Relative Membrane Permeability Research Articles

Differential Effects of Plant Growth-Promoting Rhizobacteria on Maize Growth and Cadmium Uptake

Maize is a plant known for food, feed, and energy value, but being a greater biomass, it may also be utilized to extract pollutants from soil. Plant growth-promoting rhizobacteria (PGPR) may act as biofertilizer to improve plant health and indirectly may enhance metal extraction. This study focuses on five bacterial strains isolated from the vegetable (Bitter gourd) rhizosphere irrigated with industrial effluent and characterized for various plant growth-promoting activities. Based on 16S rRNA gene sequencing, bacterial strains belonging to the genera, Bacillus (CIK-517, CIK-519), Klebsiella (CIK-518), Leifsonia (CIK-521), and Enterobacter (CIK-521R), were tested for their ability to promote maize growth in axenic conditions. Results showed negative and positive regulation of maize growth by the exogenous application of Cd and PGPR, respectively. Seed germination assays revealed significant reduction in relative seedling growth of maize cultivars upon Cd exposure (0–80 mg Cd L−1). The tested strains showed tolerance to Cd (1.78–4.45 mmol L−1) and were positive for catalase, oxidase, phosphate solubilization, exopolysaccharide (EPS), and auxin production, whereas CIK-518, CIK-519, and CIK-521R were negative for EPS, phosphate solubilization, and oxidase activities, respectively. Bacterial strains significantly increased shoot/root growth and their dry biomass in normal and Cd-contaminated soil as compared to their respective controls. None of the strains showed significant effects on relative water content or membrane permeability; however, Cd uptake significantly increased in plant tissues upon bacterial inoculation. Bacterial strains CIK-518 and CIK-521R are effective colonizers and thus can be potential inoculants to promote maize growth and Cd extraction/stabilization in Cd-contaminated soil.

Expression of OsCAS (Calcium-Sensing Receptor) in an Arabidopsis Mutant Increases Drought Tolerance.

The calcium-sensing receptor (CaS), which is localized in the chloroplasts, is a crucial regulator of extracellular calcium-induced stomatal closure in Arabidopsis. It has homologs in Oryza sativa and other plants. These sequences all have a rhodanese-like protein domain, which has been demonstrated to be associated with specific stress conditions. In this study, we cloned the Oryza sativa calcium-sensing receptor gene (OsCAS) and demonstrated that OsCAS could sense an increase of extracellular Ca2+ concentration and mediate an increase in cytosolic Ca2+ concentration. The OsCAS gene was transformed into an Arabidopsis CaS knockout mutant (Salk) and overexpressed in the transgenic plants. OsCAS promoted stomatal closure. We screened homozygous transgenic Arabidopsis plants and determined physiological indices such as the oxidative damage biomarker malondialdehyde (MDA), relative membrane permeability (RMP), proline content, and chlorophyll fluorescence parameters, after 21 days of drought treatment. Our results revealed lower RMP and MDA contents and a higher Proline content in transgenic Arabidopsis plants after drought stress, whereas the opposite was observed in Salk plants. With respect to chlorophyll fluorescence, the electron transport rate and effective PSII quantum yield decreased in all lines under drought stress; however, in the transgenic plants these two parameters changed fewer and were higher than those in wild-type and Salk plants. The quantum yield of regulated energy dissipation and nonregulated energy dissipation in PSII were higher in Salk plants, whereas these values were lower in the transgenic plants than in the wild type under drought stress. The above results suggest that the transgenic plants showed better resistance to drought stress by decreasing damage to the cell membrane, increasing the amount of osmoprotectants, and maintaining a relatively high photosynthetic capacity. In conclusion, OsCAS is an extracellular calcium-sensing receptor that helps to compensate for the absence of CaS in Arabidopsis and increases the drought stress tolerance of transgenic plants.

Exogenous application of trehalose alters growth, physiology and nutrient composition in radish (Raphanus sativus L.) plants under water-deficit conditions

Radish (Raphanus sativus L.) is one of the most desirable vegetables grown in many parts of the world due to its short growth period and high nutritious value. To explore its cultivation in rain-fed areas, the present study was conducted to assess the role of foliar-applied trehalose (25 and 50 mM) in two radish cultivars, Manu and 40-days, grown under non-stress (100 % FC) and water stress (60 % FC) conditions. Under drought stress conditions, shoot fresh and dry weights, shoot and root lengths, photosynthetic rate (A), transpiration rate (E), stomatal conductance (gs), internal CO2 concentration (Ci), relative water contents (RWC), shoot K+ and P and shoot and root Ca2+ decreased, while water-use efficiency (WUE) and relative membrane permeability (RMP) increased in both radish cultivars. External fortification with trehalose improved shoot fresh and dry weights, chlorophyll a content and accumulation of P in shoot, but decreased RMP in both cultivars. However, trehalose application caused no significant alteration in shoot and root lengths, A, chl. b content, Ci, WUE and RWC. Of both radish cultivars, cv. 40-days excelled cv. Manu in shoot fresh weight, shoot length, E, gs, Ci, WUE and shoot K+ and Ca2+, whereas the reverse was true for A and RMP. Overall, water stress adversely affected growth and other physiological attributes appraised, but foliar-applied trehalose improved only growth and shoot P and decreased RMP. The relatively better growth of cv. 40-days could be due to trehalose-induced physio-biochemical attributes other than those measured in the present study except trehalose-induced improvement in shoot P and reduction in RMP. Therefore, a further study needs to be carried out to find out the role of trehalose on attributes which are directly or indirectly involved in plant growth under stress conditions.

Effects of 1-methylcyclopropene on superficial scald and related metabolism in ‘Wujiuxiang’ pears during cold storage

‘Wujiuxiang’ ( Pyrus bretschneideri R. × Pyrus communis L.) pears often suffer from superficial scald after long-term cold storage. In this study, harvested ‘Wujiuxiang’ pear fruits were fumigated with 1-MCP at concentrations of 0.5 μL/L and 1.0 μL/L and subsequently stored at low temperature (0 °C). The superficial scald index; flesh firmness; total soluble solids (TSS) content; respiration and ethylene production rates; relative membrane permeability; concentrations of α -farnesene, conjugated trienols (CTols), and hydrogen peroxide (H 2 O 2 ); and activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and lipoxygenase (LOX) of the peel were investigated. The results showed that compared with control, 1-MCP reduced the index of superficial scald; maintained a higher firmness and a lower TSS content; inhibited the accumulation of H 2 O 2 , α -farnesene and conjugated trienols and the increase in cell membrane permeability; and maintained a higher activity of APX, SOD and CAT and a lower activity of LOX. These findings indicate that 1-MCP regulates the activities of H 2 O 2 -scavenging enzymes to inhibit the accumulation of H 2 O 2 and thereby reduces cell membrane damage and inhibits the accumulation of conjugated trienols. Thus, 1-MCP could decrease the incidence of superficial scald in ‘Wujiuxiang’ pears.

English

A pot experiment treated with cadmium (Cd) was conducted to evaluate the physiological and yield responses of peanut to cadmium in different growth stages. The results indicated that the peanut treated with cadmium level of 12 mg/kg did not cause obvious visible toxic symptoms, while the antioxidant enzymes activities concluding superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) showed significant decrease in tested growth stages. The content of total chlorophyll decreased significantly in the growth stages (P < 0.05). The results indicated that Cd destroyed the balance of free radical metabolisms, which resulted in increasing malondialdehyde (MDA) content and the relative cell membrane permeability (RMP). The kernel yield and kernel rate per pot showed significant decrease under cadmium stress (P < 0.05). The varieties FengHua3, HuaYu20 and Luhua 12 showed more sensitive than the other varieties. The results indicated that the MDA, total chlorophyll content and RMP may be more sensitive or indicative than the others under Cadmium stress.   Key words: Peanut (Arachis hypogaea L.), cadmium, phytotoxicity, physiological mechanism. &nbsp

Responses to the Irrigation Water Amount of Spinach Supplemented with Organic Amendment in Greenhouse Conditions

The effect of organic amendment applications on some agrophysiological properties of pot-grown spinach was investigated under drought stress. The I1, I2, I3, and I4 irrigation treatments received water amounts up to 100, 80, 60, and 40 percent of evaporation from a reduced pan, respectively. A liquid organic amendment was applied to spinach seeds as seed treatment at the ratios of 0.1 percent (H1) and 0.2 percent (H3). Furthermore, in the H2 and H4 treatments the amendment was foliar applied to spinach seedlings at the ratios of 0.1 percent and 0.2 percent in addition to the seed treatments, respectively. Organic amendment treatments positively affected root and leaf growth. The plants responded to water stress by lower growth. Leaf relative water content, membrane permeability, chlorophyll reading, and stomatal conductance values also indicated significant changes. These results support the view that organic amendment application increased growth. However, it could not provide a significant contribution for growth under water stress.

Physiological responses of Kosteletzkya virginica to coastal wetland soil.

Effects of salinity on growth and physiological indices of Kosteletzkya virginica seedlings were studied. Plant height, fresh weight (FW), dry weight (DW), and net photosynthetic rate (P n) increased at 100 mM NaCl and slightly declined at 200 mM, but higher salinity induced a significant reduction. Chlorophyll content, stomatal conductance (G s), intercellular CO2 concentration (C i), and transpiration rate (E) were not affected under moderate salinities, while markedly decreased at severe salinities except for the increased C i at 400 mM NaCl. Furthermore, no significant differences of F v/F m and ΦPSII were found at lower than 200 mM NaCl, whereas higher salinity caused the declines of F v/F m, ΦPSII, and qP similar to P n, accompanied with higher NPQ. Besides, salt stress reduced the leaf RWC, but caused the accumulation of proline to alleviate osmotic pressure. The increased activities of antioxidant enzymes maintained the normal levels of MDA and relative membrane permeability. To sum up, Kosteletzkya virginica seedlings have good salt tolerance and this may be partly attributed to its osmotic regulation and antioxidant capacity which help to maintain water balance and normal ROS level to ensure the efficient photosynthesis. These results provided important implications for Kosteletzkya virginica acting as a promising multiuse species for reclaiming coastal soil.

Enhanced Membrane Permeability in E. coli Induced by Extracellular Adenosine Triphosphate

It is well known that the addition of adenosine triphosphate (ATP) to the extracellular suspension of a variety of cell types increases the relative permeability of the cell membrane to a number of molecular species. We have previously demonstrated the use of time-resolved second-harmonic laser scattering (SHLS) and bright-field transmission microscopy (TM) as complementary real-time probes of molecular uptake in living cells (1,2) which are capable of revealing membrane-specific transport kinetics. Herein, we employ SHLS and TM to quantify the ATP-induced enhancement of membrane permeability in living Gram-negative bacteria. Specifically, we characterize the variation of the uptake rate of the cationic triphenyl methane dye malachite green (MG) into E. coli as a function of the concentration of ATP added to the extracellular suspension. As expected, due to the presence of the outer membrane (OM) porin channels, no change in the OM transport kinetics is observed. Conversely, transport across the cytoplasmic membrane (CM) is shown to increase by nearly an order of magnitude. Additionally, the presence of ATP results in an increase of MG adsorption onto the CM, suggesting that the permeability enhancement likely arises from a potential differential across the membrane. To gain mechanistic insight into the observed enhancement, we conduct control experiments using liposomes generated from lipids isolated from E. coli, including liposomes 1) composed solely of lipids, 2) with internalized ATP, 3) reconstituted with nucleoside transporters, and/or 4) reconstituted with ATP binding cassette cation transporters (and associated internalized cations). Subsequently, using model systems of gradually increasing complexity, the effectiveness of each membrane component on the observed permeability enhancement is compared.1. Zeng, J., et al., (2013) Biophys. J., 104:139-145.2. Wilhelm, M.J., et al., (2014) Chem. Phys. Lett., 605-606:158-163.

Seasonal variations in some water relations and biochemical attributes of two genetically diverse maize cultivars

Greenhouse (GH) effect has emerged as a major factor in changing cropping patterns and limiting crop yields. This study was conducted to determine the comparative growth and photosynthetic responses of selected heat-resistant (cv. Sadaf) and heat-susceptible (cv. Agatti-2002) cultivars of maize to simulate GH conditions during spring and autumn at seedling, silking, and grain filling stages in 2007. Fifteen day old plants were shifted to plexiglass-fitted canopies to create GH conditions and data were recorded at each growth stage. The results revealed that seasons, GH conditions, and cultivars had large effects on water relations and biochemical attributes. Simulated GH conditions increased the canopy temperature 4–7 °C in spring and 3–5 °C in autumn, but increased relative humidity by 2–3 % in spring and 5–9 % in autumn. Changes in temperature conditions inside the canopy and seasons greatly affected the leaf water, osmotic, and turgor potentials in both cultivars. Temperature variations in both seasons enhanced the production of reactive oxygen species which was evident by increased synthesis of hydrogen peroxide (H2O2), malondialdehyde contents, and increased permeability to ion leakage in both cultivars. Greater free proline accumulation in the tolerant cultivar was marked as a reliable indicator of tolerance to high temperature stress in maize. In addition, Sadaf cultivar was found to be more tolerant than cv. Agatti-2002 in terms of having lower levels of H2O2, MDA contents, and relative membrane permeability.

English

Water stress effects induced by stopping watering at vegetative (S1) and flowering (S2) stages were studied on five varieties of okra [Abelmoschus esculantus Moench (L.)]. Parameters such as relative water content, membrane permeability, chlorophyll content and yield of capsules varieties were evaluated. Our results show that water deficiency reduces relative water content of okra leaves. This reduction is more pronounced when water lack occurs at flowering stage of plants and, leakage of electrolytes across cell membranes is increasing. In addition, soil water deficit increased total chlorophyll content of leaves, which is much higher in stressed plants at vegetative stage. At the vegetative stage as to flowering, water deficit also reduces yield of capsules of varieties UAE 1, UAE 40 and UAE 45. This reduction is much important when plants were stressed at flowering. Key words: Okra, water deficit, physiology, performance.

Overexpression of Glycine soja WRKY20 enhances both drought and salt tolerance in transgenic alfalfa (Medicago sativa L.)

High salinity and drought are major abiotic factors limiting productivity of alfalfa. GsWRKY20 encodes a WRKY-type transcription factor from Glycine soja. In our previous study, heterologous expression of GsWRKY20 in Arabidopsis significantly increased the drought tolerance of Arabidopsis. In order to assess whether GsWRKY20 is also involved in salt stress and breed transgenic forage legume with high drought and salt tolerance, GsWRKY20 was overexpressed in alfalfa. We found that transgenic alfalfa overexpressing GsWRKY20 showed increased drought and salt tolerance. Transgenic alfalfa grew well under high-salinity and water-deficit conditions, while wild-type plants exhibited leaf chlorosis, growth retardation and even death. Lower relative membrane permeability and lower malondialdehyde content were observed in transgenic alfalfa, and more free proline and soluble sugars were accumulated in transgenic alfalfa compared with wild-type plants under high-salinity and water-deficit conditions. Transgenic alfalfa accumulated less Na+ and more K+ in both leaves and roots under high-salinity treatment. In addition, transgenic alfalfa had much thicker cuticle, which could decrease the water loss of plants under water deficit. Taken together, these results reveal an important role for GsWRKY20 in salt and drought stress, and the transgenic alfalfa could be used for farming in salt-affected as well as arid and semi-arid areas.

Short-Time Hypoxia and Post Aeration Alter Relative Membrane Permeability and Total Protein in Root and Leave of Sunflower Cultivars

Aims :There are varieties of factors that results into hypoxia in plant � s root zone. Hypoxia causes oxidative stress and lipid peroxidation, which seriously affect plant growth. In this experiment, effects of hypoxia and post aeration on root and shoot dry weight, relative membrane permeability (RMP) and total protein (TP) of

Over-expressing GsCBRLK/SCMRP Enhances Alkaline Tolerance and Methionine Content in Transgenic Medicago sativa

Drought and saline-alkaline stresses, significantly affect growth and productivity of plants. The reaction of plant to environmental stresses is controlled by numerous genes via transcriptional regulation and protein phosphorylation. A stress-responsive kinase gene, GsCBRLK, has been cloned from a Glycine soja cDNA library under salinity, drought, and cold stresses. Over-expression of GsCBRLK in transgenic Arabidopsis resulted in enhanced tolerance to high salinity and ABA. SCMRP is a kind of storage protein gene coding high-sulfur-containing amino acid. In this study, we constructed an expression vector BEOCBRLK-SCMRP and transformed both GsCBRLK and SCMRP genes into alfalfa. The transgenic alfalfa grew well after NaHCO3 treatment(100 and 150 mmol L–1) for 14 days; whereas, the wild type plants exhibited discoloration and stunted growth, even death. The MDA content and relative membrane permeability caused by alkaline stress in transgenic plants varied significantly compared to those in the wild type(P 0.05). Moreover, the superoxide dismutase(SOD) activity in transgenic plants under alkali stress increased than that of the wild type. Amino acid content assay showed that the transformants had higher methionine content than the non-transformed plants. These results indicated that the transgenic alfalfa carrying both GsCBRLK and SCMRP possesses enhanced alkaline tolerance and rich methionine simultaneously.

Sodium is not required for chloride efflux via chloride/bicarbonate exchanger from rat thymic lymphocytes.

Sodium-dependent Cl−/HCO3 − exchanger acts as a chloride (Cl−) efflux in lymphocytes. Its functional characterization had been described when Cl− efflux was measured upon substituting extracellular sodium (Na+) by N-methyl-D-glucamine (NMDG). For Na+ and Cl− substitution, we have used D-mannitol or NMDG. Thymocytes of male Wistar rats aged 7–9 weeks were used and intracellular Cl− was measured by spectrofluorimetry using MQAE dye in bicarbonate buffers. Chloride efflux was measured in a Cl−-free buffer (Cl− substituted with isethionate acid) and in Na+ and Cl−-free buffer with D-mannitol or with NMDG. The data have shown that Cl− efflux is mediated in the absence of Na+ in a solution containing D-mannitol and is inhibited by H2DIDS. Mathematical modelling has shown that Cl− efflux mathematical model parameters (relative membrane permeability, relative rate of exchanger transition, and exchanger efficacy) were the same in control and in the medium in which Na+ had been substituted by D-mannitol. The net Cl− efflux was completely blocked in the NMDG buffer. The same blockage of Cl− efflux was caused by H2DIDS. The study results allow concluding that Na+ is not required for Cl− efflux via Cl−/HCO3 − exchanger. NMDG in buffers cannot be used for substituting Na+ because NMDG inhibits the exchanger.

Effect of Carbon Monoxide on Active Oxygen Metabolism of Postharvest Jujube

To prolong the shelf life postharvest jujube, the effect of carbon monoxide (CO) on senescence of postharvest jujube in relation to active oxygen metabolism was investigated. Jujubes were fumigated with CO gas at 5, 10, 20 or 40μmol/L for 1 h, and then stored for 30 days at room temperature. Changes in membrane permeability, malonaldehyde (MDA), H2O2, O2•− content, and activities of active oxygen metabolism associated enzymes including superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in fruit were measured. The results indicated that a little of CO could exhibit positive physiological effect on controlling senescence of winter jujube during storage. The study further showed that fumigating jujube fruit with 10 μmol/L CO could reduce increase of MDA content and the relative membrane permeability, effectively inhibit oxidative damage to lipids, decrease H2O2 and O2•− content and maintain high activities of SOD, CAT and POD. The present data suggest that exogenous CO treatment might delay the jujube fruit senescence by regulating active oxygen metabolism.

Effect of Carbon Monoxide Fumigation on the Respiration and Oxidase Activities of Postharvest Jujube

Postharvest jujubes were fumigated with 5, 10, 20 or 40 μmol/L carbon monoxide (CO) for 1 h and then preserved for 30 d at ambient temperature. The effects of CO fumigation on the respiration and oxidase activities of postharvest jujube were determined. Results showed that low CO concentrations (5–10 μmol/L) could restrain the increases of respiration rate, malonaldehyde content, and relative membrane permeability of postharvest jujube. However, high CO concentrations (20–40 μmol/L) showed adverse effects on jujube preservation. Jujube fumigated with 10 μmol/L CO demonstrated optimum effects, and this CO concentration effectively reduced the oxidase activities including lipoxygenase, cytochrome oxidase, polyphenol oxidase and ascorbic oxidase during jujube storage time. As for the reduction of respiration rate and oxidase activities, the delay of membrane lipid peroxidation, fumigating jujube with appropriate concentration of CO might be applied to preserve postharvest jujube and other fruits.

Allelopathic potential of essential oils from four Satureja spp.

Potential damage to human health and to the environment from herbicides is regarded today as a real problem. It has resulted in an increased interest in alternative strategies leading to the development of biodegradable compounds. In this study, allelopathic effects of four essential oils (EOs) of Satureja spp., S. khuzestanica, S. bachtiarica, S. rechingeri and S. spicigera, were investigated against tomato (Lycopersicon esculentum) and rye (Secale cereale). The concentrations 0, 100, 200, 400, 600, 800 and 1000 μl l− 1 of the EOs were tested in vitro against seeds, and their effect on germination, root and shoot length, fresh and dry weight, proline content and relative membrane permeability was determined. EOs from S. khuzestanica and S. rechingeri showed high inhibitory effect against rye and tomato seeds, respectively, at 400 μl l− 1, whereas S. bachtiarica showed the least inhibitory effect on the tested plants. S. spicigera and S. bachtiarica, which significantly decreased rye germination and growth at high concentrations, stimulated the growth at lower concentrations compared with the control treatment. The main components of the examined EOs were carvacrol and thymol. Findings of this study showed that EOs from the tested Satureja species have allelopathic effects on tomato and rye plants and have potential as natural herbicides.

Co-expression of xerophyte Zygophyllum xanthoxylum ZxNHX and ZxVP1-1 enhances salt and drought tolerance in transgenic Lotus corniculatus by increasing cations accumulation.

Lotus corniculatus L. is an important legume for forage, but is sensitive to salinity and drought. To develop salt- and drought-resistant L. corniculatus, ZxNHX and ZxVP1-1 genes encoding tonoplast Na+/H+ antiporter and H+-pyrophosphatase (H+-PPase) from a succulent xerophyte Zygophyllum xanthoxylum L., which is well adapted to arid environments through accumulating Na+ in its leaves, were transferred into this forage. We obtained the transgenic lines co-expressing ZxNHX and ZxVP1-1 genes (VX) as well as expressing ZxVP1-1 gene alone (VP). Compared with wild-type, both VX and VP transgenic lines grew better at 200mM NaCl, and also exhibited higher tolerance and faster recovery from water-deficit stress: these performances were associated with more Na+, K+ and Ca2+ accumulation in their leaves and roots, which caused lower leaf solute potential and thus retained more water. Moreover, the transgenic lines maintained lower relative membrane permeability and higher net photosynthesis rate under salt or water-deficit stress. These results indicate that expression of tonoplast Na+/H+ antiporter and H+-PPase genes from xerophyte enhanced salt and drought tolerance of L. corniculatus. Furthermore, compared with VP, VX showed higher shoot biomass, more cations accumulation, higher water retention, lesser cell membrane damage and higher photosynthesis capacity under salt or water-deficit condition, suggesting that co-expression of ZxVP1-1 and ZxNHX confers even greater performance to transgenic L. corniculatus than expression of the single ZxVP1-1.

Increased drought stress resilience of maize through endophytic colonization by Burkholderia phytofirmans PsJN and Enterobacter sp. FD17

Drought is one of the major environmental stresses that adversely affects crop growth and productivity worldwide. The effect of inoculation of two bacterial endophytes Burkholderia phytofirmans strain PsJN and Enterobacter sp. FD17 on growth, water status and photosynthetic activity of two maize cultivars under drought stress conditions was investigated. Plants were exposed to drought stress by withholding irrigation at vegetative growth stage (45 days after planting). The inoculant strains efficiently colonized maize seedlings and were recovered from root, shoot and leaves of both irrigated and stressed plants. Drought stress had drastic effects on growth, leaf water content and photosynthesis of maize seedlings. Our results revealed that bacterial inoculation minimized the drought stress-imposed effects significantly increasing shoot biomass, root biomass, leaf area, chlorophyll content, photosynthesis, and photochemical efficiency of PSII. Similarly, bacterized seedlings showed higher leaf relative water content (30%) compared to control, whereas 43% higher leaf damage in terms of relative membrane permeability was observed in non-inoculated plants under drought stress. Strain PsJN was more efficient than FD17 in terms of influencing growth and physiological status of the seedlings under drought stress. Our data suggest that maize plants can be protected from inhibitory effects of the drought stress by the harbored bacterial endophytes, although the degree of protection depends on the type of the bacterial strain and the plant genotype.

Cerebroside C increases tolerance to chilling injury and alters lipid composition in wheat roots.

Chilling tolerance was increased in seed germination and root growth of wheat seedlings grown in media containing 20 µg/mL cerebroside C (CC), isolated from the endophytic Phyllosticta sp. TG78. Seeds treated with 20 µg/mL CC at 4°C expressed the higher germination rate (77.78%), potential (23.46%), index (3.44) and the shorter germination time (6.19 d); root growth was also significantly improved by 13.76% in length, 13.44% in fresh weight and 6.88% in dry mass compared to controls. During the cultivation process at 4°C for three days and the followed 24 h at 25°C, lipid peroxidation, expressed by malondialdehyde (MDA) content and relative membrane permeability (RMP) was significantly reduced in CC-treated roots; activities of lipoxygenase (LOX), phospholipid C (PLC) and phospholipid D (PLD) were inhibited by 13.62–62.26%, 13.54–63.93% and 13.90–61.17%, respectively; unsaturation degree of fatty acids was enhanced through detecting the contents of CC-induced linoleic acid, linolenic acid, palmitic acid and stearic acid using GC-MS; capacities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) were individually increased by 7.69–46.06%, 3.37–37.96%, and −7.00–178.07%. These results suggest that increased chilling tolerance may be due, in part, to the reduction of lipid peroxidation and alternation of lipid composition of roots in the presence of CC.