番茄果实不同发育阶段香气成分组成及变化

以陕西杨凌地区主栽的番茄品种'金棚1号'为试验材料,通过固相微萃取和GC/MS联用技术,对番茄果实不同成熟阶段的香气成分及其组成变化进行了研究.结果表明,'金棚1号'番茄果实共检测到54种香气成分,主要成分为醛类、酸类、醇类、酮类、酯类、酚类等.在果实的不同发育阶段,香味组分及其含量差异较大.醛类物质在绿熟期相对含量较高,为45.87%,在半熟期、硬熟期、完熟期的相对含量分别为12.65%、16.62%、17.15%,其中C6醛在绿熟期占43.7%,完熟期占15.27%,为醛类物质的主要成分;酸类物质含量在4个发育时期中先上升后下降,在半熟期含量达到最高,为15.2%,在完熟期酸类物质含量下降,为6.93%;酮类物质在完熟期含量达到最大,为18.27%;在绿熟期检测到4种重要的番茄特征香气物质,半熟期检测到5种番茄特征香气物质,硬熟期和完熟期各检测到6种番茄特征香气物质.说明随着果实的成熟,特征香气物质种类增多.     

Reversible Inhibition of Tomato Fruit Gene Expression at High Temperature (Effects on Tomato Fruit Ripening)

The reversible inhibition of three ripening-related processes by high-temperature treatment (38[deg]C) was examined in tomato (Lycopersicon esculentum L. cv Daniella) fruit. Ethylene production, color development, and softening were inhibited during heating and recovered afterward, whether recovery took place at 20[deg]C or fruit were first held at chilling temperature (2[deg]C) after heating and then placed at 20[deg]C. Ethylene production and color development proceeded normally in heated fruit after 14 d of chilling, whereas the unheated fruit had delayed ethylene production and uneven color development. Levels of mRNA for 1-aminocyclopropane-1-carboxylic acid oxidase, phytoene synthase, and polygalacturonase decreased dramatically during the heat treatment but recovered afterward, whereas the mRNA for HSP17 increased during the high-temperature treatment and then decreased when fruit were removed from heat. As monitored by western blots, the HSP17 protein disappeared from fruit tissue after 3 d at 20[deg]C but remained when fruit were held at 2[deg]C. The persistence of heat-shock proteins at low temperature may be relevant to the protection against chilling injury provided by the heat treatment. Protein levels of 1-aminocyclopropane-1-carboxylic acid oxidase and polygalacturonase also did not closely follow the changes in their respective mRNAs. This implied both differences in relative stability and turnover rates of mRNA compared to protein and nontranslation of the message that accumulated in low temperature. The results suggest that high temperature inhibits ripening by inhibiting the accumulation of ripening-related mRNAs. Ripening processes that depend on continuous protein synthesis including ethylene production, lycopene accumulation, and cell-wall dissolution are thereby diminished.     

Contrasted Responses to Root Hypoxia in Tomato Fruit at Two Stages of Development

The biochemical consequences of root hypoxia have been documented in many sink organs, but not extensively in fruit. Therefore, in the present study, the response to root hypoxia in tomato fruit (Solanum lycopersicum L.) was investigated at two developmental stages, during the cell division and the cell expansion phases. Our results showed that in dividing fruit, root hypoxia caused an exhaustion of carbon reserves and proteins. However, ammonium and major amino acids (glutamine, asparagine and γ–aminobutyric acid (GABA)) significantly accumulated. In expanding fruit, root hypoxia had no effect on soluble sugar, protein and glutamine contents, whereas starch content was significantly decreased, and asparagine and GABA contents slightly increased. Metabolite contents were well correlated with activities of the corresponding metabolising enzymes. Contrary to nitrogen metabolising enzymes (glutamine synthetase, asparagine synthetase and glutamate decraboxylase), the activities of enzymes involved in sugar metabolism (invertase, sucrose synthase, sucrose phosphate synthase and ADP glucose pyrophosphorylase) were significantly reduced by root hypoxia, in diving fruit. In expanding fruit, only a slight decrease in ADP glucose pyrophosphorylase and an increase in asparagine synthetase and glutamate decarboxylase activities were observed. Taken together, the present data revealed that the effects of root hypoxia are more pronounced in the youngest fruits as it is probably controlled by the relative sink strength of the fruit and by the global disturbance in plant functioning.     

Ripening Physiology of Fruit from Transgenic Tomato (Lycopersicon esculentum) Plants with Reduced Ethylene Synthesis

The physiological effects of reduced ethylene synthesis in a transgenic tomato (Lycopersicon esculentum) line expressing 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase enzyme have been examined. Fruit from the transgenic line 5673 ripen significantly slower than control fruit when removed from the vine early in ripening. In contrast, fruit that remain attached to the plants ripen much more rapidly, exhibiting little delay relative to the control. Ethylene determinations on attached fruit revealed that there was significantly more internal ethylene in attached than detached fruit. The higher ethylene content can fully account for the observed faster on-the-vine ripening. All of the data are consistent with a catalytic role for ethylene in promoting many, although not all, aspects of fruit ripening. Biochemical analyses of transgenic fruit indicated no significant differences from controls in the levels of ACC oxidase or polygalacturonase. Because transgenic fruit are significantly firmer than controls, this last result indicates that other enzymes may have a significant role in fruit softening.     

Effect of Heat Treatment on the Development of Polygalacturonase Activity in Tomato Fruit during Ripening

When mature green tomato fruits are stored at 22?C for 30 days,they ripen normally and soften, but if they are kept at 33?Cfor 15 days (heat treatment), then stored at 22?C they do notsoften. The effect of heat treatment on the development of polygalacturonase(PG, EC 3.2.1.15 [EC] ) activities in tomato fruits during storagetherefore was studied. When mature green tomato fruits werestored at 22?C, PG activity, which had not been detectable inthe fruits, appeared as the color changed and increased dramaticallythereafter. PG activity, however, did not appear during heattreatment. When heat-treated fruits were transferred to 22?C,PG activity appeared after a 6-day lag period and increasedduring the next 30 days at 22?C to about 15% of the value detectedin ripe tomato fruits. The PG in ripe tomato fruits was composed of two isoenzymesthat had different mol wts. A high molecular form (PG-1, molwt 100K) appeared during the early stage of ripening and a lowmolecular form (PG-2, mol wt 44K) a little later. PG-2 increasedvigorously during ripening and eventually accounted for mostof the enzyme activity in the ripe fruits. Only a single isoenzyme(Y-PG, mol wt 100K), however, was detected in heat-treated tomatofruits stored at 22?C for 30 days. PG-1 and Y-PG gave the samemol wt on Sephacryl S-200 gel nitration, but could be separatedby Toyopearl HW-55 F gel filtration. (Received October 31, 1983; Accepted February 20, 1984)     

Early Application of Ethrel Extends Tomato Fruit Cell Division and Increases Fruit Size and Yield with Ripening Delay

Flowers of tomato (Lycopersicon esculentum Mill.) plants cv. Castle Rock were sprayed with 100 ppm of ethrel, 0.5 mm aminooxyacetic acid (AOA), or water (control) 2 days after anthesis. The fruit period of cell division was extended up to 16–18 days after anthesis with the application of ethrel but reduced from 10–12 days (control) down to only 6–8 days with the application of AOA. In a trend opposite to AOA application, fruits that received ethrel treatment were of higher ethylene and 1-aminocyclopropane-1-carboxylic acid (ACC) levels than control. This was noticed not only during the first 2 weeks after anthesis but also during the fruit climacteric phase. Mesocarp cells of ethrel-treated fruits were greater in number/mm² but smaller in size than control; an opposite trend was obtained with the application of AOA. This was observed for a period of 18 days after anthesis, but by that time or at earlier ages, fruits of AOA treatment were larger in size and heavier in weight than control, and both were larger and heavier than ethrel-treated ones. At 5 weeks after anthesis and thereafter, the fruit response to all treatments was totally reversed because early ethrel-treated fruits became significantly larger in size and heavier in weight with a ripening delay of about 10 and 15 days compared with those of control and AOA-treated ones, respectively. When the same treatments were applied to the whole plant, similar results were obtained because the early application of ethrel increased the fruit yield by about 15% over control with a pronounced ripening delay; an opposite trend was obtained with the application of AOA. No significant differences were found among all treatments in terms of flower or fruit abscission or fruit number/plant. The data suggest that ethylene regulates tomato fruit transmission from cell division to cell enlargement. In addition, fruit cell division is terminated only when endogenous ethylene decreases to its basal level, allowing cell enlargement to dominate and proceed as in the case of the early application of AOA. The ripening delay of ethrel-treated fruits may be caused by the longer time required for the increased cell number to reach maturation. A low level of ethrel application at the tomato early fruiting stage may be used for increasing fruit yield by increasing fruit size and consequently its quality. Received June 1, 1998; accepted December 7, 1998     

Tomato Fruit Development and Ripening Are Altered by the Silencing of LeEIN2 Gene

Loss-of-function ethylene insensitive 2 （EIN2） mutations showed ethylene insensitivity in Arabidopsis, which indicated an essential role of EIN2 in ethylene signaling. However, the function of EIN2 in fruit ripening has not been investigated. To gain a better understanding of EIN2, the temporal regulation of LeEIN2 expres- sion during tomato fruit development was analyzed. The expression of LeEIN2 was constant at different stages of fruit development, and was not regulated by ethylene. Moreover, LeEIN2-silenced tomato fruits were developed using a virus-induced gene silencing fruit system to study the role of LeEIN2 in tomato fruit ripening. Silenced fruits had a delay in fruit development and ripening, related to greatly descended expression of ethylene-related and ripening-related genes in comparison with those of control fruits. These results suggested LeEIN2 positively mediated ethylene signals during tomato development. In addition, there were fewer seeds and Iocules in the silenced fruit than those in the control fruit, like the phenotype of parthenocarpic tomato fruit. The content of auxin and the expression of auxin-regulated gene were declined in silenced fruit, which indicated that EIN2 might be important for crosstalk between ethylene and auxin hormones.     

高等植物开花结实的多胺研究进展

多胺是广泛分布于植物体内具有调控作用的生理活性物质,其代谢变化与高等植物的 生长和发育关系密切。本文概述了多胺与植物花芽形成、花器官分化以及开花、坐果和果实发育的关系;并就外源多胺对植物开花坐果的影响做了述评,对多胺在植物开花结实中可能 的作用机理及今后的研究方向和应用潜力进行了讨论。     

高等植物开花结实的多胺研究进展

多胺是广泛分布于植物体内具有调控作用的生理活性物质,其代谢变化与高等植物的生长和发育关系密切。本文概述了多胺与植物花芽形成、花器官分化以及开花、坐果和果实发育的关系;并就外源多胺对植物开花坐果的影响做了述评,对多胺在植物开花结实中可能的作用机理及今后的研究方向和应用潜力进行了讨论。     

番茄果实早期发育的分子生理机制研究进展

番茄(Solanum lycopersicum)是目前世界上种植面积最广且最受欢迎的蔬菜作物之一, 也是肉果及茄科的重要模式植物。番茄果实发育主要分为早期果实发育和果实成熟2个时期, 但果实形态结构和大小主要决定于早期果实发育时期。该文围绕番茄早期果实发育时期植物激素、细胞周期、表观遗传和源库代谢等多方面调控的分子机制进行了综述, 旨在认识植物生长与发育的基本生物学问题及促进基础理论研究成果在生产中应用。     

番茄ACC合成酶cDNA克隆及其对果实成熟的反义抑制

利用RT—PcR技术克隆了ACC合成酶多基因家族成员之－LE-ACC2编码区约1．7kb的cDNA,经酶切图谱和序列分析鉴定无误后,反向插入到植物表达载体pBin437中,构建了表达Acc合成酶反望RNA的二元载体。经农杆菌途径转化番茄“丽春”品种后,通过PCR检测从抗卡那霉素再生植株中筛选到6株转基因植株,Southern杂交确证了外源基因是以单拷贝插入到番茄染色体中;对果实乙烯释放的测定结果表明转基因番茄果实的乙烯释放量仅为对照的30％左右,在室温下转基因番茄果实采后保存60 d以上仍然没有变红、软化。以上结果表明其反义RNA在转基因番茄中的表达能有效地抑制乙烯的生物合成从而延缓果实成熟,表现出良好的耐储保鲜特性。对转基因植株子一代(T1)的分析结果进一步表明反义ACC合成酶基因以典型的单基因方式传到子代。通过对子二代的分析已初步筛选到一 个耐储藏的转基因番茄纯合品系。     

CNR转录因子在番茄果实成熟过程中的功能

SPL转录因子在植物中广泛存在并参与植物生长、发育和成熟过程,CNR是SPL转录因子家族中的一个成员,其作用机制尚不清楚.通过RNA-seq、qRT-PCR和染色质免疫共沉淀技术(ChIP)确定转录因子CNR直接作用的新的靶基因,旨在揭示番茄果实成熟过程中CNR的转录调控网络.通过RNA-seq筛选出野生型AC和突变体...     

Effect of the Calcium on Polygalacturonase (PG) Activity and Synthesis at Different Ripening Stages of Tomato Fruits

It has been reported that PG is a key enzyme related to the tomato fruit ripening and that the application of calcium can dramatically decrease the PG activity and delay the ripening of fruits. In this paper the effects of calcium treament at various ripening stages on the transformation of absorbed calcium, PG activity and PG synthesis in tomato fruits were studicd. According to the analysis of calcium by atomic absorption spectroscopy, it was shown that the soluble and total calcium contents in pericarp of fruits treated with calcium at mature-green stage were increased significantly, and that more soluble calcium was transformed into bound calcium. Both the absorption and transformation of calcium decreased in fruits treated with calcium at later stage of ripening. The inhibition of calcium on PG activity was most effective by treatment at mature-green stage, but less effective at later stage of ripening. One reason for the decrease of calcium inhibition was probably due to the decline of calcium absorption as fruit ripening. The polyacrylamide gel electrophoresis of PG showed that PG with a molecular weight of 46.7 kD was absent in mature-green fruits, and PG synthesis occurred only at the later stage of ripening. It seems that the earlier the treatment was done the more effective of the calcium inhibition of PG synthesis. Based on the above results, it was concluded that the PG plays a major role in ripening and senescence of tomato fruits, and both PG synthesis and its activity were inhibited by calcium. In order to delay the ripening and senescence of tomato fruits, the treatment with calcium should be done at mature-green stage.     

Effect of Post-Infiltration Soil Aeration at Different Growth Stages on Growth and Fruit Quality of Drip-Irrigated Potted Tomato Plants (Solanum lycopersicum)

Soil hydraulic principles suggest that post-infiltration hypoxic conditions would be induced in the plant root-zone for drip-irrigated tomato production in small pots filled with natural soil. No previous study specifically examined the response of tomato plants (Solanum lycopersicum) at different growth stages to low soil aeration under these conditions. A 2 × 6 factorial experiment was conducted to quantify effects of no post-infiltration soil aeration versus aeration during 5 different periods (namely 27–33, 34–57, 58–85, 86–99, and 27–99 days after sowing), on growth and fruit quality of potted single tomato plants that were sub-surface trickle-irrigated every 2 days at 2 levels. Soil was aerated by injecting 2.5 liters of air into each pot through the drip tubing immediately after irrigation. Results showed that post-infiltration aeration, especially during the fruit setting (34–57 DAS) and enlargement (58–85 DAS) growth stages, can positively influence the yield, root dry weight and activity, and the nutritional (soluble solids and vitamin C content), taste (titratable acidity), and market quality (shape and firmness) of the tomato fruits. Interactions between irrigation level and post-infiltration aeration on some of these fruit quality parameters indicated a need for further study on the dynamic interplay of air and water in the root zone of the plants under the conditions of this experiment.     

Effect of Sodium Chloride on Fruit Ripening of the Nonripening Tomato Mutants nor and rin

Tomato (Lycopersicon esculentum Mill) plants of the nonripening mutant nor, the ripening-inhibited mutant rin, and the normal cultivar `Rutgers' were grown in nutrient solution supplemented with 3 grams per liter NaCl from the time of anthesis. In plants treated with NaCl, all the ripening parameters of the fruits of the nor mutant increased, but those of the rin mutant did not. The ripening of the fruits of the NaCl-treated nor plants was characterized by the development of a red color and taste, increased pectolytic activity, and increased evolution of CO₂ and ethylene. These changes do not normally take place in nor under control conditions. The values of these ripening parameters in nor were lower than those of the normal Rutgers fruits. In addition, both in nor and rin and in the normal variety, exposure of the plants to NaCl shortened the developmental period of the fruit, decreased the fruit size, and increased the concentrations of total soluble solids, Na⁺, Cl⁻, reducing sugars, and titratable acids in the fruit. The role of NaCl in overcoming the inability of nor to ripen is discussed.     

Stock-Scion Interactions of Normal and Fruit Ripening Mutants rin and nor in Tomato

Scions of the non-ripening rin and nor tomato strains (Lycopersicum esculentum Mill.) were grafted on normal understock plants (cv. Rutgers) in an effort to study the influence of roots and vegetative tissue on the ripening behavior of the tomato fruit. Receiprocal grafts of ‘Rutgers’ scions on rin and nor understocks as well as grafted and ungrafted controls were also established. No alteration in the ethylene, and CO₂ evolution and color development of either mutant fruits on normal understock or of normal fruits on mutant understock occurred. We suggest that the inability of rin and nor mutant fruits to ripen normally stems either from the presence in mutant fruit of a non-translocatable ripening inhibitor, or from the absence of a non-translocatable ripening factor.     

Carboxypeptidase Activity of Tomato Fruit during the Ripening Process and Some Enzymatic Properties

Carboxypeptidase activity of tomato fruit reached a maximum at an early period of ripening. During storage of the fruit at 25°C, the enzyme activity decreased, accompanied by a fall of the pH value of the sap.

The enzyme was apparently localized in the soluble fraction, as determined by differential centrifugation.

The enzyme was optimally active at pH 5.0 ~ 5.5, was most stable at pH 4.5 ~ 6.5, and was strongly inhibited by DFP and HgCl₂, but not by EDTA and 1,10-phenanthroIine. Z-dipeptides containing arginine, proline and several neutral amino acids were hydrolyzed by the enzyme.

The similarity of the enzymatic properties of the present enzyme to those of other plant carboxypeptidases and pig kidney cathepsin A is also discussed.     

Effect of Antisense Suppression of Endopolygalacturonase Activity on Polyuronide Molecular Weight in Ripening Tomato Fruit and in Fruit Homogenates

Fruit of tomato (Lycopersicon esculentum Mill.) in which endopolygalacturonase (PG) activity had been suppressed to <1% of wild-type levels were slightly firmer than nontransgenic controls later in ripening. Enzymically inactive cell walls were prepared from these ripening fruit using Tris-buffered phenol. When extracted with chelator followed by Na2CO3, the amounts of pectin solubilized from cell walls of nontransgenic control or from transgenic antisense PG fruit were similar. Size-exclusion chromatography analysis showed that, relative to controls, in antisense PG fruit polyuronide depolymerization was delayed in the chelator-soluble fraction throughout ripening and reduced in the Na2CO3-soluble fraction at the overripe stage. Reduced pectin depolymerization rather than altered extractability thus may have contributed to enhanced fruit firmness. Substantially larger effects of suppressed PG activity were detected in tomato fruit homogenates processed to paste. In control paste the majority of the polyuronide was readily soluble in water and was very highly depolymerized. In antisense PG paste the proportion of polyuronide solubilized by water was reduced, and polyuronides retained a high degree of polymerization. The suppression of fruit PG activity thus has a small effect on polyuronide depolymerization in the fruit but a much larger effect in paste derived from these fruit. This indicates that in the cell wall PG-mediated degradation of polyuronide is normally restricted but that in tissue homogenates or in isolated cell walls this restriction is removed and extensive pectin disassembly results unless PG is inactivated.     

Salmonellae in Fish Meal Plants: Relative Amounts of Contamination at Various Stages of Processing and a Method of Control

Previous studies have shown that Menhaden fish meal, a common ingredient of animal feeds, is frequently contaminated with salmonellae. Animals that eat contaminated feed may become infected. If they, in turn, are eaten by humans, they may be a means by which salmonellae are introduced into the human population. Epidemiological studies of the fish-meal industry were carried out to determine the sources of salmonellae in fish meal and the factors affecting the persistence and survival of salmonellae during the processing of fish meal. Examination of 190 fish immediately after they came from the Gulf of Mexico revealed no salmonellae, but salmonellae were frequently isolated from samples of fish taken from the boats when they arrived at the plants. Salmonellae were also frequently isolated from dockside water at each of the plants. Approximately 50% of the samples taken in the raw fish processing areas were contaminated with salmonellae. The percentage of samples yielding salmonellae decreased progressively through the various sequences of processing, but more than 15% of the samples taken from the finished products were also positive. Salmonellae were isolated from the raw area of the plant most frequently while the plant was operating and less frequently when the plant was idle, whereas in the processing area of the plant the reverse was true. Salmonellae appeared to survive and multiply in the processing area of the plant while the plant was idle, which resulted in contamination of the first portion of each day's production. Salmonellae in the processed fish meal were reduced to nondetectable levels by reprocessing the first 45 min of each day's production.