Functional Characterization of CsSWEET5a, a Cucumber Hexose Transporter That Mediates the Hexose Supply for Pollen Development and Rescues Male Fertility in Arabidopsis.

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 ß-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.

The mechanism of melatonin promotion on cucumber seedling growth at different nitrogen levels.

The supply level of exogenous nitrogen has a very important influence on the growth and development of cucumber. Insufficient or excessive nitrogen application will lead to metabolic disorders in the body and affect the formation of yield. Therefore, it is of great scientific and practical significance to explore the corresponding mitigation measures. Melatonin (MT) is a multi-regulatory molecule with pleiotropic effects on plant growth and development. A large number of studies have shown that the appropriate amount of melatonin supplementation is beneficial to plant growth and development by promoting root development, delaying leaf senescence, and improving fruit yield. However, the study of MT function combined with a detailed physiological analysis of nitrogen (N) absorption and metabolism in cucumber plants needs further strengthening. We performed hydroponic tests at different nitrogen levels to determine the metabolic processes associated with the enhanced tolerance to nitrogen in melatonin-treated cucumber (Cucucumis sativus L.) seedlings. Cucumber seedlings were sprayed with 100 µM melatonin or water and treated with different nitrogen in the growth chamber for 7 days. Nitrogen deficiency significantly inhibited seedling growth, and this growth inhibition was partially alleviated by melatonin. The expression analysis of related carbon and nitrogen genes showed that the genes whose expression was significantly altered by melatonin were mainly related to carbon (C) and nitrogen (N) metabolism. By enzyme activity and reactive oxygen content data analysis, melatonin-treated cucumber seedlings showed relatively stable carbon and nitrogen levels compared to untreated ones. In conclusion, MT can repair the impaired growth and development situation by regulating the nitrogen assimilation capacity and the balance between oxidation and oxidative metabolism and carbon metabolism in the cucumber under different nitrogen levels.

Cell Wall Pectin Content Refers to Favored Delivery of Negatively Charged Carbon Dots in Leaf Cells.

In this work, we systematically investigated how cell wall and cell wall components affect the delivery of charged carbon quantum dots (CDs, from -34 to +41 mV) to leaf cells of cucumber and Arabidopsis plants. Four different types of leaf cells in cucumber and Arabidopsis were used, i.e., protoplasts (without cell wall), isolated individual cells (cell wall hydrolyzed with pectinase), regenerated individual cells (cell wall regenerated from protoplast), and intact leaf cells (intact cell wall, in planta). Leaf cells were incubated with charged CDs (0.5 mg/mL) for 2 h. Confocal imaging results showed that protoplasts, regenerated individual cells, and leaf cells showed favored uptake of the negatively charged CDs (-34 mV) compared to the PEI (polyethylenimine) coated and positively charged carbon dots [PEI600-CDs (17 mV) and PEI10K-CDs (41 mV)], while in isolated individual cells, the trend is opposite. The results of the content of the cell wall components showed that no significant changes in the total cell wall content were found between isolated individual cells and regenerated individual cells (1.28 vs 1.11 mg/106 cells), while regenerated individual cells showed significant higher pectin content [water-soluble pectin (0.13 vs 0.06 mg/106 cells, P < 0.01), chelator-soluble pectin (0.04 vs 0.01 mg/106 cells, P < 0.01), and alkaline pectin (0.02 vs 0.01 mg/106 cells, P < 0.01)] and significant lower cellulose content (0.13 vs 0.32 mg/106 cells, P < 0.01) than the isolated individual cells. No difference of the hemicellulose content was found between isolated individual cells and regenerated individual cells (0.20 vs 0.21 mg/106 cells). Our results suggest that compared with cellulose and hemicellulose in the cell wall, the pectin is a more important factor referring to the favored uptake of negatively charged carbon dots in leaf cells. Overall, this work provides a method to study the role of cell wall components in the uptake of nanoparticles in plant cells and also points out the importance of understanding the interactions between cell barriers and nanoparticles to design nanoparticles for agricultural use.

Cucumis sativus (Cucurbitaceae) seed oil prevents benzo(a)pyrene-induced prostate cancer in vitro and in vivo.

Despite enormous progress in modern medicine, prostate cancer (PCa) remains a major public health problem due to its high incidence and mortality. Although studies have shown in vitro antitumor effects of cucurbitacins from Cucumis sativus, the in vivo anticancer effect of the seed oil as a whole, has yet to be demonstrated. The present study evaluated the in vitro anticancer mechanisms of C. sativus (CS) seed oil and its possible chemopreventive potential on benzo(a)pyrene (BaP)-induced PCa in Wistar rat. In vitro cell growth, clone formation, cell death mechanism, cell adhesion and migration as well as expression of integrins ß-1 and ß-4 were assessed. In vivo PCa was induced in 56 male rats versus 8 normal control rats, randomized in normal (NOR) and negative (BaP) control groups which, received distilled water; the positive control group (Caso) was treated with casodex (13.5 mg/kg BW). One group received the total seed extract at the dose of 500 mg/kg BW; while the remaining three groups were treated with CS seed oil at 42.5, 85, and 170 mg/kg BW. The endpoints were: morphologically (prostate tumor weight and volume), biochemically (total protein, prostate specific antigen (PSA), oxidative stress markers such as MDA, GSH, catalase, and SOD) and histologically. As results, CS seed oil significantly and concentration-dependently reduced the DU145 prostate cancer cell growth and clone formation (optimum = 100 µg/mL). It slightly increased the number of apoptotic cells and inhibited the migration and invasion of DU145 cells, while it decreased their adhesion to immobilized collagen and fibrinogen. The expression of integrin ß-1 and ß-4 was increased in presence of 100 µg/mL CS oil. In vivo, the BaP significantly elevated the incidence of PC tumors (75%), the total protein and PSA levels, pro-inflammatory cytokines (TNF-α, IL-1, and IL-6) and MDA levels compared to NOR. CS seeds oil significantly counteracted the effect of BaP by decreasing significantly the PC incidence (12.5%), and increasing the level of antioxidant (SOD, GSH, and catalase) and anti-inflammatory cytokine IL-10 in serum. While in BaP group PCa adenocarninoma was the most representative neoplasm, rats treated with 85 and 170 mg/kg prevented it in the light of the casodex. It is conclude that CS may provide tumor suppressive effects in vitro and in vivo which makes it an interesting candidate to support the current treatment protocol.

Titanium dioxide nanoparticles require K+ and hydrogen sulfide to regulate nitrogen and carbohydrate metabolism during adaptive response to drought and nickel stress in cucumber.

Crop plants face severe yield losses worldwide owing to their exposure to multiple abiotic stresses. The study described here, was conducted to comprehend the response of cucumber seedlings to drought (induced by 15% w/v polyethylene glycol 8000; PEG) and nickel (Ni) stress in presence or absence of titanium dioxide nanoparticle (nTiO2). In addition, it was also investigated how nitrogen (N) and carbohydrate metabolism, as well as the defense system, are affected by endogenous potassium (K+) and hydrogen sulfide (H2S). Cucumber seedlings were subjected to Ni stress and drought, which led to oxidative stress and triggered the defense system. Under the stress, N and carbohydrate metabolism were differentially affected. Supplementation of the stressed seedlings with nTiO2 (15 mg L-1) enhanced the activity of antioxidant enzymes, ascorbate-glutathione (AsA-GSH) system and elevated N and carbohydrates metabolism. Application of nTiO2 also enhanced the accumulation of phytochelatins and activity of the enzymes of glyoxalase system that provided additional protection against the metal and toxic methylglyoxal. Osmotic stress brought on by PEG and Ni, was countered by the increase of proline and carbohydrates levels, which helped the seedlings keep their optimal level of hydration. Application nTiO2 improved the biosynthesis of H2S and K+ retention through regulating Cys biosynthesis and H+-ATPase activity, respectively. Observed outcomes lead to the conclusion that nTiO2 maintains redox homeostasis, and normal functioning of N and carbohydrates metabolism that resulted in the protection of cucumber seedlings against drought and Ni stress. Use of 20 mM tetraethylammonium chloride (K+- channel blocker), 500 µM sodium orthovanadate (PM H+-ATPase inhibitor), and 1 mM hypotaurine (H2S scavenger) demonstrate that endogenous K+ and H2S were crucial for the nTiO2-induced modulation of plants' adaptive responses to the imposed stress.

Expression of B. subtilis Phytase gene driven by fruit specific E8 promoter for enhanced minerals, metabolites and phytonutrient in cucumber fruit.

The fruit nutrigenomics is an interesting and important research area towards nutrition enhancement. The phytic acid is one of the major antinutrient compound, present in seeded fruits and crops. It hinders the absorption of iron (Fe), zinc (Zn), magnesium (Mg), potassium (K) and calcium (Ca), causing mineral deficiencies. In the present study, the BsPhy gene was overexpressed in the cucumber fruits using the tomato fruit specific E8 and constitutive CaMV 35S promoter. The E8 promoter imparted heterologous expression of GUS gene in cucumber fruits, furthermore, the fruit specific expression of E8 promoter with BsPhy gene was confirmed in transgenics (E8::BsPhy) using anti rabbit-phytase antibody. The physio-biochemical analysis of transgenics revealed, maximum phytase activity in E8::BsPhy cucumber fruits at 10 days after anthesis (DAA) compared to 35S::BsPhy and wild-type (WT) fruits. Consequently, E8::BsPhy fruits also showed increased amount of inorganic phosphorus (Pi), total phosphorus (P), minerals (Zn, Fe, Mg, K, Ca), total carotenoid and other macronutrients at 10 DAA compared to 35S::BsPhy fruits. The metabolite profiling of fruits (10 DAA) showed increased sugars, amino acids, sugar acids and polyols, in both E8::BsPhy and 35S::BsPhy transgenics suggesting higher phytate metabolism, compared to WT fruits. Interestingly, both the transgenic fruits showed higher fruit biomass and yield along with improved nutritional quality, which can be attributed to increased P and Zn contents in transgenic fruits, compared to WT fruits. Our findings reveal that the BsPhy gene enhances minerals and macronutrients in transgenic cucumber fruits making it nutritious and healthy.

The Effect of Combining Post-Harvest Calcium Nanoparticles with a Salicylic Acid Treatment on Cucumber Tissue Breakdown via Enzyme Activity during Shelf Life.

In the present study, an experiment was carried out on the postharvest of cucumber fruit during a 14-day shelf life. The aim was to assess the impact of calcium nanoparticles (CaNPs) blended with different concentrations of salicylic acid (SA) on the shelf life of cucumbers during the seasons of 2018 and 2019. The investigation further monitored the influences of CaNPs-SA on some physical properties of cucumber, including the percentage weight loss, color, and fruit firmness. In addition, chemical properties, such as total soluble solids (SSC%), total acidity (TA%), total soluble sugars, and chlorophyll pigmentation of the fruit skin, were assessed during a 14-day shelf lifeCell wall degradation enzymes (CWEAs) such as polygalacturonase (PG), cel-lulase (CEL), xylanase (XYL), and pectinase (PT) were also researched. In addition, the generation rates of H2O2 and O2•- were calculated, as well as the reduction of DPPH. The lipid peroxidation (malondialdehyde, MDA) and cell membrane permeability (IL%) of cell wall composites were also determined. CaNPs-SA at 2 mM suppressed CWEAs, preserved fruit quality, reduced weight loss throughout the shelf-life period, and reduced the percent leakage value. At this concentration, we also found the lowest levels of MDA and the highest levels of DPPH.

Garlic Volatile Diallyl Disulfide Induced Cucumber Resistance to Downy Mildew.

Allicin compositions in garlic are used widely as fungicides in modern agriculture, in which diallyl disulfide (DADS) is a major compound. Downy mildew, caused by Pseudoperonospora cubensis (P. cubensis), is one of the most destructive diseases and causes severe yield losses in cucumbers. To explore the potential mechanism of DADS-induced cucumber resistance to downy mildew, cucumber seedlings were treated with DADS and then inoculated with P. cubensis at a 10-day interval. Symptom observation showed that DADS significantly induced cucumber resistance to downy mildew. Furthermore, both lignin and H2O2 were significantly increased by DADS treatment to responding P. cubensis infection. Simultaneously, the enzyme activities of peroxidase (POD) in DADS-treated seedlings were significantly promoted. Meanwhile, both the auxin (IAA) and salicylic acid (SA) contents were increased, and their related differentially expressed genes (DEGs) were up-regulated when treated with DADS. Transcriptome profiling showed that many DEGs were involved in the biological processes of defense responses, in which DEGs on the pathways of 'phenylpropanoid biosynthesis', 'phenylalanine metabolism', 'MAPK signaling', and 'plant hormone signal transduction' were significantly up-regulated in DADS-treated cucumbers uninoculated with the pathogen. Based on the results of several physiological indices and transcriptomes, a potential molecular mechanism of DADS-induced cucumber resistance to downy mildew was proposed and discussed. The results of this study might give new insight into the exploration of the induced resistance mechanism of cucumber to downy mildew and provide useful information for the subsequent mining of resistance genes in cucumber.

Genetic and Transcriptomic Analysis Reveal the Molecular Basis of Photoperiod-Regulated Flowering in Xishuangbanna Cucumber (Cucumis sativus L. var. xishuangbannesis Qi et Yuan).

Xishuangbanna (XIS) cucumber (Cucumis sativus L. var. xishuangbannesis Qi et Yuan), is a botanical variety of cucumber cultivars native to southwest China that possesses excellent agronomic traits for cucumber improvement. However, breeding utilization of XIS cucumber is limited due to the current poor understanding of its photoperiod-sensitive flowering characteristics. In this study, genetic and transcriptomic analysis were conducted to reveal the molecular basis of photoperiod-regulated flowering in XIS cucumber. A major-effect QTL locus DFF1.1 was identified that controls the days to first flowering (DFF) of XIS cucumbers with a span of 1.38 Mb. Whole-genome re-sequencing data of 9 cucumber varieties with different flowering characteristics in response to photoperiod suggested that CsaNFYA1 was the candidate gene of DFF1.1, which harbored a single non-synonymous mutation in its fifth exon. Transcriptomic analysis revealed the positive roles of auxin and ethylene in accelerating flowering under short-day (SD) light-dark cycles when compared with equal-day/night treatment. Carbohydrate storage and high expression levels of related genes were important reasons explaining early flowering of XIS cucumber under SD conditions. By combining with the RNA-Seq data, the co-expression network suggested that CsaNFYA1 integrated multiple types of genes to regulate the flowering of XIS cucumber. Our findings explain the internal regulatory mechanisms of a photoperiodic flowering pathway. These findings may guide the use of photoperiod shifts to promote flowering of photoperiod-sensitive crops.

Dietary Supplementation with Exogenous Sea-Cucumber-Derived Ceramides and Glucosylceramides Alleviates Insulin Resistance in High-Fructose-Diet-Fed Rats by Upregulating the IRS/PI3K/Akt Signaling Pathway.

Endogenous ceramide is considered to be associated with the progress of insulin resistance. However, the effects of dietary exogenous glucosylceramides and ceramides on insulin resistance are unclear. A model of fructose-induced male Sprague Dawley rats was used to compare the effects of sea-cucumber-derived glucosylceramides and ceramides on insulin resistance. Both glucosylceramides and ceramides significantly improved glucose tolerance, reduced the concentrations of serum glucose and glycosylated hemoglobin, and alleviated the accompanied hypertension. Ceramides significantly enhanced glycogen levels in skeletal muscle, whereas glucosylceramides significantly increased the hepatic glycogen levels. Moreover, glucosylceramides alleviated insulin resistance by inhibiting gluconeogenesis, promoting glycogen synthesis and insulin signal transduction in the liver; meanwhile, ceramides were mainly due to the promotion of glycogen synthesis and insulin signal transduction in skeletal muscle. Additionally, glucosylceramides and ceramides effectively attenuated inflammation in adipose tissue. These results indicate that glucosylceramides and ceramides have potential value in the prevention and alleviation of insulin resistance.

Copper toxicity affects phosphorus uptake mechanisms at molecular and physiological levels in Cucumis sativus plants.

Due to the deliberate use of cupric fungicides in the last century for crop-defence programs, copper (Cu) has considerably accumulated in the soil. The concentrations of Cu often exceed the safety limits of risk assessment for Cu in soil and this may cause toxicity in plants. Copper toxicity induces nutritional imbalances in plants and constraints to plants growth. These aspects might be of paramount importance in the case of phosphorus (P), which is an essential plant macronutrient. In this work, hydroponically grown cucumber plants were used to investigate the influence of the exposure to different Cu concentrations (0.2, 5, 25 and 50 µM) on i) the phenotypic traits of plants, particularly at root level, ii) the nutrient content in both roots and shoots, and iii) the P uptake mechanisms, considering both the biochemical and molecular aspects. At high Cu concentrations (i.e. above 25 µM), the shoot and root growth resulted stunted and the P influx rate diminished. Furthermore, two P transporter genes (i.e. CsPT1.4 and CsPT1.9) were upregulated at the highest Cu concentration, albeit with different induction kinetics. Overall, these results confirm that high Cu concentrations can limit the root acquisition of P, most likely via a direct action on the uptake mechanisms (e.g. transporters). However, the alteration of root plasma membrane permeability induced by Cu toxicity might also play a pivotal role in the observed phenomenon.

Effect of Cucumis sativus on Dysfunctional 3T3-L1 Adipocytes.

Obesity is caused by lipid accumulation in adipose tissues inducing adipocyte dysfunction, characterized by insulin resistance, increased lipolysis, oxidative stress, and inflammation, leading to increased levels of adipokines. Herein the capacity of the subfractions (SFs) SF1, SF2, and SF3 from the Cucumis sativus aqueous fraction and their combinations (M) to control adipocyte dysfunction in vitro, in 3T3-L1 adipocytes was studied. Adipocytes, previously treated with dexamethasone or IL-1 to induce dysfunction, were incubated with different concentrations of the subfractions for 24 h. 2-deoxyglucose consumption and glycerol release were evaluated, and a surface model was constructed to determine the most effective SF concentrations to improve both parameters. Effective SF combinations were assessed in their capacity to control metabolic, pro-oxidative, and pro-inflammatory conditions. SF1, SF2 (40 µg/ml each) and SF3 (20 µg/ml) improved 2-deoxyglucose consumption by 87%, 57%, and 87%, respectively. SF1 and SF2 (5 µg/ml each) and SF3 (40 µg/mL) increased glycerol secretion by 10.6%, 18.9%, and 11.8%, respectively. Among five combinations tested, only M4 (SF1 40 µg/ml:SF2 60 µg/ml:SF3 30 µg/ml) and M5 (SF1 40 µg/ml:SF2 60 µg/mL:SF3 10 µg/ml) controlled effectively the metabolic, pro-oxidative, and proinflammatory conditions studied. Glycine, asparagine, and arginine were the main components in these SFs.

Identification and Allelopathy of Green Garlic (Allium sativum L.) Volatiles on Scavenging of Cucumber (Cucumis sativus L.) Reactive Oxygen Species.

Garlic and formulations containing allicin are used widely as fungicides in modern agriculture. However, limited reports are available on the allelopathic mechanism of green garlic volatile organic compounds (VOCs) and its component allelochemicals. The aim of this study was to investigate VOCs of green garlic and their effect on scavenging of reactive oxygen species (ROS) in cucumber. In this study, green garlic VOCs were collected by HS-SPME, then analyzed by GS-MS. Their biological activity were verified by bioassays. The results showed that diallyl disulfide (DADS) is the main allelochemical of green garlic VOCs and the DADS content released from green garlic is approximately 0.08 mg/g. On this basis, the allelopathic effects of green garlic VOCs in vivo and 1 mmol/L DADS on scavenging of ROS in cucumber seedlings were further studied. Green garlic VOCs and DADS both reduce superoxide anion and increase the accumulation of hydrogen peroxide of cucumber seedlings. They can also regulate active antioxidant enzymes (SOD, CAT, POD), antioxidant substances (MDA, GSH and ASA) and genes (CscAPX, CsGPX, CsMDAR, CsSOD, CsCAT, CsPOD) responding to oxidative stress in cucumber seedlings.

FePO4 nanoparticles produced by an industrially scalable continuous-flow method are an available form of P and Fe for cucumber and maize plants.

Nanomaterials are widely used in medical and pharmaceutical fields, but their application in plant nutrition is at its infancy. Phosphorous (P) and iron (Fe) are essential mineral nutrients limiting in a wide range of conditions the yield of crops. Phosphate and Fe fertilizers to-date on the market display low efficiency (P fertilizers) and low persistence in soil (Fe fertilizers) and negatively affect the environment. In the tentative to overcome these problems, we developed a continuous industrially scalable method to produce FePO4 NPs based on the rapid mixing of salt solutions in a mixing chamber. The process, that included the addition of citrate as capping agent allowed to obtain a stable suspension of NPs over the time. The NPs were tested for their effectiveness as P and Fe sources on two hydroponically grown crop species (cucumber and maize) comparing their effects to those exerted by non-nanometric FePO4 (bulk FePO4). The results showed that FePO4 NPs improved the availability of P and Fe, if compared to the non-nano counterpart, as demonstrated by leaf SPAD indexes, fresh biomasses and P and Fe contents in tissues. The results open a new avenue in the application of nanosized material in the field of plant nutrition and fertilization.

The garlic allelochemical DADS influences cucumber root growth involved in regulating hormone levels and modulating cell cycling.

Most allelochemicals are phytotoxic to the receiver plants and may influence the cell micro- and ultrastructure, cell division, phytohormone levels, and ultimately growth. In order to understand the allelopathic potential of garlic, the effects of its main bioactive allelochemical diallyl disulfide (DADS), experiments were carried out to observe the seed germination, root growth, and developmental responses in cucumber seedlings treated with various concentrations of DADS. The obtained data suggested active influence of DADS on cucumber root growth and development. Significant responses were observed in early root growth and elongation, mitotic cell division and elongation, and root architecture modulation. The effect, however, was dose dependent, and lower concentrations of DADS proved to be promotional whereas higher concentrations of DADS inhibited cucumber root growth and development. Relative root elongation (RRE) revealed that DADS could increase growth of cucumber roots in the early developmental days. Moreover, DADS application significantly influenced mitosis-related gene expression. Observed genes CYCA and CDKB were initially downregulated in the first 24 h but significantly upregulated after 48 h, while gene CDKA was upregulated in the first 24 h. Similarly, DADS application significantly altered primary plant hormones, such as IAA, ABA, GA3, and ZR, in the cucumber roots. Taken together, low concentrations of DADS treatment could promote cucumber root growth and induce main root elongation by upregulating CDKA and CDKB gene expression and regulating hormone balance in root. The current findings offer insight into the allelopathic potential of garlic allelochemical DADS and can be considered vital for establishing plant allelopathic studies.

Dissipation behaviour and dietary risk assessment of boscalid, triflumizole and its metabolite (FM-6-1) in open-field cucumber based on QuEChERS using HPLC-MS/MS technique.

BACKGROUND: To resist plant diseases, boscalid and triflumizole have been applied to cucumbers frequently. However, the residue and dietary risk assessment of these fungicides in cucumber should be given attention for food safety. RESULTS: An effective and highly sensitive method based on the liquid chromatography-tandem mass spectrometry technique for simultaneous multidetermination of boscalid, triflumizole and its metabolite (FM-6-1) in a cucumber ecosystem was established and validated. Field experiments were conducted in three different locations, where boscalid and triflumizole (35% suspension concentration) were applied at 253 g of active ingredient (a.i.) per hectare (the recommended high dosage) and 379.5 g a.i. ha-1 (1.5 times the recommended high dosage) in each location. The limits of quantification and the limits of detection of the proposed method ranged from 0.01 to 0.05 mg kg-1 and 3.9 × 10-5 to 7.5 × 10-4 mg L-1 respectively. The mean recoveries and relative standard deviations of these compounds were 80-105% and 1.0-6.1% respectively. The dissipation dynamics of compounds followed pseudo-first-order kinetic models remarkably, with a half-value period of 2.3-40.8 days. The residues of boscalid and triflumizole in cucumber at harvest were below 0.66 mg kg-1 and 0.07 mg kg-1 respectively. The results of the dietary risk assessments have shown a low dietary risk of compounds in cucumber with hazard ratios <1 and hazard index <1. CONCLUSION: These results from the experiments are the most important for putting a guide on reasonable usage of these fungicides under the open-field conditions in China. © 2018 Society of Chemical Industry.

Elevated and super-elevated CO2 differ in their interactive effects with nitrogen availability on fruit yield and quality of cucumber.

BACKGROUND: Elevated carbon dioxide (CO2 ) and nitrogen (N) availability can interactively promote cucumber yield, but how the yield increase is realized remains unclear, whilst the interactive effects on fruit quality are unknown. In this study, cucumber plants (Cucumis sativus L. cv. Jinmei No. 3) were grown in a paddy soil under three CO2 concentrations - 400 (ambient CO2 ), 800 (elevated CO2 , eCO2 ) and 1200 µmol mol-1 (super-elevated CO2 ) - and two N applications - 0.06 (low N) and 0.24 g N kg-1 soil (high N). RESULTS: Compared with ambient CO2 , eCO2 increased yield by 106% in high N but the increase in total biomass was only 33%. This can result from greater carbon translocation to fruits from other organs, indicated by the increased biomass allocation from stems and leaves, particularly source leaves, to fruits and the decreased concentrations of fructose and glucose in source leaves. Super-elevated CO2 reduced the carbon allocation to fruits thus yield increase (71%). Additionally, eCO2 also increased the concentrations of fructose and glucose in fruits, maintained the concentrations of dietary fiber, phosphorus, potassium, calcium, magnesium, sulfur, manganese, copper, molybdenum and sodium, whilst it decreased the concentrations of nitrate, protein, iron, and zinc in high N. Compared with eCO2 , super-elevated CO2 can still improve the fruit quality to some extent in low N availability. CONCLUSIONS: Elevated CO2 promotes cucumber yield largely by carbon allocation from source leaves to fruits in high N availability. Besides a dilution effect, carbon allocation to fruits, carbohydrate transformation, and nutrient uptake and assimilation can affect the fruit quality. © 2018 Society of Chemical Industry.

Preparation of cucumber seed peptide-calcium chelate by liquid state fermentation and its characterization.

A specific cucumber seed peptide (CSP) was successfully produced by liquid state fermentation with B. subtilis HYT. Then the CSP was divided into four kind molecular weight components (CSP, untreated; CSP1, MW>10kDa; CSP2, 6kDa

Changes in the DNA methylation pattern of the host male gametophyte of viroid-infected cucumber plants.

Eukaryotic organisms exposed to adverse conditions are required to show a certain degree of transcriptional plasticity in order to cope successfully with stress. Epigenetic regulation of the genome is a key regulatory mechanism allowing dynamic changes of the transcriptional status of the plant in response to stress. The Hop stunt viroid (HSVd) induces the demethylation of ribosomal RNA (rRNA) in cucumber (Cucumis sativus) leaves, leading to increasing transcription rates of rRNA. In addition to the clear alterations observed in vegetative tissues, HSVd infection is also associated with drastic changes in gametophyte development. To examine the basis of viroid-induced alterations in reproductive tissues, we analysed the cellular and molecular consequences of HSVd infection in the male gametophyte of cucumber plants. Our results indicate that in the pollen grain, accumulation of HSVd RNA induces a decondensation of the generative nucleus that correlates with a dynamic demethylation of repetitive regions in the cucumber genome that include rRNA genes and transposable elements (TEs). We therefore propose that HSVd infection impairs the epigenetic control of rRNA genes and TEs in gametic cells of cucumber, a phenomenon thus far unknown to occur in this reproductive tissue as a consequence of pathogen infection.

Physiological and proteomic analysis of selenium-mediated tolerance to Cd stress in cucumber (Cucumis sativus L.).

Selenium can mitigate cadmium toxicity in plants. However, the mechanism of this alleviation has not been fully understood. In the present study, the role of Se in inducing tolerance to Cd stress in cucumber was elucidated. Results showed that Se significantly alleviated Cd-induced growth inhibition, reduced Cd concentration, increased SPAD value and improved photosynthetic performance. Through proteomic analysis by two-dimensional gel electrophoresis (2-DE) coupled with mass spectrometry, 26 protein spots were identified, which were significantly influenced by Cd stress and/or Se application. Among these proteins, the abundance of 21 spots (10 in leaves and 11 in roots) were repressed in Cd-treated and up-accumulated or no-changed in Cd+Se-treated cucumber. These altered proteins were involved in the response to stress, metabolism, photosynthesis and storage, they were including glutathione S-transferase F8, heat shock protein STI-like, peroxidase, ascorbate oxidase, fructose-bisphosphate aldolase 2, NiR, Rieske type ion sulfur subunit and PsbP domain-containing protein 6. Furthermore, we identified five proteins with an increase in relative abundance after Cd treatment, they were involved in the functional groups active in response to stress and transport. The present study provided novel insights into Se-mediated tolerance of cucumber seedlings against Cd toxicity at the proteome level.