Lycopene induction in Cucurbita moschata cotyledons by CPTA

2-(4-Chlorophenylthio) triethylamine hydrochloride (CPTA) inducedthe rapid accumulation of lycopene in Cucurbita moschata cotyledons.Concomitant with this increase, was a decrease in chlorophyllconcentration in green seedlings, a cessation of further plumuleand cotyledonary growth and an increase in cotyledon respiration.Light was required for maximum lycopene accumulation. (Received August 4, 1973; )     

Alanine aminotransferase from Cucurbita moschata cotyledons

Alanine aminotransferase increased in pumpkin cotyledons duringgermination with the greatest increase occurring in green cotyledons.The enzyme was found in the soluble fraction and was inhibitedby NH₂OH and p-chloromercuribenzoate. Pyridoxal phosphate andglutathione or dithiothreitol overcame die respective inhibition.Dialysis of the enzyme reduced enzyme activity but the activitywas restored by the addition of pyridoxal phosphate. Alanineaminotransferase was proposed to play a major role in the synthesisof the alanine which occurs in pumpkin cotyledons during germination. (Received September 17, 1975; )     

The metabolism of proline in cotyledons of pumpkin (Cucurbita moschata)

Exogenous proline-U-₁₄C is readily metabolized to glutamate,ornithine, sugars, CO₂, and organic acids, and is incorporatedinto protein by etiolated and green pumpkin cotyledons. As littletranslocation of proline from the cotyledons occur, it was proposedthat in young tissue proline is converted to glutamate, ornithineor sugar which are then readily translocated from the cotyledons.In older tissue some glutamate carbon derived from proline isalso used as an energy source and metabolized to CO₂. As proteinsynthesis is occurring rapidly in these cotyledons, considerableproline is incorporated into new protein. After 10-hr, 15% ofthe absorbed radioactivity still remained as free proline. ¹Present address: Instituto de Ciencias Biologicas, UniversidadeFederal de Vicosa, Vicosa, Minas Gerais, Brasil. (Received February 1, 1974; )     

Glutamine synthesis in germinating seeds of Cucurbita moschata

During germination, an increase in glutamine and glutamine synthetase[L-glutamate: ammonia ligase (ADP), EC 6.3.1.2 [EC] ] occurred inthe cotyledons reaching a maximum at 4 to 6 days. The enzymehad a Km of 4.5 nun for L-glutamate, and 0.67 mu for hydroxylamine.Hydroxylamine exhibited substrate inhibition kinetics. The enzymewas inhibited by calcium ion, fluoride ion and p-hydroxymercuribenzoatebut not by EDTA, sodium ion or chloride ion. The sulf hydrylinhibition was reversed by dithiothreitol. In vivo synthesisof glutamine-¹⁴C from glutamate-¹⁴C was found to parallel theincrease in glutamine content and the in vitro glutamine synthetaseactivity during germination. ¹ Present address: Department of Biology, Mercyhurst College,Erie, Pennsylvania 16501, U.S.A. (Received June 12, 1971; )     

Light and chlorophyll gradients within Cucurbita cotyledons

Abstract. Measurement of light within 10–14-d-old green and etiolated Cucurbita pepo cotyledons were made with fibre-optic microprobes to assess the influence of chlorophyll distribution and anatomical variations in mesophyll cell type (spongy versus palisade) on internal light pattern. More than 50% of the pigment in green cotyledons occurred in the upper (adaxial) 300 μm and this gradient strongly influenced the internal propagation of 680 nm light. When the upper (adaxial) surface was irradiated with 680 nm light, almost complete absorption occurred within the first 400 μm (palisade) of approximately 1200-μm-thick cotyledons. In contrast, when lower (abaxial) surfaces were irradiated with 680 nm light, penetration extended throughout the spongy mesophyll to about the 700 μm depth. Measurements of collimaled and scattered light gradients at 550, 680 and 750 nm indicated that collimaled light was rapidly scattered by mesophyll cells. In cotyledons irradiated on the upper surface, spongy mesophyll cells received only scattered light. Furthermore, comparisons of scattered light gradients obtained from cotyledons irradiated on upper and lower surfaces suggested that spongy mesophyll cells scatter light more effectively than palisade cells, probably due to the greater proportion of intercellular air spaces in spongy mesophyll tissue. These data also indicate that both the spectral quality and quantity of light incident on palisade versus spongy mesophyll cells differs, perhaps contributing to developmental and physiological differences between these two mesophyll cell types.     

Embryoid formation by fragments of cotyledons and hypocotyls in Cucurbita pepo

Summary After a prolonged culture on Murashige-Skoog medium the primary explants of hypocotyls and cotyledons of the pumpkin develop embryoid-producing callus tissue. Ten separate strains of such tissue have been obtained and have now been in culture for more than one year, continuing to produce embryoids.     

农杆菌介导南瓜遗传转化体系的建立

以南瓜金辉一号（Cucurbita moschata＇ Jinhui1＇）为实验材料,利用根癌农杆菌（Agrobacterium tumefaciens）介导转化南瓜子叶节,研究了预培养时间、侵染时间、乙酰丁香酮（AS）浓度和共培养时间,抗生素羧苄青霉素（Carb）、头孢霉素（Cef）以及筛选剂卡那霉素（Kan）等因素对离体不定芽的影响,建立了南瓜最适遗传转化体系。结果表明：外植体预培养0天,侵染时间30分钟,AS浓度为100mg·L^-1,共培养5天可获得最高遗传转化效率;最适除菌剂为Cef,其最适浓度为500mg·L^-1;最适Kan筛选浓度为100mg·L^-1;在MS培养基上培养抗性芽生根,经PCR和Southern blot检测,证明为转基因植株。     

农杆菌介导南瓜遗传转化体系的建立

以南瓜金辉一号(Cucurbita moschata ‘Jinhui 1’)为实验材料, 利用根癌农杆菌(Agrobacterium tumefaciens)介导转化南瓜子叶节, 研究了预培养时间、侵染时间、乙酰丁香酮(AS)浓度和共培养时间, 抗生素羧苄青霉素(Carb)、头孢霉素(Cef)以及筛选剂卡那霉素(Kan)等因素对离体不定芽的影响, 建立了南瓜最适遗传转化体系。结果表明: 外植体预培养0天,侵染时间30分钟, AS浓度为100 mg·L^–1, 共培养5天可获得最高遗传转化效率; 最适除菌剂为Cef, 其最适浓度为500mg·L^–1; 最适Kan筛选浓度为100 mg·L^–1; 在MS培养基上培养抗性芽生根, 经PCR和Southern blot检测, 证明为转基因植株。     

Phosphoenolpyruvate carboxykinase and gluconeogenesis in cotyledons of Cucurbita pepo

1. The aim of this work was to investigate the role of phosphoenolpyruvate carboxykinase (ATP:oxaloacetate carboxy-lyase (transphosphorylating) EC 4.1.1.49) in the conversion of fat to sugar by the cotyledons of seedlings of Cucurbita pepo. 2. The enzyme was partially purified from the cotyledons of 5-day-old seedlings. The Michaelis constants for oxaloacetate and ATP were 56 and 119 micron, respectively. The decarboxylation reaction was optimum at pH 7.4. A range of intermediary metabolites did not affect the activity of the enzyme, but 3-mercaptopicolinic acid at micron concentrations was an effective inhibitor. 3. Centrifugation of extracts of 5-day-old cotyledons sedimented appreciable proportions of the ribuloseibisphosphate carboxylase, isocitrate lyase and fumarate hydratase present but very little of the phosphoenolpyruvate carboxykinase. 4. Measurements of phosphoenolpyruvate carboxykinase of cotyledons during germination showed that the maximum catalytic activity exceeded, and changed coincidently with, the rate of gluconeogenesis. 5. 3-Mercaptopicolinic acid inhibited gluconeogenesis from [1-14C]- and [2-14C]acetate supplied to excised cotyledons. The detailed distribution of 14C indicated inhibition of the conversion of oxaloacetate to phosphoenolpyruvate. 6. It is concluded that in marrow cotyledons phosphoenolpyruvate carboxykinase is in the soluble phase of the cytoplasm and catalyses a component reaction of gluconeogenesis.     

南瓜两性花的形态与结构研究

对南瓜的两性花进行外部形态及结构的研究,结果表明：南瓜的两性花可有子房上位花、子房半下位花和子房下位花三种类型：花萼、花冠均为５,合瓣;雄蕊３,其中有两枚各由两个雄蕊合生而成,分离和部分联合,花药结构特殊,花粉发育正常;雌蕊具有单个或两个柱头及花柱。子房壁结构正常。上方的子房壁表皮发育完好,具气孔器。胚珠在外形上也发育正常。两性花与单性花同生长在一个植株上,可以连续多代稳定地遗传,萌生当代植株的种子来源于上一代雌花。这对探讨被子植物的系统进化关系有着重要的意义     

Metabolic alterations in cotyledons of Cucurbita pepo infected by cucumber mosaic virus

Changes in the capacities of enzymes in various metabolic pathwayshave been measured during infection of cotyledons of Cucurbitapepo L. with cucumber mosaic virus (CMV). Starch accumulationand low sucrose content, which are characteristic of the earlystages of infection, are reversed in the later stages of infection.The decline in starch correlated with a reduced capacity forstarch synthesis (ADP-glucose pyrophosphorylase) and a risein the capacity for starch degradation (total starch hydrolase,starch phosphorylase). ¹⁴CO₂ feeding experiments, conductedat saturating CO₂ concentration, show that the newly-assimilatedcarbon was lost at a lower rate from infected cotyledons andless was incorporated into structural carbohydrates, phosphorylatedintermediates plus organic acids, more into soluble sugars,amino acids and proteins. At a later stage of infection therewere dramatic increases in respiratory capacity and a substantialalteration of carbohydrate metabolism. The infection had a largestimulatory effect on the capacity for oxidative pentose-phosphatepathway (glucose-6-phosphate dehydrogenase, 6-phospho-gluconatedehydrogenase), glycolysis (ATP- and pyrophosphate-dependentphosphofructokinases), tri-carboxylic acid cycle (isocitratedehydrogenase, fumarate hydratase), anaplerotic reactions (NAD-dependentmalic enzyme, phosphoenolpyruvate car-boxylase) and oxidativeelectron transport (cytochrome c oxidase). While there wereno overall changes in photosynthetic rate (measured in saturatingCO₂), infection either reduced (Rubisco and glycerate kinase)or did not affect (chloroplastic fructose bis-phosphatase andhydroxypyruvate kinase) the capacities of the photosyntheticcarbon reduction pathway or the photosynthetic carbon oxidationpathway. Key words: Plant-virus interaction, sucrose, starch, enzymes, ¹⁴CO₂ incorporation, O₂ flux     

Protein composition of Cucurbita maxima and C. moschata seeds

Seeds of Cucurbita maxima, C. moschata and their interspecific hybrids were used to evaluate the intrapopulational and interpopulational variation of their protein composition. Three immunoprecipitating systems common to all the studied samples were detected by the Ouchterlony technique. Fourteen protein bands were identified by polyacrylamide gel electrophoresis (PAGE) whereas 23 bands were identified by sodiumdodecylsulfate (SDS)-PAGE. Using Western blotting (WB) also 23 bands were detected. The Jaccard's index of similarity calculated from SDS-PAGE and WB varied between 91 and 100 % for all the compared pairs of samples. These results demonstrate a high uniformity in the protein composition of all the samples and do not allow for their clear characterization.     

Grafting onto Cucurbita moschata rootstock alleviates salt stress in cucumber plants by delaying photoinhibition

To determine how the use of a given rootstock can influence the functioning of the photosynthetic apparatus of the scion under salt stress, the growth, gas exchange, photosystem II (PSII) efficiency, xanthophyll cycle, and chloroplast ultrastructure of nongrafted, self-grafted, and pumpkin-grafted (hereafter referred to as rootstock-grafted) cucumber (Cucumis sativus L.) plants were investigated at day 15 after being treated with 90 mM NaCl. The reductions in plant growth of the rootstock-grafted plants were lower than those of the nongrafted and self-grafted plants under 90 mM NaCl. The net photosynthetic rate, stomatal conductance, maximal and effective quantum yield of PSII photochemistry, photochemical quenching coefficient, and effective quantum-use efficiency of PSII in the light-adapted state of the nongrafted and self-grafted plants were significantly decreased under 90 mM NaCl. However, these reductions were alleviated when the cucumber plants were grafted onto the pumpkin (Cucurbita moschata Duch.) rootstock. The intercellular CO₂ concentrations were significantly increased in the nongrafted and self-grafted plants under 90 mM NaCl, whereas it was decreased in the rootstock-grafted plants. Nonphotochemical quenching (NPQ) and the deepoxidation state of the xanthophyll cycle were significantly increased under 90 mM NaCl, particularly in the rootstockgrafted plants, suggesting the rootstock-grafted plants had higher potential to dissipate excess excitation energy and reduce the probability of photodamage to PSII. Under 90 mM NaCl, the number of grana was reduced, the thylakoids were swollen, and starch granules accumulated in all plants. However, the damage of chloroplast ultrastructure was alleviated in the rootstock-grafted plants. Taken together, the use of C. moschata rootstock alleviated salt stress in cucumber plants by delaying photoinhibition, probably due to a lower incidence of both stomatal and nonstomatal factors limiting photosynthesis.     

南瓜高效再生体系的建立

南瓜(Cucurbita moschata)再生率较低, 为建立高效的南瓜再生体系, 以南瓜子叶为外植体, 进行35组不同激素浓度的不定芽诱导研究。结果表明, 南瓜再生受培养基中激素浓度和配比的影响, 适宜浓度6-苄氨基腺嘌呤(6-BA)能有效促进不定芽形成; 单独使用脱落酸(ABA)诱导使南瓜子叶发黄, 但与6-BA组合使用可显著提高外植体的再生能力, 1.0 mg?L ^-16-BA与0.5 mg?L ^-1ABA组合南瓜芽再生率高达90.26%。将不定芽置于MS培养基中进行生根培养, 再生苗移栽易成活。从子叶接种到苗再生约需70天。     

南瓜高效再生体系的建立

南瓜(Cucurbita moschata)再生率较低, 为建立高效的南瓜再生体系, 以南瓜子叶为外植体, 进行35组不同激素浓度的不定芽诱导研究。结果表明, 南瓜再生受培养基中激素浓度和配比的影响, 适宜浓度6-苄氨基腺嘌呤(6-BA)能有效促进不定芽形成; 单独使用脱落酸(ABA)诱导使南瓜子叶发黄, 但与6-BA组合使用可显著提高外植体的再生能力, 1.0 mg∙L ^-16-BA与0.5 mg∙L ^-1ABA组合南瓜芽再生率高达90.26%。将不定芽置于MS培养基中进行生根培养, 再生苗移栽易成活。从子叶接种到苗再生约需70天。     

Multiple forms of phytase in germinating cotyledons of Cucurbita maxima

Multiple forms of phytase (myoinositol hexaphosphate phosphohydrolase, EC 3.1.3.8) have been isolated in highly purified forms from germinating Cucurbita maxima cotyledons using acetone and ammonium sulphate fractionation, Sephadex gel filtration and ion exchange chromatography on DEAE- and CM-cellulose. Gel filtration produced two peaks of phytase activity; phytase I (high MW) and phytase II (low MW). Phytase I was further resolved into 4 distinct species on CM-cellulose and these were designated phytase IA, IB, IC and ID, according to their elution order. On the other hand, phytase II remained as a single species with a purification of 35-fold. The MWs of each phytase I species were identical (MW 66 500 ± 4000) and they were twice the MW of phytase II (MW 32 400 ± 4000) indicating that I and II may be structurally related. The properties of various molecular forms were compared. The difference in properties between phytase II and phytase I isoenzymes (IA, IB, IC and ID) was more pronounced than that observed among the isoenzymes of phytase I alone.     

Carotenoid synthesis in Turkish lemons and oranges as influenced by triethylamine derivatives

Two triethylamines, 2-(4-chloro-phenylthio)-triethylamine (CPTA) and 4-chloro[β-(diethylamino)-ethyl]-benzoate (CDEB), were used to investigate C₃₀ carotenoid biosynthesis in Turkish oranges and lemons. It was not possible to determine the pathway, since not all the intermediates from phytoene to the C₃₀ compounds were observed. Lycopene and ζ-carotene, absent in controls, were identified in large amounts in certain CPTA- and CDEB- treated lemons and oranges. Furthermore there were varietal differences, since CDEB-treated Turkish oranges did not produce the increases in α- and β-carotene earlier observed in Californian Citrus fruits.     

Alpha-amylase synthesis in wheat kernels as influenced by the seed coat

The effect of seed coat removal on the synthesis of α-amylase isoenzymes in wheat was investigated. The immature wheat endosperm-aleurone (seed coat and embryo detached) produced considerably less α-amylase activity than immature whole or de-embryonated wheat kernels, when incubated under identical conditions of 18.5 C and 99% humidity, in the presence or absence of gibberellic acid (GA₃). The incubated endosperm-aleurone also exhibited unique α-amylase isoenzyme composition when compared to the isoenzyme compositions of incubated whole and de-embryonated immature and mature wheat kernels both in the presence or absence of GA₃. Subsequent studies indicated that the seed coat may contain factor(s) required for normal α-amylase isoenzyme synthesis.     

Location of gluconeogenesis from phosphoenolpyruvate in cotyledons of Cucurbita pepo.

1. The aim of this work was to discover the location of the enzymes that convert phosphoenolpyruvate to fructose 6-phosphate during gluconeogenesis in fatty seeds. Cotyledons of 5-day-old dark-grown seedlings of marrow (Cucurbita pepo) were used as experimental material. 2. Cotyledons were separated into palisade and mesophyll tissue. Extracts of the two tissues had comparable activities of gluconeogenic enzymes. 3. Extracts of cotyledons were fractionated by density gradient centrifugation to yeild mitochondria and glyoxysomes, and by gel filtration to yield proplastids. The isolated organelles retained their characteristic ultrastructure and appreciable amounts of marker enzymes. The proportions of the total activities of phosphoglyceromutase and fructose-1, 6-diphosphatase recovered in the mitochondrial and glyoxysomal preparations were insignificant. The same was true for the activities of phosphoglyceromutase and phosphopyruvate hydratase found in the proplastid preparations. 4. Extracts of a number of other gluconeigenic plant tissues were centrifuged at 2500 times g to yield particulate preparations. None of these preparations contained a significant proportion of the total activity of phosphoglyceromutase. 5. It is suggested that gluconeogenesis from phosphoenolpyruvate in plants occurs in the cytoplasm.