PIP aquaporin pH-sensing is regulated by the length and charge of the C-terminal region.

Plant PIP aquaporins play a central role in controlling plant water status. The current structural model for PIP pH-gating states that the main pH sensor is located in loopD and that all the mobile cytosolic elements participate in a complex interaction network that ensures the closed structure. However, the precise participation of the last part of the C-terminal domain (CT) in PIP pH gating remains unknown. This last part has not been resolved in PIP crystal structures and is a key difference between PIP1 and PIP2 paralogues. Here, by a combined experimental and computational approach, we provide data about the role of CT in pH gating of Beta vulgaris PIP. We demonstrate that the length of CT and the positive charge located among its last residues modulate the pH at which the open/closed transition occurs. We also postulate a molecular-based mechanism for the differential pH sensing in PIP homo- or heterotetramers by performing atomistic molecular dynamics simulations (MDS) on complete models of PIP tetramers. Our findings show that the last part of CT can affect the environment of loopD pH sensors in the closed state. Results presented herein contribute to the understanding of how the characteristics of CT in PIP channels play a crucial role in determining the pH at which water transport through these channels is blocked, highlighting the relevance of the differentially conserved very last residues in PIP1 and PIP2 paralogues.

Reducing the Periplasmic Glutathione Content Makes Escherichia coli Resistant to Trimethoprim and Other Antimicrobial Drugs.

Although glutathione (GSH) has been shown to influence the antimicrobial effects of many kinds of antibiotics, little is known about its role in relation to trimethoprim (TMP), a widely used antifolate. In this study, several genes related to glutathione metabolism were deleted in different Escherichia coli strains (i.e., O157:H7 and ATCC 25922), and their effects on susceptibility to TMP were tested. The results showed that deleting gshA, gshB, grxA, and cydD caused TMP resistance, and deleting cydD also caused resistance to other drugs. Meanwhile, deleting gshA, grxA, and cydD resulted in a significant decrease of the periplasmic glutathione content. Supplementing exogenous GSH or further deleting glutathione importer genes (gsiB and ggt) restored TMP sensitivity to ΔcydD. Subsequently, the results of quantitative-reverse transcription PCR experiments showed that expression levels of acrA, acrB, and tolC were significantly upregulated in both ΔgrxA and ΔcydD. Correspondingly, deleting cydD led to a decreased accumulation of TMP within bacterial cells, and further deleting acrA, acrB, or tolC restored TMP sensitivity to ΔcydD. Inactivation of CpxR and SoxS, two transcriptional factors that modulate the transcription of acrAB-tolC, restored TMP sensitivity to ΔcydD. Furthermore, mutations of gshA, gshB, grxA, cydC, and cydD are highly prevalent in E. coli clinical strains. Collectively, these data suggest that reducing the periplasmic glutathione content of E. coli leads to increased expression of acrAB-tolC with the involvement of CpxR and SoxS, ultimately causing drug resistance. To the best of our knowledge, this is the first report showing a linkage between periplasmic GSH and drug resistance in bacteria. IMPORTANCE After being used extensively for decades, trimethoprim still remains one of the key accessible antimicrobials recommended by the World Health Organization. A better understanding of the mechanisms of resistance would be beneficial for the future utilization of this drug. It has been shown that the AcrAB-TolC efflux pump is associated with trimethoprim resistance in E. coli clinical strains. In this study, we show that E. coli can sense the periplasmic glutathione content with the involvement of the CpxAR two-component system. As a result, reducing the periplasmic glutathione content leads to increased expression of acrA, acrB, and tolC via CpxR and SoxS, causing resistance to antimicrobials, including trimethoprim. Meanwhile, mutations in the genes responsible for periplasmic glutathione content maintenance are highly prevalent in E. coli clinical isolates, indicating a potential correlation of the periplasmic glutathione content and clinical antimicrobial resistance, which merits further investigation.

Plant mitochondria import DNA via alternative membrane complexes involving various VDAC isoforms.

Mitochondria possess transport mechanisms for import of RNA and DNA. Based on import into isolated Solanum tuberosum mitochondria in the presence of competitors, inhibitors or effectors, we show that DNA fragments of different size classes are taken up into plant organelles through distinct channels. Alternative channels can also be activated according to the amount of DNA substrate of a given size class. Analyses of Arabidopsis thaliana knockout lines pointed out a differential involvement of individual voltage-dependent anion channel (VDAC) isoforms in the formation of alternative channels. We propose several outer and inner membrane proteins as VDAC partners in these pathways.

SIRT1-dependent restoration of NAD+ homeostasis after increased extracellular NAD+ exposure.

In the last several years, NAD+ supplementation has emerged as an innovative and safe therapeutic strategy for a wide spectrum of disorders, including diabetes and neuropathy. However, critical questions remain as to how NAD+ and its precursors are taken up by cells, as well as the effects of long-lasting intracellular NAD+ (iNAD+) increases. Here, we investigated the kinetics of iNAD+ levels in different cell types challenged with prolonged exposure to extracellular NAD+ (eNAD+). Surprisingly, we found that after the initial increase, iNAD+ contents decreased back to control levels (iNAD+ resetting). Focusing our attention on HeLa cells, we found that oxygen and ATP consumption occurred with similar temporal kinetics after eNAD+ exposure. Using [3H]NAD+ and [14C]NAD+, we determined that NAD+ resetting was not due to increased dinucleotide extrusion but rather due to reduced uptake of cleaved NAD+ products. Indeed, eNAD+ exposure reduced the expression of the ecto-5'-nucleotidase CD73, the nicotinamide adenine mononucleotide transporter solute carrier family 12 member 8, and the nicotinamide riboside kinase. Interestingly, silencing the NAD+-sensor enzyme sirtuin 1 prevented eNAD+-dependent transcriptional repression of ecto-5'-nucleotidase, solute carrier family 12 member 8, and nicotinamide riboside kinase, as well as iNAD+ resetting. Our findings provide the first evidence for a sirtuin 1-mediated homeostatic response aimed at maintaining physiological iNAD+ levels in conditions of excess eNAD+ availability. These data may be of relevance for therapies designed to support the NAD+ metabolome via extracellular supplementation of the dinucleotide or its precursors.

Synergy between a shallow root system with a DRO1 homologue and localized P application improves P uptake of lowland rice.

Improved phosphorus (P) use efficiency for crop production is needed, given the depletion of phosphorus ore deposits, and increasing ecological concerns about its excessive use. Root system architecture (RSA) is important in efficiently capturing immobile P in soils, while agronomically, localized P application near the roots is a potential approach to address this issue. However, the interaction between genetic traits of RSA and localized P application has been little understood. Near-isogenic lines (NILs) and their parent of rice (qsor1-NIL, Dro1-NIL, and IR64, with shallow, deep, and intermediate root growth angles (RGA), respectively) were grown in flooded pots after placing P near the roots at transplanting (P-dipping). The experiment identified that the P-dipping created an available P hotspot at the plant base of the soil surface layer where the qsor1-NIL had the greatest root biomass and root surface area despite no genotyipic differences in total values, whereby the qsor1-NIL had significantly greater biomass and P uptake than the other genotypes in the P-dipping. The superior surface root development of qsor1-NIL could have facilitated P uptakes from the P hotspot, implying that P-use efficiency in crop production can be further increased by combining genetic traits of RSA and localized P application.

Upregulation of Vitamin C Transporter Functional Expression in 5xFAD Mouse Intestine.

The process of obtaining ascorbic acid (AA) via intestinal absorption and blood circulation is carrier-mediated utilizing the AA transporters SVCT1 and SVCT2, which are expressed in the intestine and brain (SVCT2 in abundance). AA concentration is decreased in Alzheimer's disease (AD), but information regarding the status of intestinal AA uptake in the AD is still lacking. We aimed here to understand how AA homeostasis is modulated in a transgenic mouse model (5xFAD) of AD. AA levels in serum from 5xFAD mice were markedly lower than controls. Expression of oxidative stress response genes (glutathione peroxidase 1 (GPX1) and superoxide dismutase 1 (SOD1)) were significantly increased in AD mice jejunum, and this increase was mitigated by AA supplementation. Uptake of AA in the jejunum was upregulated. This increased AA transport was caused by a marked increase in SVCT1 and SVCT2 protein, mRNA, and heterogeneous nuclear RNA (hnRNA) expression. A significant increase in the expression of HNF1α and specific protein 1 (Sp1), which drive SLC23A1 and SLC23A2 promoter activity, respectively, was observed. Expression of hSVCT interacting proteins GRHPR and CLSTN3 were also increased. SVCT2 protein and mRNA expression in the hippocampus of 5xFAD mice was not altered. Together, these investigations reveal adaptive up-regulation of intestinal AA uptake in the 5xFAD mouse model.

Transcriptomic responses to aluminum stress in tea plant leaves.

Tea plant (Camellia sinensis) is a well-known Al-accumulating plant, showing a high level of aluminum (Al) tolerance. However, the molecular mechanisms of Al tolerance and accumulation are poorly understood. We carried out transcriptome analysis of tea plant leaves in response to three different Al levels (0, 1, 4 mM, for 7 days). In total, 794, 829 and 585 differentially expressed genes (DEGs) were obtained in 4 mM Al vs. 1 mM Al, 0 Al vs. 1 mM Al, and 4 mM Al vs. 0 Al comparisons, respectively. Analysis of genes related to polysaccharide and cell wall metabolism, detoxification of reactive oxygen species (ROS), cellular transport, and signal transduction were involved in the Al stress response. Furthermore, the transcription factors such as zinc finger, myeloblastosis (MYB), and WRKY played a critical role in transcriptional regulation of genes associated with Al resistance in tea plant. In addition, the genes involved in phenolics biosynthesis and decomposition were overwhelmingly upregulated in the leaves treated with either 0 Al and 4 mM Al stress, indicating they may play an important role in Al tolerance. These results will further help us to understand mechanisms of Al stress and tolerance in tea plants regulated at the transcriptional level.

Versatile Roles of Aquaporins in Plant Growth and Development.

Aquaporins (AQPs) are universal membrane integrated water channel proteins that selectively and reversibly facilitate the movement of water, gases, metalloids, and other small neutral solutes across cellular membranes in living organisms. Compared with other organisms, plants have the largest number of AQP members with diverse characteristics, subcellular localizations and substrate permeabilities. AQPs play important roles in plant water relations, cell turgor pressure maintenance, the hydraulic regulation of roots and leaves, and in leaf transpiration, root water uptake, and plant responses to multiple biotic and abiotic stresses. They are also required for plant growth and development. In this review, we comprehensively summarize the expression and roles of diverse AQPs in the growth and development of various vegetative and reproductive organs in plants. The functions of AQPs in the intracellular translocation of hydrogen peroxide are also discussed.

Utilizing Potato Virus X to Monitor RNA Movement.

Mobility assays coupled with RNA profiling have revealed the presence of hundreds of full-length non-cell-autonomous messenger RNAs that move through the whole plant via the phloem cell system. Monitoring the movement of these RNA signals can be difficult and time consuming. Here we describe a simple, virus-based system for surveying RNA movement by replacing specific sequences within the viral RNA genome of potato virus X (PVX) that are critical for movement with other sequences that facilitate movement. PVX is a RNA virus dependent on three small proteins that facilitate cell-to-cell transport and a coat protein (CP) required for long-distance spread of PVX. Deletion of the CP blocks movement, whereas replacing the CP with phloem-mobile RNA sequences reinstates mobility. Two experimental models validating this assay system are discussed. One involves the movement of the flowering locus T RNA that regulates floral induction and the second involves movement of StBEL5, a long-distance RNA signal that regulates tuber formation in potato.

Roles of the EnvZ/OmpR Two-Component System and Porins in Iron Acquisition in Escherichia coli.

Escherichia coli secretes high-affinity Fe3+ chelators to solubilize and transport chelated Fe3+ via specific outer membrane receptors. In microaerobic and anaerobic growth environments, where the reduced Fe2+ form is predominant, ferrous transport systems fulfill the bacterial need for iron. Expression of genes coding for iron metabolism is controlled by Fur, which when bound to Fe2+ acts as a repressor. Work carried out here shows that the constitutively activated EnvZ/OmpR two-component system, which normally controls expression of the ompC and ompF porin genes, dramatically increases the intracellular pool of accessible iron, as determined by whole-cell electron paramagnetic resonance spectroscopy, by inducing the OmpC/FeoB-mediated ferrous transport pathway. Elevated levels of intracellular iron in turn activated Fur, which inhibited the ferric transport pathway but not the ferrous transport pathway. The data show that the positive effect of constitutively activated EnvZ/OmpR on feoB expression is sufficient to overcome the negative effect of activated Fur on feoB In a tonB mutant, which lacks functional ferric transport systems, deletion of ompR severely impairs growth on rich medium not supplemented with iron, while the simultaneous deletion of ompC and ompF is not viable. These data, together with the observation of derepression of the Fur regulon in an OmpC mutant, show that the porins play an important role in iron homeostasis. The work presented here also resolves a long-standing paradoxical observation of the effect of certain mutant envZ alleles on iron regulon.IMPORTANCE The work presented here solved a long-standing paradox of the negative effects of certain missense alleles of envZ, which codes for kinase of the EnvZ/OmpR two-component system, on the expression of ferric uptake genes. The data revealed that the constitutive envZ alleles activate the Feo- and OmpC-mediated ferrous uptake pathway to flood the cytoplasm with accessible ferrous iron. This activates the ferric uptake regulator, Fur, which inhibits ferric uptake system but cannot inhibit the feo operon due to the positive effect of activated EnvZ/OmpR. The data also revealed the importance of porins in iron homeostasis.

COPII Components Sar1b and Sar1c Play Distinct Yet Interchangeable Roles in Pollen Development.

The development of pollen is a prerequisite for double fertilization in angiosperms. Coat protein complex II (COPII) mediates anterograde transport of vesicles from the endoplasmic reticulum to the Golgi. Components of the COPII complex have been reported to regulate either sporophytic or gametophytic control of pollen development. The Arabidopsis (Arabidopsis thaliana) genome encodes five Sar1 isoforms, the small GTPases essential for COPII formation. By using a dominant negative approach, Sar1 isoforms were proposed to have distinct cargo specificity despite their sequence similarity. Here, we examined the functions of three Sar1 isoforms through analysis of transfer DNA insertion mutants and CRISPR/Cas9-generated mutants. We report that functional loss of Sar1b caused malfunction of tapetum, leading to male sterility. Ectopic expression of Sar1c could compensate for Sar1b loss of function in sporophytic control of pollen development, suggesting that they are interchangeable. Functional distinction between Sar1b and Sar1c may have resulted from their different gene transcription levels based on expression analyses. On the other hand, Sar1b and Sar1c redundantly mediate male gametophytic development such that the sar1b;sar1c microspores aborted at anther developmental stage 10. This study uncovers the role of Sar1 isoforms in both sporophytic and gametophytic control of pollen development. It also suggests that distinct functions of Sar1 isoforms may be caused by their distinct transcription programs.

One-carbon metabolism and folate transporter genes: Do they factor prominently in the genetic etiology of neural tube defects?

Neural tube defects (NTDs) are a broad class of congenital birth defects that result from the failure of neural tube closure during neurulation. Folic acid supplementation has been shown to prevent the occurrence of NTDs by as much as 70% in some human populations, and folate deficiency in a pregnant woman is associated with increased risk for having an NTD affected infant. Thus, folate transport-related genes and genes involved in the subsequent folate-mediated one-carbon metabolic pathway have long been considered primary candidates to study the genetic etiology of human NTDs. Herein, we review the genes involved in folate transport and one-carbon metabolism thus far identified as contributing variants that influence human NTD risk, and place these findings in the context of our evolving understanding of the complex genetic architecture underlying these defects.

Autophagy-dependent secretion: mechanism, factors secreted, and disease implications.

Although best understood as a degradative pathway, recent evidence demonstrates pronounced involvement of the macroautophagic/autophagic molecular machinery in cellular secretion. With either overexpression or inhibition of autophagy mediators, dramatic alterations in the cellular secretory profile occur. This affects secretion of a plethora of factors ranging from cytokines, to granule contents, and even viral particles. Encompassing a wide range of secreted factors, autophagy-dependent secretion is implicated in diseases ranging from cancer to neurodegeneration. With a growing body of evidence shedding light onto the molecular mediators, this review delineates the molecular machinery involved in selective targeting of the autophagosome for either degradation or secretion. In addition, we summarize the current understanding of factors and cargo secreted through this unconventional route, and describe the implications of this pathway in both health and disease. Abbreviations: BECN1, beclin 1; CAF, cancer associated fibroblast; CUPS, compartment for unconventional protein secretion; CXCL, C-X-C motif chemokine ligand; ER, endoplasmic reticulum; FGF2, fibroblast growth factor 2; HMGB1, high mobility group box 1; IDE, insulin degrading enzyme; IL, Interleukin; MAP1LC3/LC3, microtubule associated protein 1 light chain 3; MAPS, misfolding associated protein secretion; MEF, mouse embryonic fibroblast; MTORC1, MTOR complex I; PtdIns, phosphatidyl inositol; SEC22B, SEC22 homolog B, vesicle trafficking protein (gene/pseudogene); SFV, Semliki forest virus; SNCA, synuclein alpha; SQSTM1, sequestosome 1; STX, Syntaxin; TASCC, TOR-associated spatial coupling compartment; TGFB, transforming growth factor beta; TRIM16, tripartite motif containing 16; UPS, unconventional protein secretion; VWF, von Willebrand factor.

An Integrative Systems Perspective on Plant Phosphate Research.

The case for improving crop phosphorus-use-efficiency is widely recognized. Although much is known about the molecular and regulatory mechanisms, improvements have been hampered by the extreme complexity of phosphorus (P) dynamics, which involves soil chemistry; plant-soil interactions; uptake, transport, utilization and remobilization within plants; and agricultural practices. The urgency and direction of phosphate research is also dependent upon the finite sources of P, availability of stocks to farmers and reducing environmental hazards. This work introduces integrative systems approaches as a way to represent and understand this complexity, so that meaningful links can be established between genotype, environment, crop traits and yield. It aims to provide a large set of pointers to potential genes and research practice, with a view to encouraging members of the plant-phosphate research community to adopt such approaches so that, together, we can aid efforts in global food security.

NRT1.1B improves selenium concentrations in rice grains by facilitating selenomethinone translocation.

Selenium (Se) is an essential trace element for humans and other animals, yet approximately one billion people worldwide suffer from Se deficiency. Rice is a staple food for over half of the world's population that is a major dietary source of Se. In paddy soils, rice roots mainly take up selenite. Se speciation analysis indicated that most of the selenite absorbed by rice is predominantly transformed into selenomethinone (SeMet) and retained in roots. However, the mechanism by which SeMet is transported in plants remains largely unknown. In this study, SeMet uptake was found to be an energy-dependent symport process involving H+ transport, with neutral amino acids strongly inhibiting SeMet uptake. We further revealed that NRT1.1B, a member of rice peptide transporter (PTR) family which plays an important role in nitrate uptake and transport in rice, displays SeMet transport activity in yeast and Xenopus oocyte. The uptake rate of SeMet in the roots and its accumulation rate in the shoots of nrt1.1b mutant were significantly repressed. Conversely, the overexpression of NRT1.1B in rice significantly promoted SeMet translocation from roots to shoots, resulting in increased Se concentrations in shoots and rice grains. With vascular-specific expression of NRT1.1B, the grain Se concentration was 1.83-fold higher than that of wild type. These results strongly demonstrate that NRT1.1B holds great potential for the improvement of Se concentrations in grains by facilitating SeMet translocation, and the findings provide novel insight into breeding of Se-enriched rice varieties.

Genome sequencing and assessment of plant growth-promoting properties of a Serratia marcescens strain isolated from vermicompost.

BACKGROUND: Plant-bacteria associations have been extensively studied for their potential in increasing crop productivity in a sustainable manner. Serratia marcescens is a species of Enterobacteriaceae found in a wide range of environments, including soil. RESULTS: Here we describe the genome sequencing and assessment of plant growth-promoting abilities of S. marcescens UENF-22GI, a strain isolated from mature cattle manure vermicompost. In vitro, S. marcescens UENF-22GI is able to solubilize P and Zn, to produce indole compounds (likely IAA), to colonize hyphae and counter the growth of two phytopathogenic fungi. Inoculation of maize with this strain remarkably increased seedling growth and biomass under greenhouse conditions. The S. marcescens UENF-22GI genome has 5 Mb, assembled in 17 scaffolds comprising 4662 genes (4528 are protein-coding). No plasmids were identified. S. marcescens UENF-22GI is phylogenetically placed within a clade comprised almost exclusively of non-clinical strains. We identified genes and operons that are likely responsible for the interesting plant-growth promoting features that were experimentally described. The S. marcescens UENF-22GI genome harbors a horizontally-transferred genomic island involved in antibiotic production, antibiotic resistance, and anti-phage defense via a novel ADP-ribosyltransferase-like protein and possible modification of DNA by a deazapurine base, which likely contributes to its competitiveness against other bacteria. CONCLUSIONS: Collectively, our results suggest that S. marcescens UENF-22GI is a strong candidate to be used in the enrichment of substrates for plant growth promotion or as part of bioinoculants for agriculture.

Homozygous mutation in MFSD2A, encoding a lysolipid transporter for docosahexanoic acid, is associated with microcephaly and hypomyelination.

The major facilitator superfamily domain-containing protein 2A (MFSD2A) is a constituent of the blood-brain barrier and functions to transport lysophosphatidylcholines (LPCs) into the central nervous system. LPCs such as that derived from docosahexanoic acid (DHA) are indispensable to neurogenesis and maintenance of neurons, yet cannot be synthesized within the brain and are dependent on MFSD2A for brain uptake. Recent studies have implicated MFSD2A mutations in lethal and non-lethal microcephaly syndromes, with the severity correlating to the residual activity of the transporter. We describe two siblings with shared parental ancestry, in whom we identified a homozygous missense mutation (c.1205C > A; p.Pro402His) in MFSD2A. Both affected individuals had microcephaly, hypotonia, appendicular spasticity, dystonia, strabismus, and global developmental delay. Neuroimaging revealed paucity of white matter with enlarged lateral ventricles. Plasma lysophosphatidylcholine (LPC) levels were elevated, reflecting reduced brain transport. Cell-based studies of the p.Pro402His mutant protein indicated complete loss of activity of the transporter despite the non-lethal, attenuated phenotype. The aggregate data of MFSD2A-associated genotypes and phenotypes suggest that additional factors, such as nutritional supplementation or modifying genetic factors, may modulate the severity of disease and call for consideration of treatment options for affected individuals.

Elesclomol restores mitochondrial function in genetic models of copper deficiency.

Copper is an essential cofactor of cytochrome c oxidase (CcO), the terminal enzyme of the mitochondrial respiratory chain. Inherited loss-of-function mutations in several genes encoding proteins required for copper delivery to CcO result in diminished CcO activity and severe pathologic conditions in affected infants. Copper supplementation restores CcO function in patient cells with mutations in two of these genes, COA6 and SCO2, suggesting a potential therapeutic approach. However, direct copper supplementation has not been therapeutically effective in human patients, underscoring the need to identify highly efficient copper transporting pharmacological agents. By using a candidate-based approach, we identified an investigational anticancer drug, elesclomol (ES), that rescues respiratory defects of COA6-deficient yeast cells by increasing mitochondrial copper content and restoring CcO activity. ES also rescues respiratory defects in other yeast mutants of copper metabolism, suggesting a broader applicability. Low nanomolar concentrations of ES reinstate copper-containing subunits of CcO in a zebrafish model of copper deficiency and in a series of copper-deficient mammalian cells, including those derived from a patient with SCO2 mutations. These findings reveal that ES can restore intracellular copper homeostasis by mimicking the function of missing transporters and chaperones of copper, and may have potential in treating human disorders of copper metabolism.

A new perspective on lipid research in age-related macular degeneration.

There is an urgency to find new treatment strategies that could prevent or delay the onset or progression of AMD. Different classes of lipids and lipoproteins metabolism genes have been associated with AMD in a multiple ways, but despite the ever-increasing knowledge base, we still do not understand fully how circulating lipids or local lipid metabolism contribute to AMD. It is essential to clarify whether dietary lipids, systemic or local lipoprotein metabolismtrafficking of lipids in the retina should be targeted in the disease. In this article, we critically evaluate what has been reported in the literature and identify new directions needed to bring about a significant advance in our understanding of the role for lipids in AMD. This may help to develop potential new treatment strategies through targeting the lipid homeostasis.

Tea plant SWEET transporters: expression profiling, sugar transport, and the involvement of CsSWEET16 in modifying cold tolerance in Arabidopsis.

KEY MESSAGE: Thirteen SWEET transporters were identified in Camellia sinensis and the cold-suppression gene CsSWEET16 contributed to sugar compartmentation across the vacuole and function in modifying cold tolerance in Arabidopsis. The sugars will eventually be exported transporters (SWEET) family of sugar transporters in plants is a recently identified protein family of sugar uniporters that contain seven transmembrane helices harbouring two MtN3 motifs. SWEETs play important roles in various biological processes, including plant responses to environmental stimuli. In this study, 13 SWEET transporters were identified in Camellia sinensis and were divided into four clades. Transcript abundances of CsSWEET genes were detected in various tissues. CsSWEET1a/1b/2a/2b/2c/3/9b/16/17 were expressed in all of the selected tissues, whereas the expression of CsSWEET5/7/9a/15 was not detected in some tissues, including those of mature leaves. Expression analysis of nine CsSWEET genes in leaves in response to abiotic stresses, natural cold acclimation and Colletotrichum camelliae infection revealed that eight CsSWEET genes responded to abiotic stress, while CsSWEET3 responded to C. camelliae infection. Functional analysis of 13 CsSWEET activities in yeast revealed that CsSWEET1a/1b/7/17 exhibit transport activity for glucose analogues and other types of hexose molecules. Further characterization of the cold-suppression gene CsSWEET16 revealed that this gene is localized in the vacuolar membrane. CsSWEET16 contributed to sugar compartmentation across the vacuole and function in modifying cold tolerance in Arabidopsis. Together, these findings demonstrate that CsSWEET genes play important roles in the response to abiotic and biotic stresses in tea plants and provide insights into the characteristics of SWEET genes in tea plants, which could serve as the basis for further functional identification of such genes.