Partial purification of tomato fruit peroxidase and its effect on the mechanical properties of tomato fruit skin

Peroxidase (EC 1.11.1.7)-mediated stiffening of cell walls within the fruit skin of tomato is hypothesized to regulate fruit growth. However, to date, there is no experimental evidence demonstrating that peroxidase affects the mechanical properties of skin tissue. Here, the mechanical properties of skin strips excised from a range of fruits at different ages were determined using an 'Instron' universal material testing instrument. The stiffness of tomato fruit skin strips increases 3-fold with increasing fruit age. Application of partially-purified peroxidase from the cell walls of mature tomato fruit skin significantly increased the stiffness of fruit skin irrespective of the age of fruit. Furthermore, the application of hydrogen peroxide significantly increased the stiffness of skin strips excised from fruit of an age when endogenous peroxidase isozymes associated with the termination of growth are first detected. The results support the hypothesis that the tomato fruit skin plays an integral role in the regulation of tomato fruit growth, and that changes in its mechanical properties may be mediated by peroxidase. As far as is known, this is the first demonstration that peroxidases alter the mechanical properties of the plant cell wall.     

摘心时期和留蔓数对甜瓜苗期叶面积扩展和功能叶寿命的影响

以2个厚皮甜瓜和1个薄皮甜瓜品种为材料,研究了摘心时期和留蔓数对苗期叶面积扩展和功能叶寿命的影响.结果表明,厚皮甜瓜苗期叶面积发育快于薄皮甜瓜,早熟厚皮甜瓜品种的叶面积发育快于中晚熟品种;甜瓜真叶净光合速率显著大于子叶,厚皮甜瓜的子叶光合速率高于薄皮甜瓜;摘心时预留子蔓数越多,甜瓜幼苗期叶面积扩展速度越快,但留蔓数增加会促进主蔓叶片衰老.从叶面积扩展速度和叶片功能寿命看,五叶期是甜瓜幼苗主蔓摘心的最佳时期,适宜留蔓数则因品种而异.     

Peroxidase isozyme patterns in the skin of maturing tomato fruit

The cessation of tomato fruit growth is thought to be induced by an increase in the activity of enzymes which rigidify cell walls in the fruit skin. Peroxidase could catalyse such wall‐stiffening reactions, and marked rises in peroxidase activity were recently reported in skin cell walls towards fruit maturity. Peroxidase isoforms in the fruit are here analysed using native gel electrophoresis. New isoforms of apparent M_r 44, 48 and 53 kDa are shown to appear in cell walls of the fruit skin at around the time of cessation of growth. It is inferred that these isozymes are present in the cell wall in vivo. Fruit from a range of non‐ripening mutants were also examined. Some of these do not soften or ripen for many weeks after achieving their final size. The new isozymes were found in skin cell walls of mature fruit in each of these mutants, as in the wild‐type and commercial varieties. It is concluded that the late‐appearing isozymes are not associated with fruit ripening or softening, and are probably not ethylene‐induced. They may act to control fruit growth by cross‐linking wall polymers within the fruit skin, thus mechanically stiffening the walls and terminating growth.     

Analysis of Light Transport Features in Stone Fruits Using Monte Carlo Simulation

The propagation of light in stone fruit tissue was modeled using the Monte Carlo (MC) method. Peaches were used as the representative model of stone fruits. The effects of the fruit core and the skin on light transport features in the peaches were assessed. It is suggested that the skin, flesh and core should be separately considered with different parameters to accurately simulate light propagation in intact stone fruit. The detection efficiency was evaluated by the percentage of effective photons and the detection sensitivity of the flesh tissue. The fruit skin decreases the detection efficiency, especially in the region close to the incident point. The choices of the source-detector distance, detection angle and source intensity were discussed. Accurate MC simulations may result in better insight into light propagation in stone fruit and aid in achieving the optimal fruit quality inspection without extensive experimental measurements.     

不同颜色果袋对‘云红梨2号’果皮色泽形成的影响

研究了不同颜色果袋对‘云红梨2号’果实着色的影响,比较了不同套袋处理下果皮外观着色、叶绿素、类黄酮、总酚、花色素苷含量以及花色素苷合成相关酶活性的差异.结果表明: 发育期的黑暗处理有利于解袋后梨果皮着色;不同套袋处理中,采前解袋自然光照射下梨果皮中花色素苷含量最高,着色最好,白色纸袋次之.不同套袋处理显著影响果皮中叶绿素、类黄酮、总酚和花色素苷含量,从而影响梨果皮的外观色泽.不同套袋处理的花色素苷合成酶活性差异显著;相关性分析表明,果皮中花色素苷含量与二氢黄酮醇-4-还原酶(DFR)和类黄酮3-O-葡萄糖基转移酶(UFGT)活性呈显著正相关,而与苯丙氨酸解氨酶(PAL)活性相关性不显著.     

柠檬术后止呕作用的临床研究

目的观察柠檬果临床止呕的疗效。方法随机抽取术后伴呕吐患者180例,分为3组,每组60例,男女各半。对照组肌注胃复安,柠檬皮组使用柠檬果皮划痕榨汁嗅闻,柠檬汁组口含柠檬汁或浸泡柠檬丝口服。观察3组止呕的最佳时间和作用程度。结果3种方法比较,以柠檬果皮划痕榨汁嗅闻达到止呕的效果最好。结论柠檬果皮划痕榨汁嗅闻可以在大手术后呕吐患者中使用,其方法简单,无副作用,值得推广应用。     

Subcellular localization of peroxidase in tomato fruit skin and the possible implications for the regulation of fruit growth

The cessation of tomato fruit growth has been associated with the appearance of three 'wall-bound' peroxidase isozymes in the skin of tomato fruit. However, the presence of these isozymes in the ionically eluted 'wall-bound' fraction may be an artefact of either non-specific binding of symplastic peroxidase to the cell wall, or isozymes bound to membranes included in the 'wall-bound' fraction. Therefore, subcellular localization of peroxidase in both immature and mature tomato fruit skins was studied. Immature fruits showed intense peroxidase activity associated with the tonoplast and pro-vacuolar membranes, but little or no activity associated with the cell wall. However, the presence of peroxidase activity within the cell wall of mature green fruits was confirmed. Furthermore, peroxidase activity was also observed associated with the plasma membrane and large vesicles allied to the plasma membrane. While cross-linking in cell wall components was previously assumed to be the mechanism by which peroxidase might control fruit growth, the incorporation of 'lignin-like' phenolics may also play a part. Isoelectric focusing (IEF) of both symplastic and apoplastic peroxidase extracted from immature and mature tomato fruit skin showed that all peroxidase isozymes present were highly anionic. In this current study, histochemical techniques are used to demonstrate a developmental increase in 'lignin-like' phenolics within the sub-cuticular cell walls of the fruit skin. The localization of peroxidase within tomato fruit skin is discussed in relation to its potential role in the regulation of tomato fruit growth.     

Differential Expression of Proteins in Red Pear Following Fruit Bagging Treatment

Fruit bagging is a very effective method for study of fruit qualities and anthocyanin synthesis. The characterization of differentially expressed proteins that were isolated from both bagged and normal fruit skin tissue is apparently an essential parameter for understanding the effect of shading on fruit qualities and to understand the mechanism of fruit coloring in Pyrus communis. Proteome maps of both bagged and normal P. communis 'Placer' fruit skin were obtained by performing two-dimensional electrophoresis analysis and compared to assess the extent to which protein distribution differed in pear skin. The comparative analysis showed 38 differentially expressed proteins between the two samples: with three protein spots up-regulated and 35 down-regulated in the bagged fruit. Differentially expressed protein spots were subjected to matrix-assisted laser desorption ionization time of flight (MALDI-TOF) analysis and the data compared to that of known proteins to deduce their possible functions. Of these, 21 protein spots were identified and classified into functional classes. These identified proteins were mainly involved in photosynthesis, signal transduction, energy pathway, protein folding and assembly, and carbohydrate and acidity metabolisms, and were under-expressed in bagged fruit skins. This work provides a first characterization of the proteome changes in response to fruit bagging treatment in red pears.     

制干枣品种品质性状的因子分析与综合评价

综合评价制干枣主要栽培品种的品质,为制干枣品种选择和生产利用提供科学依据。应用SPSS统计分析软件,采用因子分析对13个制干枣品种的品质性状进行了比较和排序。结果表明：（1）在13个制干枣品种中,制干率和干枣含糖量差别较小,而单果质量、果实整齐度、果皮韧性和汁液差异相对较大;各品质因子间既相互独立又存在着不同程度的相关。（2）在9个品质性状指标中,单果质量、制干率、干枣口感、干枣含糖量和果皮韧性等5个指标起决定作用。（3）因子分析结果表明,制干品质综合性状优良的品种是相枣和板枣,临汾团枣、洪赵小枣和中阳木枣相对较差,其它品种居中,这一结果与感官评价的结果基本一致。本研究表明：应用因子分析可以较好地用于制干枣品种品质性状的综合评价。     

A procedure for quantifying adhesion of conidia of Botrytis cinerea to the skin of apple fruit

Ultrasonication was evaluated as a nonchemical means to quantitatively remove conidia of Botrytis cinerea from the skin of Golden Delicious apple (Malus domestica Borkh.) fruit. A probe immersed in a suspension of conidia and generating 20 kHz at 150 W for 30- or 60-s pulses destroyed 13.3% or 29% of conidia, respectively. Destruction at 150 W for 10 s or at 30-120 W for up to 60 s was <2%. The procedure for quantifying adhesion of conidia to the skin of fruit consisted of pipetting a 50-microL water droplet containing 5 x 10(4) conidia onto the skinside of a slice of fruit, incubating the slices inside sealed 500 cm3 glass jars, excising a 1 cm diameter piece of skin bearing the droplet, and sonicating the skin in 8 mL of ice-cold water at 150 W for 10 s. The skin was removed, the suspension was centrifuged at 1250 x g for 15 min, and the supernatant was reduced to 1 mL by vacuum suction using a pipet. Conidia were stained with crystal violet and counted in a hemacytometer. Adhesion of conidia to skin was 3.0%, 14.6%, 20.8%, 39.4%, 57.6%, and 73.1% after 0, 2, 4, 8, 12, and 24 h incubation, respectively. Sonication was more effective than two other procedures for recovery of conidia. Conidia on the skin of fruit exposed to 4 microL of butyl acetate in the headspace of glass jars for 4 h at 23 degrees C increased the adhesion of conidia 107% above that for unexposed conidia. Sonication with a programmable power- and time-controlled probe was a simple, rapid, safe, and effective method for quantifying adhesion of B. cinerea conidia to the skin of apple fruit.     

红富士苹果品质与生态气象因子关系的研究

通过对我国不同生态类型区红富士苹果果实品质的调查和实验室分析,应用多元统计分析,研究了不同生态类型区红富士果实品质差异及影响果实品质的主要气象因子．红富士苹果在我国陕西渭北、甘肃陇东和山东渤海湾地区呈现出果实大、果面光洁、果色鲜艳的特征;而在西南高地果色暗红;黄河故道地区果面粗糙、着色差、果肉松;宁夏地区果实偏小．经典范相关分析筛选出影响苹果品质因素的主要气象因子,不同品质因素受气象因子的影响各异,果实花青素含量主要受年总降雨量、１０月平均温度、７月平均最高气温、９月平均最低气温、９月日照时数等气象因子的影响     

Germination and adhesion of fungal conidia on polycarbonate membranes and on apple fruit exposed to mycoactive acetate esters

The adhesion and germination of conidia of nine fungal species were assessed on polycarbonate membranes or on the skin of apple fruit in sealed glass bottles injected or not injected with acetate esters. Adhesion was determined after dislodging conidia from surfaces using a sonication probe. Adhesion and germination of conidia of Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, Penicillium citrinum, Penicillium claviforme, or Trichoderma sp. on membranes after 48 h were not increased in a 1.84 microg mL(-1) headspace of butyl acetate (BA), ethyl acetate, hexyl acetate, 2-methylbutyl acetate, pentyl acetate, or propyl acetate. Adhesion and germination of Botrytis cinerea, Penicillium expansum, and Penicillium roquefortii conidia were stimulated by all esters. Only conidia of B. cinerea and P. expansum exhibited increased adhesion and germination on the skin of apple fruit in bottles exposed to 0.92 microg mL(-1) of BA. Only conidia of B. cinerea and P. expansum produced decay in inoculated puncture wounds on fruit. Freshly made puncture wounds or 24-h-old puncture wounds in fruit were more adhesive than the unpunctured skin of fruit to conidia of B. cinerea or P. expansum. Fresh wounds were more adhesive to both fungi than 24-h-old puncture wounds. The skin and wounds of fruit were as adhesive to B. cinerea conidia as they were to P. expansum conidia. A 4-h exposure to 1.43 microg mL(-1) of BA increased adhesion of B. cinerea and P. expansum conidia in 24-h-old wounds. Results suggest that acetate-ester stimulation most likely is not a rare phenomenon in the fungi. For nutrient-dependent decay pathogens of apple fruit, acetate esters may be an alternative chemical cue used to maintain adhesion of conidia to wound surfaces.     

Surface moisture increases microcracking and water vapour permeance of apple fruit skin

• Surface moisture induces microcracking in the cuticle of fruit skins. Our objective was to study the effects of surface moisture on cuticular microcracking, the permeance to water vapour and russeting in developing ‘Pinova’ apple fruit.
• Surface moisture was applied by fixing to the fruit a plastic tube containing deionized water. Microcracking was quantified by fluorescence microscopy and image analysis following infiltration with acridine orange. Water vapour permeance was determined gravimetrically using skin segments (ES) mounted in diffusion cells.
• Cumulative water loss through the ES increased linearly with time. Throughout development, surface moisture significantly increased skin permeance. The effect was largest during early development and decreased towards maturity. Recovery time courses revealed that following moisture treatment of young fruit for 12 days, skin permeance continued to increase until about 14 days after terminating the moisture treatment. Thereafter, skin permeance decreased over the next 28 days, then approaching the control level. This behaviour indicates gradual healing of the impaired cuticular barrier. Nevertheless, permeance still remained significantly higher compared with the untreated control. Similar patterns of permeance change were observed following moisture treatments at later stages of development. The early moisture treatment beginning at 23 DAFB resulted in russeting of the exposed surfaces. There was no russet in control fruit without a tube or in control fruit with a tube mounted for 12 days without water.
• The data demonstrate that surface moisture increases microcracking and water vapour permeance. This may lead to the formation of a periderm and, hence, a russeted fruit surface.

     

国外甜瓜种质资源形态性状遗传多样性分析

对250份国外甜瓜(Cucumis melo)种质资源的19个形态性状多样性进行研究。结果表明, 国外甜瓜种质资源具有丰富的形态多样性, 平均遗传多样性指数为1.378。9个质量性状(果实形状、果皮底色、覆纹颜色、覆纹形状、网纹密度、网纹粗度、果肉颜色、果肉质地和种子颜色)和4个数量性状(单果鲜重、果肉厚度、可溶性固形物含量和种子千粒重)变异明显, 其Shannon’s指数分别大于1.0和1.9。不同生态区间种质资源遗传多样性差异明显, 多样性指数由高到低依次为: 南亚(1.512)、东北欧(1.404)、西欧(1.372)、北美(1.340)和东亚(1.281)。通过聚类分析将所有甜瓜种质划分为四大组群, 即南亚组群、东北欧组群、西欧北美组群和东亚北美组群。以印度为代表的南亚甜瓜种质形态多样性水平较高, 支持了印度次生大陆为甜瓜起源中心的观点。     

Effect of phenolic compounds in Lycopersicon esculeutum on the synthesis of ethylene

Caffeic, coumaric, sinapic and ferulic acids and naringenin were found in green tomato fruit, Chlorogenic acid accounted for 75% of the total phenolics in mature green fruit but only 35% in ripe fruit. There was very little change in the phenolic composition of the flesh of the fruit during ripening, whereas in the skin, naringenin increased markedly at the onset of the climacteric and three unidentified compounds increased during the climacteric rise. The increase in the concentration of naringenin was accompanied by an increase in the production of ethylene in the skin. Investigation of three systems producing ethylene from 4-methylmercapto-2-oxobutyric acid in the presence of peroxidase, showed that only p`-coumaric acid or naringenin were capable of acting as phenolic substrates, the other phenolic compounds being inhibitory.     

The making of a pest: the evolution of a fruit-penetrating ovipositor in Drosophila suzukii and related species

Evolutionary innovation can allow a species access to a new ecological niche, potentially reducing competition with closely related species. While the vast majority of Drosophila flies feed on rotting fruit and other decaying matter, and are harmless to human activity, Drosophila suzukii, which has a morphologically modified ovipositor, is capable of colonizing live fruit that is still in the process of ripening, causing massive agricultural damage. Here, we conducted the first comparative analysis of this species and its close relatives, analysing both ovipositor structure and fruit susceptibility. We found that the ovipositor of the species most closely related to D. suzukii, Drosophila subpulchrella, has a similar number of enlarged, evolutionarily derived bristles, but a notably different overall shape. Like D. suzukii, D. subpulchrella flies are capable of puncturing the skin of raspberries and cherries, but we found no evidence that they could penetrate the thicker skin of two varieties of grapes. More distantly related species, one of which has previously been mistaken for D. suzukii, have blunt ovipositors with small bristles. While they did not penetrate fruit skin in any of the assays, they readily colonized fruit interiors where the skin was broken. Our results suggest that considering evolutionary context may be beneficial to the management of invasive species.     

Physiological responses of mangoes cv. Kensington Pride to gamma irradiation treatment as affected by fruit maturity and ripeness

An investigation was undertaken to examine responses of mangoes cv. Kensington Pride to irradiation treatment.
Gamma irradiation of preclimacteric fruit increased fruit respiration immediately after treatment, delayed the time to attain the climacteric respiratory peak and reduced the magnitude of this peak rate. Fruit softening was unaffected whereas skin colour development was strongly inhibited by irradiation treatment. Inhibition of skin degreening was half-maximal at a dose of 200 Gy. Exposure to ethylene failed to reverse this inhibition. Less mature fruit were more strongly affected by irradiation treatment. Fruit which were partially ripe and in their climacteric rise at time of treatment were largely unaffected by irradiation. These results are discussed in terms of the utility of irradiation technology for commercial disinfestation.     

果实开裂研究进展

裂果是果实中普遍发生的一种生理性病害,如番茄、甜樱桃、苹果、枣、石榴、荔枝等均易开裂,这会造成巨大的经济损失和农业资源浪费。裂果是由多种因素综合导致,内因主要为遗传和果实的自身特性,如果实大小、形状、生长速度、含水量、果皮特性、果实开裂相关基因表达情况等;外因主要为生长环境条件,如温度、光照、降水等,以及栽培管理方式,如灌溉、防晒、矿物质和生长调节剂的施用等。文中从以上方面对果实开裂的研究进展进行综述,以期为裂果机理的进一步研究和裂果的防控提供参考。