a sucrose and hexose transporter. Full article

As a starchy and edible tropical plant, cassava (Manihot esculenta Crantz) has been widely used as an industrial raw material and a dietary source. However, the metabolomic and genetic differences in specific germplasms of cassava storage root were unclear. In this study, two specific germplasms, M. esculenta Crantz cv. sugar cassava GPMS0991L and M. esculenta Crantz cv. pink cassava BRA117315, were used as research materials. Results showed that sugar cassava GPMS0991L was rich in glucose and fructose, whereas pink cassava BRA117315 was rich in starch and sucrose. Metabolomic and transcriptomic analysis indicated that sucrose and starch metabolism had significantly changing metabolites enrichment and the highest degree of differential expression genes, respectively. Sugar transport in storage roots may contribute to the activities of sugar, which will eventually be exported to transporters (SWEETs), such as (MeSWEET1a, MeSWEET2b, MeSWEET4, MeSWEET5, MeSWEET10b, and MeSWEET17c), which transport hexose to plant cells. The expression level of genes involved in starch biosynthesis and metabolism were altered, which may result in starch accumulation. These results provide a theoretical basis for sugar transport and starch accumulation and may be useful in improving the quality of tuberous crops and increasing yield. Full article

Magnesium (Mg) is critical for agricultural production and human health. The wax gourd yield was greatly affected by Mg fertilizer and it serves as an excellent crop to study Mg functioning in sink growth; however, as a Cucurbitaceae plant which is called a raffinose family oligosaccharides (RFOs)-transporting plant, its adaptive mechanism of photoassimilates transportation and distribution to Mg nutrients remains unknown. Herein, we used two Mg treatments (+Mg 90 kg ha⁻¹; CK as control 0 kg ha⁻¹) to observe the effects of Mg on the photoassimilates status in the leaves, phloem sap and fruit of wax gourd grown across the entire growth stage under a field condition. For the first time, we confirmed that stachyose and raffinose, which accounted for 54.9–78.0% of the total carbohydrates across the whole growth phase in the phloem sap, were the most predominant sugars used for the long-distance transport of wax gourds. They were strongly increased by Mg application which started from the seedling stage to the end of growing season. This response was earlier and more dramatic than the over-accumulation of sucrose in leaves regardless of positions. Hexoses (glucose plus fructose) were the main soluble sugars in the source leaves as well as in the mesocarp tissues, and their responses to Mg varied with temporal and spatial differences. The difference in the sugar status in the leaves between the upper, middle and lower positions is closely related to the concentration of Mg ions. Compared with Mg deficiency (CK), Mg application stimulated sugar accumulation in the leaves at the seedling and flowering stages by 10.6–24.5%. On the contrary, after fruit set, Mg supplementation significantly reduced the soluble sugar concentration in leaves by 33.5–67.9%. Mg treatment also spiked the fructose and glucose in fruit at the fruit expansion stage by 26.7% and 16.4%, respectively. Taken together, our results showed that Mg tailors the carbohydrate status in the source (leaves), flow (phloem sap) and sink (mesocarp tissues) in wax gourds, especially during the fruit growth period. The lower stachyose in the phloem at the beginning of fruit setting may be an early indication of a curtailed sink process in wax gourds grown in Mg deficient soil. Full article

The solvent-producing bacterium Clostridium acetobutylicum is able to grow on a variety of carbohydrates. The main hexose transport system is the phosphoenolpyruvate-dependent phosphotransferase system (PTS). When the gene glcG that encodes the glucose transporter was inactivated, the resulting mutant glcG::int(1224) grew as well as the wild type, yet its glucose consumption was reduced by 17% in a batch fermentation. Transcriptomics analysis of the phosphate-limited continuous cultures showed that the cellobiose transporter GlcCE was highly up-regulated in the mutant glcG::int(1224). The glcCE mutation did not affect growth and even consumed slightly more glucose during solventogenesis growth compared to wild type, indicating that GlcG is the primary glucose-specific PTS. Poor growth of the double mutant glcG::int(1224)-glcCE::int(193) further revealed that GlcCE was the secondary glucose PTS and that there must be other PTSs capable of glucose uptake. The observations obtained in this study provided a promising foundation to understand glucose transport in C. acetobutylicum. Full article

Microbial metabolism is strongly dependent on the environmental conditions. While these can be well controlled under laboratory conditions, large-scale bioreactors are characterized by inhomogeneities and consequently dynamic conditions for the organisms. How Saccharomyces cerevisiae response to frequent perturbations in industrial bioreactors is still not understood mechanistically. To study the adjustments to prolonged dynamic conditions, we used published repeated substrate perturbation regime experimental data, extended it with proteomic measurements and used both for modelling approaches. Multiple types of data were combined; including quantitative metabolome, ¹³C enrichment and flux quantification data. Kinetic metabolic modelling was applied to study the relevant intracellular metabolic response dynamics. An existing model of yeast central carbon metabolism was extended, and different subsets of enzymatic kinetic constants were estimated. A novel parameter estimation pipeline based on combinatorial enzyme selection supplemented by regularization was developed to identify and predict the minimum enzyme and parameter adjustments from steady-state to dynamic substrate conditions. This approach predicted proteomic changes in hexose transport and phosphorylation reactions, which were additionally confirmed by proteome measurements. Nevertheless, the modelling also hints at a yet unknown kinetic or regulation phenomenon. Some intracellular fluxes could not be reproduced by mechanistic rate laws, including hexose transport and intracellular trehalase activity during substrate perturbation cycles. Full article

Fluorine-18 labeled 6-fluoro-6-deoxy-D-fructose (6-[¹⁸F]FDF) targets the fructose-preferred facilitative hexose transporter GLUT5, which is expressed predominantly in brain microglia and activated in response to inflammatory stimuli. We hypothesize that 6-[¹⁸F]FDF will specifically image microglia following neuroinflammatory insult. 6-[¹⁸F]FDF and, for comparison, [¹⁸F]FDG were evaluated in unilateral intra-striatal lipopolysaccharide (LPS)-injected male and female rats (50 µg/animal) by longitudinal dynamic PET imaging in vivo. In LPS-injected rats, increased accumulation of 6-[¹⁸F]FDF was observed at 48 h post-LPS injection, with plateaued uptake (60–120 min) that was significantly higher in the ipsilateral vs. contralateral striatum (0.985 ± 0.047 and 0.819 ± 0.033 SUV, respectively; p = 0.002, n = 4M/3F). The ipsilateral–contralateral difference in striatal 6-[¹⁸F]FDF uptake expressed as binding potential (BP_SRTM) peaked at 48 h (0.19 ± 0.11) and was significantly decreased at one and two weeks. In contrast, increased [¹⁸F]FDG uptake in the ipsilateral striatum was highest at one week post-LPS injection (BP_SRTM = 0.25 ± 0.06, n = 4M). Iba-1 and GFAP immunohistochemistry confirmed LPS-induced activation of microglia and astrocytes, respectively, in ipsilateral striatum. This proof-of-concept study revealed an early response of 6-[¹⁸F]FDF to neuroinflammatory stimuli in rat brain. 6-[¹⁸F]FDF represents a potential PET radiotracer for imaging microglial GLUT5 density in brain with applications in neuroinflammatory and neurodegenerative diseases. Full article