JA-mediated MYC2/LOX/AOS feedback loop regulates osmotic stress response in tea plant

Osmotic stress caused by low-temperature,drought and salinity was a prevalent abiotic stress in plant that severely inhibited plant development and agricultural yield,particularly in tea plant.Jasmonic acid(JA)is an important phytohormone involving in plant stress.However,underlying molecular mechanisms of JA modulated osmotic stress response remains unclear.In this study,high concentration of mannitol induced JA accumulation and increase of peroxidase activity in tea plant.Integrated transcriptome mined a JA signaling master,MYC2 transcription factor is shown as a hub regulator that induced by mannitol,expression of which positively correlated with JA biosynthetic genes(LOX and AOS)and peroxidase genes(PER).CsMYC2 was determined as a nuclei-localized transcription activator,furthermore,ProteinDNA interaction analysis indicated that CsMYC2 was positive regulator that activated the transcription of CsLOX7,CsAOS2,CsPER1 and CsPER3via bound with their promoters,respectively.Suppression of CsMYC2 expression resulted in a reduced JA content and peroxidase activity and osmotic stress tolerance of tea plant.Overexpression of CsMYC2 in Arabidopsis improved JA content,peroxidase activity and plants tolerance against mannitol stress.Together,we proposed a positive feedback loop mediated by CsMYC2,CsLOX7 and CsAOS2 which constituted to increase the tolerance of osmotic stress through fine-tuning the accumulation of JA levels and increase of POD activity in tea plant.

人肺腺癌细胞株A549培养上清液中脂加氧酶活性的证据

已知脂加氧酶(lipoxygenase,EC 1.13.11.12)存在于血小板、白细胞以及肺、脾等组织细胞中,是体内花生四烯酸两条代谢途径之一的关键酶。其产物为羟过氧化二十碳四烯酸(HPETE_s)及白三烯(LT_s)。

Prokaryotic Expression, Purification and Characterization of a Novel Rice Seed Lipoxygenase Gene OsLOX1

Lipoxygenase （LOX, EC1.13.11.12） is a key enzyme during the degradation of lipids in animals and even plants, and also the first key enzyme responsible for the biosynthesis of jasmonate. To purify and characterize the OsLOX1 gene from rice seeds, the entire coding region of the OsLOX1 gene was inserted into an expression vector pET30a（＋） and transformed into Escherichia coil BL21 （DE3）. Expression of the fusion protein was successfully induced by isopropyl-β-D- thiogalactopyranoside （IPTG） and the purified recombinant protein was obtained by His.Bind Kits. Further assay showed that the purified recombinant protein exhibited the LOX activity. The optimum pH was 4.8 （acetate buffer） and the optimum temperature was 30℃ for the above enzyme. Thus, the recombinant might confer an available usage for the synthesis of jasmonate in vitro, and also provides a possibility for elucidating the inter-relationship between the primary structure of the plant seed lipoxygenase protein and its physiological functions.

Eicosanoid pathway in colorectal cancer:Recent updates

Enzymatic metabolism of the 20 C polyunsaturated fatty acid(PUFA) arachidonic acid(AA) occurs via the cyclooxygenase(COX) and lipoxygenase(LOX) pathways, and leads to the production of various bioactive lipids termed eicosanoids. These eicosanoids have a variety of functions, including stimulation of homeostatic responses in the cardiovascular system, induction and resolution of inflammation, and modulation of immune responses against diseases associated with chronic inflammation, such as cancer. Because chronic inflammation is essential for the development of colorectal cancer(CRC), it is not surprising that many eicosanoids are implicated in CRC. Oftentimes, these autacoids work in an antagonistic and highly temporal manner in inflammation; therefore, inhibition of the pro-inflammatory COX-2 or 5-LOX enzymes may subsequently inhibit the formation of their essential products, or shunt substrates from one pathway to another, leading to undesirable side-effects. A better understanding of these different enzymes and their products is essential not only for understanding the importance of eicosanoids, but also for designing more effective drugs that solely target the inflammatory molecules found in both chronic inflammation and cancer. In this review, we have evaluated the cancer promoting and anti-cancer roles of different eicosanoids in CRC, and highlighted the most recent literature which describes how those molecules affect not only tumor tissue, but also the tumor microenvironment. Additionally, we have attempted to delineate the roles that eicosanoids with opposing functions play in neoplastic transformation in CRC through their effects on proliferation, apoptosis, motility, metastasis, and angiogenesis.

12/15-Lipoxygenase inhibition counteracts MAPK phosphorylation in mouse and cell culture models of diabetic peripheral neuropathy

Background: Increased mitogen-activated protein kinase (MAPK) phosphorylation has been detected in peripheral nerve of human subjects and animal models with diabetes as well as high-glucose exposed human Schwann cells, and have been implicated in diabetic peripheral neuropathy. In our recent studies, leukocytetype 12/15-lipoxygenase inhibition or gene deficiency alleviated large and small nerve fiber dysfunction, but not intraepidermal nerve fiber loss in streptozotocin-diabetic mice. Methods: To address a mechanism we evaluated the potential for pharmacological 12/15-lipoxygenase inhibition to counteract excessive MAPK phosphorylation in mouse and cell culture models of diabetic neuropathy. C57Bl6/J mice were made diabetic with streptozotocin and maintained with or without the 12/15-lipoxygenase inhibitor cinnamyl-3,4-dihydroxy-α-cyanocinnamate (CDC). Human Schwann cells were cultured in5.5 mMor30 mMglucose with or without CDC. Results: 12(S) HETE concentrations (ELISA), as well as 12/15-lipoxygenase expression and p38 MAPK, ERK, and SAPK/JNK phosphorylation (all by Western blot analysis) were increased in the peripheral nerve and spinal cord of diabetic mice as well as in high glucose-exposed human Schwann cells. CDC counteracted diabetes-induced increase in 12(S)HETE concentrations (a measure of 12/15-lipoxygenase activity), but not 12/15-lipoxygenase overexpression, in sciatic nerve and spinal cord. The inhibitor blunted excessive p38 MAPK and ERK, but not SAPK/ JNK, phosphorylation in sciatic nerve and high glucose exposed human Schwann cells, but did not affect MAPK, ERK, and SAPK/JNK phosphorylation in spinal cord. Conclusion: 12/15-lipoxygenase inhibition counteracts diabetes related MAPK phosphorylation in mouse and cell culture models of diabetic neuropathy and implies that 12/15-lipoxygenase inhibitors may be an effective treatment for diabetic peripheral neuropathy.

Effects of Lipoxygenase Null Genes of Soybean in Controlling Beany-flavor of Soymilk and Soyflour

The flavor of the soymilk and soyflour obtained from the lipoxygenase mutant isolines was concentrated by simultaneous distillation and extraction (SDE), and its constituents were identified by gas chro-matography (GC) and gas chromatography-mass spectrometry. Results showed that the same 24 flavor constituents were isolated in both soymilk and soyflour, and most of them were aldehydes and alcohols. Lox2 was most responsible for the production of the volatile and beany-flavor components, and Lox1 less responsible. Lox3 was least responsible and can reduce the yield of hexanal. Either Lx1 or Lx2 could significantly reduce the volatile and beany-flavor, and Lx3 could significantly increase the yield of hexanal. Primary and secondary interactions existed among the null mutant genes, and the major effects and interactions could be affected by processing conditions. The isoline with triple lipoxygenase null genes yielded the least volatile and beany-flavor components, and the isoline without the lipoxygenase gene Lx3 produced the greatest amount of the volatile and beany-flavor components. The amounts of volatile and beany-flavor components produced by the other isolines were between that of the isoline with triple lipoxygenase null genes and the isoline without lipoxygenase gene Lx3. According to the correlation analysis, the hexanal amount could be used as an index in evaluating the importance of lipoxygenase isozymes in the yield of beany-flavor compounds, and the effects of the different types of lipoxygenase null mutants in controlling beany-flavor compounds. The cultivars with triple lipoxygenase null genes will be a quality raw material for soy food processing.

Anti-oxidant and anti-inflammatory activity of leaf extracts and fractions of Mangifera indica

Objective:To evaluate the anti-oxidani and anti-inflammatory activity of leaf extracts and fractions of Mangifera indica in in vitro conditions.Methods:In vitro DPPH radical scavenging activity and lipoxygenase（LOX） inhibition assays were used to evaluate the anti-oxidant and anti-inflammatory activities respectively.Methanolic extract（MEMI）,successive water extract （SWMI） and ethyl acetate fraction（EMEMI）,n-butanol fraction（BMEMI） and water soluble fraction （WMEMI） of methanolic extract were evaluated along with respective reference standards. Results:In in ritro DPPH radical scavenging activity,the MEMI,EMEMI and BMEMI have offered significant antioxidant activity with IC50 values of 13.37.3.55 and 14.19μig/mL respectively.Gallic acid,a reference standard showed significant antioxidant activity with IC? value of 1.88 and found to be more potent compared to all the extracts and fractions.In m vitro LOX inhibition assay,the MEMI,EMEMI and BMEMI have showed significant inhibition of LOX enzyme activity with IC50 values of 96.71.63.21 and 107.44μg/mL respectively.While,reference drug Indometlhacin also offered significant inhibtion against LOX enzyme activity with IC50 of 57.75.Furthermore,MEMI was found to more potent than SWMI and among the fractions EMEMI was found to possess more potent antioxidant and anti-inflammatory activity.Conclusions:These findings suggest that the MEMI and F.MEMT possess potent anti-oxidani and anti-inflammatory activities in in vitro conditions.

Emissions of saturated C6-C10 aldehydes from poplar (Populus simonii×P. pyramidalis ‘Opera 8277’) cuttings at different levels of light intensity

Aldehydes play an important role in atmospheric chemistry and plant direct and indirect defense against environmental stresses.In this study,the emissions of saturated C6-C10 aldehydes from Populus simonii × P.pyramidalis ＇Opera 8277＇ cuttings were examined by using a gas chromatography/mass spectrometry（GC/MS） technique at three levels of light intensity（400,800 and 1 200 μmol·m-2·s-1）.A positive correlation between the emissions of these aldehydes and light intensity was found.Moreover,nordi-hydroguaiaretic acid（NDGA）,a special inhibitor of lipoxygenase（LOX）,significantly inhibited the emissions of C6-C9 aldehydes at three levels of light intensity,but did not influence the emission of decanal（C10）.The emissions of C6-C10 aldehydes in NDGA treated poplar cuttings,exhibited the same positive correlation with light intensity.The results indicated that LOX pathway contributes to the emissions of C6-C9 aldehydes,whereas some pathways regulated by light intensity might be a universal mechanism for emissions of C6-C10 aldehydes.

Synergistic Influence of Pre-Harvest Calcium Sprays and Postharvest Hot Water Treatment on Fruit Firmness, Decay, Bitter Pit Incidence and Postharvest Quality of Royal Delicious Apples (<i>Malus x domestica</i>Borkh)

Experiments were conducted to observe the effect of pre-harvest calcium (Ca) applied as calcium chloride (1% W/V) and postharvest hot water treatment (HWT) on “Royal Delicious” apples. For this, apples were divided in 4 lots viz., untreated (neither Ca nor HWT), Ca alone (pre-harvest 3 sprays of CaCl2 (1.0% w/v) in the orchard), HWT (42℃ for 2 h). Apples of all four lots were stored in cold storage maintained at 0℃ ± 1℃ and 90% - 95% relative humidity for 6 months. After storage, fruits were removed to ambient conditions for 5 days, and then observations on decay area and incidence, bitter pit incidence, fruit Ca content, lipoxygenase (LOX) and antioxidant (AOX) activity, fruit firmness and fruit quality parameters were recorded. After 6 months in cold storage plus 5 day at 22℃ ± 2℃ and 70% + 4% RH, apples, which received Ca as pre-harvest spray or those which received postharvest hot water treatment or Ca + HWT had significantly lesser decay area (decay lesions) caused by Penicillium expansum or Botrytis cinerea than untreated ones (control). Ca + HWT treatment was significantly more effective on B. cinerea than P. expansum. Untreated apples exhibited higher incidence of bitter pit (18.2%) than those treated with Ca or HWT or both. Fruit Ca content (2.92% DM) were significantly lower and conversely the LOX activity (6.9 μmoles min–1×g–1FW) was higher in untreated apples. Similarly, total phenolics and AOX activity were also lower in the untreated apples than Ca or HWT treated. HWT or Ca treated apples have beneficial effects on fruit firmness, peel colour and quality parameters like TSS and ascorbic acid content. Thus, it is concluded that pre-harvest sprays of calcium chloride with postharvest HWT is highly useful for “Royal Delicious” for reducing decay loss, maintaining firmness, high levels of antioxidants and fruit quality.

Response dynamics of three defense related enzymes in cotton leaves to the interactive stress of Helicoverpa armigera (Hübner) herbivory and omethoate application

In order to explore the response dynamics of the activities of defense related enzymes in cotton leaves towards the interactive stress of Helicoverpa armigera herbivory and omethoate application, the activities of phenylalanine ammonia-lyase（PAL）, lipoxygenase（LOX）, and polyphenol oxidase（PPO） were examined from 6 to 126 h after cotton leaves were treated 12 h of H. armigera herbivory, and then sprayed with 800 mg L–1 omethoate. The results showed that the changes in the activities of PAL, LOX and PPO that occured under the interactive stress of H. armigera herbivory and omethoate application reflected the interactive effects of the two stresses on cotton defense. The similarity between the response dynamics of PAL, LOX, and PPO activities in cotton leaves under the interactive stress and that under H. armigera herbivory treatment alone showed that the induction of H. armigera herbivory on the activities of PAL, LOX and PPO in cotton leaves played a leading role in the interactive effects, and the effect of omethoate application played only a minor role. A joint factor analysis was performed according to a method which has been used to analyze the joint toxicity of pesticides; this analysis sought to clarify if there was a synergistic, antagonistic, or additive effect on PAL, LOX, and PPO activity in cotton leaves resulting from the interactive H. armigera herbivory and omethoate treatment. In the interactive effect on the response of PAL activity in cotton leaves, antagonistic effects of the omethoate application towards H. armigera herbivory were observed at 6 and 12 h. Synergistic effects were then observed at 18 and 30 h. Antagonistic effects were observed from 54 to 78 h and synergistic effects were finally observed at 126 h. The correlation between H. armigera herbivory and omethoate application in the interactive effect on cotton defense responses of LOX activity also fluctuated from synergism to antagonism during the time course. In the interactive effect on PPO activity, only antagonism was observed between H. armigera herbivory and omethoate application. In the interactive stress of H. armigera herbivory and omethoate application on cotton defense responses, omethoate affected the defense responses of cotton to H. armigera herbivory by producing antagonistic and synergistic effects. These results will be useful to understand the relationship between host plant and herbivorous pest.

Purification and characterization of lipoxygenase from Entermorpha clathrata

The purification and characterization of lipoxygenase （LOX, EC 1.13.11.12） from the green algae Enteromorpha clathrata were studied. Two components marked LOX - 1 and LOX - 2 were purified and their molecular masses were estimated to be 102 and 79 ku by SDS - PAGE. Both LOX - 1 and LOX - 2 were stable over the pH wide range 6.0 - 10.0 and had the optimum pH of 10.0 and 8.6, at optimum temperature of 30 and 25℃, respectively. Substrate specificities of LOX - 1 and LOX - 2 were the greatest towards linoleic acid, followed by arachidonic acid and linolenic acid. The Michaelis constant values of LOX - 1 and LOX - 2 were 0.23 and O. 20 mmol/dm^3 with the substrate of linoleic acid. The LOX activities were stimulated greatly by Ca^2＋ but inhibited by Hg2 ~ and the antioxidants such as BHA, BHT and TBHQ. The hydroperoxide products of LOX were analysed by HPLC with the substrate of methyl linoleate, and the results showed that LOX - 1 formed mainly 9-hydroperoxides while LOX - 2 formed both 9- and 13-hydroperoxides at a ratio of 24： 76.

Genome-wide identification and characterization of the abiotic-stress-responsive lipoxygenase gene family in diploid woodland strawberry(Fragaria vesca)

Lipoxygenase(LOXs)is a kind of dioxygenase without heme and iron,which plays an important role in the development and adaptation of many plants to the environment.However,the study of strawberry LOX gene family has not been reported.In this study,14 LOX genes were identified from the diploid woodland strawberry genome.The phylogenetic tree divides the FvLOX gene into two subfamilies:9-LOX and 13-LOX.Gene duplication event analysis showed that whole-genome duplication(WGD)/segmental duplication and dispersed duplication effectively promoted the expansion of strawberry LOX family.QRT-PCR analysis showed that FvLOX genes were expressed in different tissues.Expression profile analysis showed that FvLOX1 and FvLOX8 were up-regulated under low temperature stress,FvLOX3 and FvLOX7 were up-regulated under drought stress,FvLOX6 and FvLOX9 were up-regulated under salt stress,FvLOX2,FvLOX3 and FvLOX6 were up-regulated under salicylic acid(SA)treatment,FvLOX3,FvLOX11 and FvLOX14 were up-regulated under methyl jasmonate(MeJA)treatment,FvLOX4 and FvLOX14 were up-regulated under abscisic acid(ABA)treatment.Promoter analysis showed that FvLOX genes were involved in plant growth and development and stress response.We analyzed and identified the whole genome of strawberry FvLOX family and characterized a variety of FvLOX candidate genes involved in abiotic stress response.This study laid a theoretical and empirical foundation for the response mechanism of strawberry to abiotic stress.

Detection of RAPD Markers Linked to Gene lx_1 in Soybeans

Near-isogenic lines of soybean lipoxygenase, which contain genes Lox, lx1, lx2, lx3, lx1.3, lx2.3,respectively, were used for polymorphic analysis by RAPD technique.520 10-mer-oligonucleotideprimers were screened, and thirteen primers showed polymorphism among near-isogenic lines.There were six primers showed special polymorphic bands among lines lx1 and lx1.3. Especially,primer S352 presented the stable results in which a 900 bp band was found in the lines lx1 andlx1.3, and primer S352900 was detected with F2 generation of cross 96P11×Century-1, indicatedprimer S352900 could be identified as a RAPD marker linked to gene lx1 in soybeans, the distanceof linkage was 7.6 cM.

A Facile Total Synthesis of 2-Geranyl-2',3,4',4-tetrahydroxydihydrochalcone with Highly 5-Lipoxygenase Inhibiting Activity

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Effects of abiotic stress and hormones on the expressions of five13-CmLOXs and enzyme activity in oriental melon(Cucumis melo var.makuwa Makino)

Lipoxygenases（LOXs） are a group of non-heme,iron-containing enzymes and extensively involved in plant growth and development,ripening and senescence,stress responses,biosynthesis of regulatory molecules and defense reaction.In our previous study,18 LOXs in melon genome were screened and identified,and five 13-LOX genes（CmLOX08,CmLOX10,CmLOX12,CmLOX13 and CmLOX18） were predicted to locate in chloroplast.Phylogenetic analysis result showed that the five genes have high homology with jasmonic acid（JA） biosynthesis-related LOXs from other plants.In addition,promoter analysis revealed that motifs of the five genes participate in gene expression regulated by hormones and stresses.Therefore,we analyzed the expressions of the five genes and LOX activity in leaves of four-leaf stage seedlings of oriental melon cultivar Yumeiren under abiotic stress：wounding,cold,high temperature and hydrogen peroxide（H_2O_2）,and signal molecule treatments：methyl jasmonate（MeJA）,abscisic acid（ABA） and salicylic acid（SA）.Real time qPCR revealed that wounding and H_2O_2 induced the expressions of all the five genes.Only CmLOX08 was induced by cold while only CmLOX13 was suppressed by high temperature.ABA induced the expressions of CmLOXIO and CmLOX12 while inhibited CmLOX13 and CmLOX18.MeJA increased the 3 genes expressions except CmLOX08 and CmLOX13,whereas SA decreased the effect,apart from CmLOX12.All the abiotic stresses and signal molecules treatments increased the LOX activity in leaves of oriental melon.In summary,the results suggest that the five genes have diverse functions in abiotic stress and hormone responses,and might participate in defense response.The data generated in this study will be helpful in subcellular localization and transgenic experiment to understand their precise roles in plant defense response.

Soybean Improvement for Lipoxygenase-free by Simple Sequence Repeat(SSR)Markers Selection

Beany flavor of soybean(Glycine max(L.)Merr.)is caused by oxidation of polyunsaturated fatty acids by the action of three lipoxygenases(LOX1,LOX2 and LOX3)present in mature seeds.The unpleasant flavor restricts human consumption of soybean products.This problem could be solved through genetic elimination of alleles that code these enzymes.Parental cultivars and two hybrid population were selected and analyzed using genetic markers for alleles locus,encoding L_(ox1),L_(ox2)and L_(ox3)free.The SSR marker Satt 212 confirmed the presence of the homozygous null-allele L_(x3)in the cultivar BRS 213,which were used for hybridization with BR 36.Heterozygote F1 hybrid plants and homozygous L_(x3)lines in F_(2)segregating populations were successfully identified.The SSR markers Sat090 and Sat417 were the most effective diagnostic markers among all SSR markers tested.Satt090 and Satt417 confirmed the presence of the homozygous L_(x2)null-allele in the parental cultivar BRS 213 by flanking L_(x2)loci at 3,00 and 2,77 cM,respectively.The presence of L_(x2)null allele in the F_(2)segregating populations between BRS 213 and BRS 155 was successfully identified with a selection efficiency of 98%and have great potential for further application in the Brazilian breeding program aimed at improving soybean seed quality.

Formation of (2E)-4-Hydroxy-2-nonenal and (2E)-4-Hydroxy-2-hexenal by Plant Enzymes: A Review Suggests a Role in the Physiology of Plants

It is demonstrated that (3Z)-nonenal (NON) and (3Z)-hexenal (HEX) are oxidized in a cascade by lipoxygenase (LOX) and hydroperoxide peroxygenase (HP peroxygenase) into (2E)-4-hydroxy-2- nonenal (HNE) and (2E)-4-hydroxy-2-hexenal (HHE), respectively. In turn, HNE inactivates LOX terminating the cascade. The hydroxy-alkenals produced serve to inhibit plant pathogens, which initiated the cascade. In addition to LOX, other unknown oxygenases may be involved in the cascade.

Hyperhomocysteinemia dysregulates plasma levels of polyunsaturated fatty acids-derived eicosanoids

Hyperhomocysteinemia(HHcy)contributes to the incidence of many cardiovascular diseases(CVD).Our group have previously established crucial roles of eicosanoids and homocysteine in the incidence of vascular injury in diabetic retinopathy and renal injury.Using cystathionine-β-synthase heterozygous mice(cβs^(+/-))as a model of HHcy,the current study was designed to determine the impact of homocysteine on circulating levels of lipid mediators derived from polyunsaturated fatty acids(PUFA).Plasma samples were isolated from wild-type(WT)and cβs^(+/-)mice for the assessment of eicosanoids levels using LC/MS.Plasma 12/15-lipoxygenase(12/15-LOX)activity significantly decreased in cβs^(+/-)vs.WT control mice.LOX-derived metabolites from both omega-3 and omega-6 PUFA were also reduced in cβs^(+/-)mice compared to WT control(P<0.05).Contrary to LOX metabolites,cytochrome P450(CYP)metabolites from omega-3 and omega-6 PUFA were significantly elevated in cβs^(+/-)mice compared to WT control.Epoxyeicosatrienoic acids(EETs)are epoxides derived from arachidonic acid(AA)metabolism by CYP with anti-inflammatory properties and are known to limit vascular injury,however their physiological role is limited by their rapid degradation by soluble epoxide hydrolase(sEH)to their corresponding diols(DiHETrEs).In cβs^(+/-)mice,a significant decrease in the plasma EETs bioavailability was obvious as evident by the decrease in EETs/DiHETrEs ratio relative to WT control mice.Cyclooxygenase(COX)metabolites were also significantly decreased in cβs^(+/-)vs.WT control mice.These data suggest that HHcy impacts eicosanoids metabolism through decreasing LOX and COX metabolic activities while increasing CYP metabolic activity.The increase in AA metabolism by CYP was also associated with increase in sEH activity and decrease in EETs bioavailability.Dysregulation of eicosanoids metabolism could be a contributing factor to the incidence and progression of HHcy-induced CVD.

Responses of phospholipase D and lipoxygenase to mechanical wounding in postharvest cucumber fruits

This study was to investigate the responses of phospholipase D(PLD) and lipoxygenase(LOX) to mechanical wounding in postharvest cucumber(Cucumis sativus L.cv.Biyu-2) fruits.Membrane-associated Ca2+ content,activities and gene expression of PLD and LOX,and contents of phosphatidylcholine(PC),phosphatidylinositol(PI),and phosphatidic acid(PA) were determined in cucumber fruits following mechanical wounding.Results show that PLD and LOX activities increased with the PLD and LOX mRNAs which are upregulated upon wounding,while membrane-associated Ca2+ content decreased.Accompanying with the increase of PLD and LOX activities,accumulation of PA and losses of PC and PI were observed in all fruits,but there were differences of degrees between wounded and control fruits.Results suggest that PLD and LOX might be the main hydrolytic enzymes of phospholipids in postharvest cucumber fruits participating in the mechanical wounding injury.The activation of PLD and LOX might be the result of gene expression,which could be stimulated by the Ca2+ flowing from the membrane to the cytoplasm upon receiving the wounding signals.