2,4-二硝基苯酚对采后龙眼果皮脂氧合酶活性和膜脂脂肪酸组分的影响

以'福眼'龙眼(Dimocarpus longan Lour.'Fuyan')果实为材料,研究呼吸解偶联剂2,4-二硝基苯酚(DNP)对采后果皮脂氧合酶(LOX)活性、膜脂脂肪酸组分和细胞膜透性的影响及其与果皮褐变的关系.结果表明:DNP处理导致龙眼果皮细胞膜透性、LOX活性和褐变指数增加,膜脂脂肪酸组分中的棕榈酸(C16:0)、硬脂酸(C18:0)等饱和 脂肪酸的组分增加,亚油酸(C18:2)、亚麻酸(C18:3)和花生一烯酸(C20:1)等不饱和脂肪酸的组分下降,脂肪酸不饱和指数和脂肪酸不饱和度下降.因此认为,DNP促进了龙眼果实果皮褐变可能是由于提高了LOX活性,促进了膜脂不饱和脂肪酸的降解而引起膜系统完整性受损,最终导致细胞膜结构的破坏,使酚酶与酚类物质接触而引起酚类物质氧化的结果.     

Lipoxygenase from cucumber fruit: Localization and properties

The subcellular localization of lipoxygenase (LOX) from cucumber fruit has been studied. Two methods have been employed to obtain organelles; (1) maceration of the tissue, followed by separation on a linear sucrose gradient and (2) release from protoplasts by osmotic shock, followed by a discontinuous Ficoll gradient. It was possible to obtain high LOX activity in the intact protoplasts from both peel and flesh tissue. However, fewer intact vacuoles were obtained following osmotic rupture than from macerated tissue. Both methods produced more particulate LOX activity from the peel than from flesh tissue, and both showed that this activity was associated with the vacuoles. The cucumber LOX enzyme was similar to the potato and tomato enzymes, both in pH characteristics and substrate specificity.     

Lipolytic and peroxidative enzyme expressions in cultured potato tuber cells

Potato cells (cv. Norchip) were cultured from tuber parenchymal tissue and subcultured to dissociate and habituate the despecialized cells. After several subculturings on a minimal nutrient media, this line of cells demonstrated repeatable physical growth profiles for dry weight (DW), fresh weight (FW) and protein. Two enzymes of plant lipid metabolism were investigated, lipolytic acyl hydrolase (LAH) and lipoxygenase (LOX), which respectively liberate and peroxidize fatty acids from lipid in cellular membranes. LAH, measured as p-nitrophenyl palmitate hydrolase, was present in this line of cells in easily detectable amounts (317 units g^-1 DW) albeit much lower than that found in mother tuber (9878 units g^-1 DW). The presence of LAH in this line is significant because LAH isozymes are often described as storage proteins, yet activity per gram fresh weight in these unorganized cells is reasonably constant until culture growth exits the linear phase. However, LOX, the most active free fatty acid metabolizing enzyme in potato tubers (89,800 units g^-1 DW), was not detectable in this line of callus or suspension cultured cells. The absence of LOX activity in this line of cells was verified by a number of assay approaches and was confirmed by activity staining of extracted enzymes separated in polyacrylamide gels. The absence of LOX in these cultured cells is especially important in determining the functions of this lipid peroxidation system and how it may be genetically regulated.Mention of company or trade name does not imply endorsement by the United States Department of Agriculture over others not named.A laboratory cooperatively operated by the Midwest Area, Agricultural Research Service, U.S. Department of Agriculture, The Minnesota Agricultural Experiment Station, the North Dakota Agrcultural Experiment Station, and the Red River Valley Potato Grower's Association.     

钙处理对红富士苹果酶促褐变的影响

渗钙处理能够明显保持红富士苹果的硬度,且褐变度明显低于对照,渗钙对酶促褐变的抑制作用是通过影响PPO活性和LOX活性起作用的,果实褐变的早期发动与LOX活性相关密切,后期褐变则主要是PPO起作用。     

高温强光胁迫对苹果果皮PPO活性的影响

苹果果实日烧是一种普遍发生的生理病害,最常见的特征之一就是在果实表面出现褐变。通常认为PPO与植物的酶促褐变密切相关。研究了自然和控制条件下,高温强光胁迫对果实PPO活性的影响,以便揭示高温强光胁迫下苹果果实褐变与PPO活性之间的联系。结果表明：高温和强光胁迫与果皮PPO活性变化密切相关。就树冠不同方位而言,西南方位是高温和强光胁迫最严重的区域,其外围裸露果实的PPO活性也最强。在一定范围内,随着处理温度和光照强度的升高,果皮PPO活性也逐渐增强。短时间剧烈升温能够引起PPO活性骤然上升。在同样程度的高温胁迫下,提高环境湿度有利于抑制果皮PPO活性,从而减轻褐变症状的发生。室内外试验一致证实：果实日烧褐变现象与高温强光胁迫下果皮组织PPO活性大幅度提高有直接关系。     

Phenolic Content Pattern, Polyphenol Oxidase and Lipoxygenase Activity in Relation to Albinism, Fruit Malformation and Nubbins Production in Strawberry (Fragaria x ananassa Duch)

Total phenol content, polyphenol oxidase (PPO) and lipoxygenase (LOX) activity were determined in strawberry fruits to establish a relationship between phenolic content, PPO and LOX activity with the production of abnormal fruits in 10 different strawberry cultivars. The study revealed that all strawberry cultivars produced abnormal fruits in varying proportion. Highest percentage of abnormal fruits was produced by Etna (21.8%), and the lowest by Senga Sengana (3.7%). Among cultivars, Etna produced maximum percentage of albino (25.8%), malformed (22.7%) or nubbin (button) berries (16.9%), while the lowest percentage of albino (5.2%), and malformed fruits (2.5%) were produced by Senga Sengana, and nubbin (button) (2.9%) by Camarosa. Total phenol content and PPO and LOX activity varied widely among different strawberry cultivars. The highest phenol content was recorded in Senga Sengana (14.4 mg g^?1, fresh tissue weight) and the minimum in Etna (3.1 mg g^?1 fresh tissue weight). Likewise, Etna exhibited the minimum PPO activity (0.503 ΔA₄₀₀ g^?1 min^?1) and Senga Sengana, the maximum (0.732 ΔA₄₀₀ g^?1 min^?1). Similarly, normal fruits exhibited higher PPO activity (0.753 ΔA₄₀₀ g^?1 min^?1) than abnormal fruits. The highest LOX activity was exhibited by Senga Sengana (0.462 μ katal kg^?1) and the lowest by Etna (0.338 μ katal kg^?1) Similarly, LOX activity was very high in normal fruits (0.568 μ katal kg^?1) in comparison to abnormal ones. The regression equations developed between total phenol content, PPO and LOX activity with abnormal fruits revealed that an inverse relationship existed between total phenol content, PPO and LOX activity and production of abnormal fruits in strawberry.     

RNAi mediated silencing of lipoxygenase gene to maintain rice grain quality and viability during storage

Lipoxygenase (LOX) is a common enzyme which catalyzes lipid peroxidation of seeds and consequently enhances seed quality deterioration and decreases seed viability. During seed storage, peroxidation of unsaturated fatty acids occur due to enhancement of LOX activity which directly leads to reduction in seed vigour and deterioration of grain nutritional quality. This study was undertaken to overcome these problem during rice seed storage by attenuating LOX activity using RNAi technology. To improve seed storage stability, we down regulated LOX gene activity by using a functional fragment of the LOX gene under the control of both constitutive (CaMV35S) and aleurone-specific (Oleosin-18) promoter separately. To understand the storage stability, RNAi–LOX seeds and non-transgenic control seeds were subjected to accelerated aging at 45 °C and 85 % relative humidity for 14 days. Our studies demonstrate that down regulation of LOX activity reduces the seed quality deterioration under storage condition. In addition GC–MS analysis revealed that reduction of fatty acid level in non-transgenic seeds during storage was higher when compared with that of transgenic rice seeds. Furthermore, the transgenic rice seeds with reduced LOX activity exhibited enhanced seed germination efficiency after storage than that of non-transgenic rice seeds. This study will have direct impact on nutritional stability of quality rice grains.     

Lysyl oxidase polymorphisms and susceptibility to osteosarcoma

Despite the knowledge of many genetic alterations present in osteosarcoma, the complexity of this disease precludes placing its biology into a simple conceptual framework. Lysyl oxidase (LOX) catalyzes the cross-linking of elastin and collagen, which is essential for the structural integrity and function of bone tissue. In the current study, we performed genomic sequencing on all seven exons -including the intron-exon splice sites, and the putative promoter region of LOX gene - followed by luciferase reporter assay to analyze the function of newly identified polymorphisms. Associations between LOX polymorphisms and osteosarcoma were then evaluated. Our sequencing data revealed three polymorphisms (−22G/C, 225C/G, and 473G/A) in the exons and promoter region of LOX. The −22G/C polymorphism lies in the downstream core promoter element (DPE) region and caused a decrease in promoter activity of LOX. The prevalence of the −22C allele and 473A allele were significantly increased in osteosarcoma patients compared to controls (odds ratio [OR] = 3.88, 95% confidence interval [CI]  = 1.94−7.78, p = 4.18×10⁻⁵, and OR = 1.38, 95%CI = 1.07−1.78, p = 0.013; p 0.0167 was considered significant after Bonferroni correction). Analyzing haplotype showed that the frequency of CCG haplotype (−22, 225, 473) was significantly higher in osteosarcoma cases than in healthy controls after Bonferroni correction (p = 4.46×10⁻⁴). These results indicate that the −22G/C polymorphism may affect the expression of LOX, and that −22G/C and 473G/A polymorphisms may be new risk factors for osteosarcoma. These findings reveal a potential new pathway by which genetic polymorphisms may affect human diseases.     

Peptides derived from the copper‐binding region of lysyl oxidase exhibit antiangiogeneic properties by inhibiting enzyme activity: an in vitro study

Despite the rigorous research on abnormal angiogenesis, there is a persistent need for the development of new and efficient therapies against angiogenesis‐related diseases. The role of Lysyl oxidase (LOX) in angiogenesis and cancer has been established in prior studies. Copper is known to induce the synthesis of LOX, and hence regulates its activity. Hypoxia‐induced metastasis is dependent on LOX expression and activity. It has been believed that the inhibition of LOX would be a therapeutic strategy to inhibit angiogenesis. To explore this, we designed peptides (M peptides) from the copper‐binding region of LOX and hypothesized them to modulate LOX. The peptides were characterized, and their copper‐binding ability was confirmed by mass spectrometry. The M peptides were found to reduce the levels of intracellular copper when the cells were co‐treated with copper. The peptides showed promising effect on aortic LOX, recombinant human LOX and LOX produced by human umbilical vein endothelial cells (HUVECs). The study also explores the effect of these peptides on copper and hypoxia‐stimulated angiogenic response in HUVECs. It was found that the M peptides inhibited copper/hypoxia‐induced LOX activity and inhibited stimulated HUVEC tube formation and migration. This clearly indicated the potential of M peptides in inhibiting angiogenesis, highlighting their role in the formulation of drugs for the same. Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd.     

Jasmonates modulate the promotion effects induced by SNP on root development of wheat under osmotic stress through lipoxygenase activation

We investigated promotion effects of exogenous sodium nitroprusside (SNP) on wheat seedling (Triticum aestivum L.) lateral root (LR) and root hair development, and the relationship between endogenous jasmonate (JA) production and activity changes of lipoxygenase (LOX) isoenzymes under osmotic stress generated by 15 % PEG-6000. Our results showed that 25 or 50 μM SNP could significantly increase LR length and number whether or not the seedlings were under PEG stress. When 50 μM cPTIO, 50 μM SHAM or 50 μM NDGA was supplemented, the promotion effects of SNP were blocked. SNP could also induce the production of endogenous JAs in roots, and 25 μM SNP induced the maximum JA content. The effect of SNP on JA production could also be blocked by adding cPTIO, SHAM or NDGA. Furthermore, the activity of lipoxygenase (LOX) in roots was affected by SNP; the maximal activity of LOX also occurred in the roots treated by 25 μM SNP under PEG stress, or 50 μM SNP without PEG stress. LOX isoenzymes in roots were detected by electrophoresis; the results showed that 25 μM SNP could noticeably increase the activities of LOXII and LOXIII under PEG stress. Our results suggest that, under osmotic stress generated by PEG, the promotion effects of exogenous SNP on wheat LR and root hair development could be mediated by endogenous JAs through LOX activation.     

Citrus abscission and Arabidopsis plant decline in response to 5-chloro-3-methyl-4-nitro-1H-pyrazole are mediated by lipid signalling

The compound 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMNP) is a pyrazole-derivative that induces abscission selectively in mature citrus (Citrus sinensis) fruit when applied to the canopy and has herbicidal activity on plants when applied to roots. Despite the favourable efficacy of this compound, the mode of action remains unknown. To gain information about the mode of action of CMNP, the effect of application to mature citrus fruit and Arabidopsis thaliana roots was explored. Peel contact was essential for mature fruit abscission in citrus, whereas root drenching was essential for symptom development and plant decline in Arabidopsis. CMNP was identified as an uncoupler in isolated soybean (Glycine max) mitochondria and pea (Pisum sativum) chloroplasts and an inhibitor of alcohol dehydrogenase in citrus peel, but not an inhibitor of protoporphyrinogen IX oxidase. CMNP treatment reduced ATP content in citrus peel and Arabidopsis leaves. Phospholipase A₂ (PLA₂) and lipoxygenase (LOX) activities, and lipid hydroperoxide (LPO) levels increased in flavedo of citrus fruit peel and leaves of Arabidopsis plants treated with CMNP. An inhibitor of PLA₂ activity, aristolochic acid (AT), reduced CMNP-induced increases in PLA₂ and LOX activities and LPO levels in citrus flavedo and Arabidopsis leaves and greatly reduced abscission in citrus and delayed symptoms of plant decline in Arabidopsis. However, AT treatment failed to halt the reduction in ATP content. Reduction in ATP content preceded the increase in PLA₂ and LOX activities, LPO content and the biological response. The results indicate a link between lipid signalling, abscission in citrus and herbicidal damage in Arabidopsis.     

Involvement of lipoxygenase in elicitor-stimulated sanguinarine accumulation in Papaver somniferum suspension cultures

The involvement of lipoxygenase (LOX, EC 1.13.11.12) in elicitor-induced opium poppy defense response was investigated. Papaver somniferum L. suspension cultures were treated with abiotic elicitor methyl jasmonate (MJ), fungal elicitor (Botrytis cinerea homogenate) and phenidone (specific inhibitor of LOX) to determine the involvement of this enzyme in production of sanguinarine, the major secondary metabolite of opium poppy cultures. P. somniferum suspension cultures responded to elicitor treatment with strong and transient increase of LOX activity followed by sanguinarine accumulation. LOX activity increased in elicited cultures, reaching 9.8 times of the initial value at 10 h after MJ application and 2.9 times after B. cinerea application. Sanguinarine accumulated to maximal levels of 169.5 ± 12.5 μg g^?1 dry cell weight in MJ-elicited cultures and 288.0 ± 10.0 μg g^?1 dry cell weight in B. cinerea-elicited cultures. The treatment of cells with phenidone before elicitor addition, significantly reduced sanguinarine production. The relative molecular weight of P. somniferum LOX (83 kDa) was estimated by using immunobloting and its pH optimum was shown to be pH 6.5.     

PRO-LONG涂膜对采后贮藏荔枝果实色泽和酶活性变化的影响

本文以荔枝品种“槐枝”为材料,以1．5％和2．5％Pro-long涂膜处理果实,研究Pro-long涂膜对果后贮于4℃的荔枝果皮色泽变化和有关酶活性的变化。对照和处理的HunterL值和b值均随贮藏时间的延长而降低,处理的比对照的下降慢。采后贮藏开始21d内,对照和处理的HuntCra值变化很小,保持相对稳定,之后的贮藏时间内有较显著的下降,说明贮藏初期果实的红色特性变化较少,之后变化很明显,这与果皮花色素苷、类黄酮、总酚的变化是相对应的。在贮藏后期,处理的HuntCra值下降明显较对照慢。Hunter值的变化与在贮藏过程中果实外观逐渐变成暗红和揭变以及在果实的来后根变中起着重要作用的多酚氧化酶和部分地涉及褐变过程的过氧化物酶的变化相对应。处理的过氧化物酶活性增加较对照慢,而且,与对照比较,多酚氧化酶的峰值稍稍延迟了。未发现l‘5％和2．5％处理间有明显差别。因此,Pro-long涂胶对荔枝的应用可以部分地降低多酚氧化酶和过氧化物酶,影响果皮花色素苷的降解、类黄酮和总酚的变化,延迟了褐变过程的发生。     

Whole fruit staining with aniline blue at harvest is associated with superficial pathogenesis of “Fuji” apples after storage

Abstract

Whole “Fuji” apples (Malus domestica Borkh cv. Fuji) were treated with 0.2% aniline blue before storage in 2006, 2007 and 2008 to determine whether cuticular microcracking was associated with post-storage disorders. After storage for 7 months at 0° C and 90% relative humidity followed by 3 days at 20° C, a higher aniline blue staining scale value was associated with a higher peel browning and decay index. These results indicate that superficial disorders or diseases of apples may be related to cuticular microcracking that can be seen by aniline blue staining. Scanning electron microscopy was used to analyze the ultrastructure of stained portions of the cuticular complex. Disorders or diseases of the cuticle of epidermal tissue was associated with cracked lenticels, unhealed microcracks around the edge of the lenticel, and collapsed epicuticular wax; these areas stained more intensely. Our results indicated the potential of using an aniline blue staining prior to storing the fruit to predict the ultimate quality.     

荔枝果皮结构与果实贮藏性能关系的探讨

在荔枝淮枝品种果实贮藏中进行单果失重率的测定,并通过扫描电子显微镜对鲜果、褐变果、霉变果的果皮进行显微结构的观察,发现荔枝果实外果皮细胞形态结构特殊,向外突出成半球形并和栅状组织一样极易破损失水而加速果皮的褐变。褐变前、霉变前后果实失重率大。电镜下观察霉变果实表面布满着酵母和其它菌体,真菌菌丝侵入果皮内生长繁殖,破坏栅状组织等,是导致果实迅速霉烂的原因之一     

Antisense suppression of LOX3 gene expression in rice endosperm enhances seed longevity

Lipid peroxidation plays a major role in seed longevity and viability. In rice grains, lipid peroxidation is catalyzed by the enzyme lipoxygenase 3 (LOX3). Previous reports showed that grain from the rice variety DawDam in which the LOX3 gene was deleted had less stale flavour after grain storage than normal rice. The molecular mechanism by which LOX3 expression is regulated during endosperm development remains unclear. In this study, we expressed a LOX3 antisense construct in transgenic rice (Oryza sativa L.) plants to down‐regulate LOX3 expression in rice endosperm. The transgenic plants exhibited a marked decrease in LOX mRNA levels, normal phenotypes and a normal life cycle. We showed that LOX3 activity and its ability to produce 9‐hydroperoxyoctadecadienoic acid (9‐HPOD) from linoleic acid were significantly lower in transgenic seeds than in wild‐type seeds by measuring the ultraviolet absorption of 9‐HPOD at 234 nm and by high‐performance liquid chromatography. The suppression of LOX3 expression in rice endosperm increased grain storability. The germination rate of TS‐91 (antisense LOX3 transgenic line) was much higher than the WT (29% higher after artificial ageing for 21 days, and 40% higher after natural ageing for 12 months). To our knowledge, this is the first report to demonstrate that decreased LOX3 expression can preserve rice grain quality during storage with no impact on grain yield, suggesting potential applications in agricultural production.     

Detection and Isolation of Preformed Antifungal Compounds from the Peel of Pyrus bretschneideri Rehd. cv. Pingguoli at Different Stages of Maturity

Ethanol‐dichloromethane crude extract from peel of pear (Pyrus bretschneideri Rehd. cv. Pingguoli) was separated by thin layer chromatographic plates and bioassayed with conidia of Alternaria alternata. The inhibition zones differed significantly in retention factor (R_f) at expanding stage, harvest time and after 100 days of cold storage. The compounds in the inhibition zones were isolated and identified with gas chromatography and mass spectroscopy. Palmitate methyl, oleic acid methyl, linolenic acid methyl and squalene were present at all stages. The concentration of these chemicals was the highest in expanding stage fruit peel and decreased rapidly with fruit development. It is suggested that these compounds may be the main antifungal compounds in the growing fruit. The phthalate alkyl esters occurred at relatively higher concentrations in pear peel at harvest and after 100 days of cold storage. Six phthalate alkyl esters were identified from peel of pear fruit after 100 days of cold storage. It is also supposed that these esters may be the antifungal compounds in postharvest pear.     

Genome-wide identification and expression analysis of the lipoxygenase gene family during peach fruit ripening under different postharvest treatments

In plants, lipoxygenase (LOX), facilitated by the LOX family genes is closely related to fruit ripening and senescence, but research on LOX in peach fruit is limited. To study the roles of LOX family genes in fruit ripening during storage, a comprehensive overview of the LOX gene family in peach is presented, including their phylogenetic relationships, gene structures and subcellular localizations. Additionally, the fruit quality, including fruit firmness, ethylene production and soluble solids content under different storage conditions, were assessed. Finally, 12 peach genes that encode LOX proteins have been identified, and comparisons of the PpaLOX gene expression levels under different postharvest treatments in peach fruit suggest that PpaLOX2.1, PpaLOX7.1, PpaLOX7.2, and especially PpaLOX2.2, may be required in peach fruit ripening during storage. The results will be useful to further analyze the functions of the LOX family of genes in plants.     

Lipid-degrading enzymes from potato tubers

Three varieties of potato were used to investigate the activity of lipolytic acyl hydrolase, (LAH) and lipoxygenase, (LOX), for a short period after harvest. Both enzymes displayed very low levels of activity during the first few days, followed by an increase in later storage, with the hydrolase activity of Désirée tubers remaining low. An inverse relationship was found between the total LOX activity and the percentage of activity obtained in a particulate form. Only when the total LOX content was below 0.7 units (μmol/g/min fr. wt), was it possible to obtain a highly active particulate fraction. LAH particulate activity was dependent upon both enzymes remaining low. Protoplasts were isolated by the use of cell-degrading enzymes. When the total LOX activity in the tubers was low, 50% of this activity could be obtained in intact protoplasts. Once the LOX concentration in the tubers had risen, fewer intact protoplasts were isolated. No particulate activity of either enzyme was found when these protoplasts were lysed. The two lipid-degrading enzymes were not located in the amyloplasts.