Changes in Compositional Properties during Fruit Development and On-Tree Ripening of Two Common Apricot (Prunus armeniaca L.) Cultivars

The objective of the present study was to investigate the variations in some major primary (sugars and organic acids) and secondary (phenolics, β-carotene) metabolite contents during fruit development and ripening in two important apricot cultivars (Hacıhaliloğlu and Kabaaşı). The changes in the compositional properties of two apricot cultivars were monitored during fruit development with one-week intervals from 56 to 119 days after blossom. During fruit development, the contents of organic acids and phenolics decreased whereas that of sucrose and sorbitol increased. p-Coumaric acid was the only phenolic compound which increased in concentration during fruit development regardless of the cultivar. The content of the other phenolic compounds decreased in a cultivar-dependent manner. The β-carotene content of the cultivars showed distinct patterns of change such that 3 fold increase in β-carotene content of Kabaaşı cultivar was observed whereas the β-carotene content of the Hacıhaliloğlu cultivar did not show any significant change during fruit development.     

香蕉果实成熟软化过程中细胞壁物质的变化

系统研究了香蕉果实软化过程中细胞壁物质―醇不溶性固形物(AIS)以及3种不同性质的果胶物质:水溶性果胶(WSP)、酸溶性果胶(HP)和碱溶性果胶(OHP)含量的变化。结果表明:随果实的成熟软化,AIS的含量不断降低,且在呼吸跃变时急剧降低;WSP的含量不断增加,HP和OHP的含量不断减少,且均表现出在早期变化量少,在果实硬度迅速降低时变化明显。该研究进一步证明细胞壁物质的变化是导致香蕉果实软化的主要原因。     

Postharvest Variation in Cell Wall-Degrading Enzymes of Papaya (Carica papaya L.) during Fruit Ripening

Pectin methylesterase (PME), polygalacturonase (PG), xylanase, cellulase, and proteinase activity were determined and related to respiration, ethylene evolution, and changes in skin color of papaya (Carica papaya L.) fruit from harvest through to the start of fruit breakdown. PME gradually increased from the start of the climacteric rise reaching a peak 2 days after the respiratory peak. PG and xylanase were not detectable in the preclimacteric stage but increased during the climacteric: during the post climacteric stage, the PG declined to a level one-quarter of peak activity with xylanase activity returning to zero. Cellulase activity gradually increased 3-fold after harvest to peak at the same time as PME, 2 days after the edible stage. Proteinase declined throughout the climacteric and postclimacteric phases. A close relationship exists between PG and xylanase and the rise in respiration, ethylene evolution, and softening. Cultivar differences in postclimacteric levels of enzymic activity were not detected.

An inhibitor of cellulase activity was detected in preclimacteric fruit. The inhibitor was not benzyl isothiocyanate (BITC). BITC did inhibit PG activity, though no inhibitor of PG activity was detected in preclimacteric homogenates when BITC was highest. The results indicate that inhibitors did not play a direct role in controlling wall softening.

     

壳聚糖提高香蕉幼苗抗冷性的效应

壳聚糖(CS)预处理可降低低温胁迫下香蕉幼苗叶细胞膜脂过氧化水平和膜透性增加的程度以及超氧化物歧化酶(SOD)、过氧化物酶(POD)活性的下降幅度,提高过氧化氢酶(CAT)的活性;0.3%的壳聚糖的保护效果最好.     

Permeability Characteristics and Amino Acid Incorporation during Senescence (Ripening) of Banana Tissue

Changes in free space of banana tissue during ripening were measured using radioisotopes. Free space increased significantly about 44 hours before the onset of, and rose exponentially during the respiratory climacteric. The increase in free space indicates a progressive increase in the proportion of cells which becomes completely permeable to solutes in the ambient solution by simple diffusion. At the respiratory peak the tissue was essentially 100% free space to mannitol, sucrose, fructose and chloride.

The capacity for active uptake of solutes declined about one day before the onset of the respiratory rise and fell to a very low level by the respiratory peak.

There was no change in the level of protein or amino acids during ripening. Assays of tissue sections before and after washing indicated an increased rate of leakage of amino acids during ripening.

Studies of incorporation of 3 concentrations of ¹⁴C-labeled leucine and phenylalanine indicated marked changes in the size and specific activity of the amino acid pool at the site of protein synthesis just prior to and during the climacteric rise, due to a diffusive mixing of the labeled substrate with the previously sequestered endogenous, unlabeled pool of substrate. The use of a high concentration of exogenous substrate (above saturation for uptake) resulted in an apparent constant specific activity of the metabolic pool through the ripening period. Data from these studies indicated a decline in amino acid incorporation during the climacteric.

It was concluded that the initiation of permeability changes marks the onset of senescence in banana. The causative relations between alterations in permeability, the respiratory rise and other chemical changes attending fruit ripening are discussed.

     

香蕉离体茎尖超低温保存研究

以香蕉(Musaspp.)试管苗为试材,对其离体茎尖小滴玻璃化法超低温保存的影响因素进行了研究。小滴玻璃化法和玻璃化法超低温保存后再生率的差异表明,香蕉更适合用小滴玻璃化法进行超低温保存。香蕉小滴玻璃化法超低温保存的方案如下:试管苗在60g/L蔗糖的MS培养基上培养1~2个月,剥离带有1~2片叶原基的茎尖,室温下装载30m in(可延长至4h),0℃下PVS2处理40~50m in。6个基因型的14个品种的再生率平均为46.9%。通过SSR分子标记检测,再生植株的遗传稳定性没有发生改变。该结果为香蕉种质资源的长期保存提供了理论依据和技术支撑。     

Effect of Abscisic Acid on Banana Fruit Ripening in Relation to the Role of Ethylene

Abstract The role of abscisic acid (ABA) in banana fruit ripening was examined with the ethylene binding inhibitor, 1-methylcyclopropene (1-MCP). ABA (0, 10⁻⁵, 10⁻⁴, or 10⁻³ mol/L) was applied by vacuum infiltration into fruit. 1-MCP (1 μL/L) was applied by injecting a measured volume of stock gas into sealed glass jars containing fruit. Fruit ripening, as judged by ethylene evolution and respiration associated with color change and softening, was accelerated by 10⁻⁴ or 10⁻³ mol/L ABA. ABA at 10⁻⁵ mol/L had no effect. The acceleration of ripening by ABA was greater at 10⁻³ mol/L than at 10⁻⁴ mol/L. ABA-induced acceleration of banana fruit ripening was not observed in 1-MCP treated fruit, especially when ABA was applied after exposure to 1-MCP. Thus, ABA's promotion of ripening in intact banana fruit is at least partially mediated by ethylene. Exposure of ABA-treated fruit to 0.1 μL/L ethylene for 24 h resulted in increased ethylene production and respiration, and associated skin color change and fruit softening. Control fruit (no ABA) was unresponsive to similar ethylene treatments. The data suggest that ABA facilitates initiation and progress in the sequence of ethylene-mediated ripening events, possibly by enhancing the sensitivity to ethylene. Received 29 January 1999; accepted 16 January 2000     

甜瓜乙烯应答因子基因在果实发育成熟过程中的表达特性

根据已报道的甜瓜CMe-ERF1和CMe-ERF2基因cDNA序列设计合成特异性引物,应用RT-PCR技术从甜瓜品种‘河套蜜瓜’成熟果实中克隆得到CMe-ERF1和CMe-ERF2基因cDNA全长编码区序列,分别为498bp和822bp.序列比对分析表明,得到的cDNA序列与已报道的Andes甜瓜相应基因的cDNA序列完全一致.果实不同发育时期实时定量PCR检测结果表明,CMe-ERF1、CMe-ERF2基因表达与甜瓜果实成熟及乙烯生成量显著相关,表明该基因可能对果实成熟起重要作用.     

微生物法生产烷烃研究进展

烷烃在自然界中广泛存在。它不仅是化石能源的主要组成部分,而且在润滑剂、化妆品、水果保藏、植物防护等方面具有广泛的应用价值。本文概述了天然产烷烃的微生物及其烷烃的天然合成途径及其途径中关键酶催化的作用机理,并对近几年国内外运用代谢工程手段改造微生物使其细胞合成烷烃的研究进展作了介绍。微生物生产烷烃可以通过改造烷烃的天然合成菌株或通过在模式微生物中引入异源烷烃合成途径两种方法来强化。最后文章讨论了微生物法生产烷烃存在的不足和今后研究的方向与展望。     

Variation of quercetin glycoside derivatives in three onion (Allium cepa L.) varieties

The aim of this study was to quantify the contents of individual quercetin glycosides in red, yellow and chartreuse onion by High Performance Liquid Chromatography (HPLC) analysis. Acid hydrolysis of individual quercetin glycosides using 6 M hydrochloric acid guided to identify and separate quercetin 7,4′-diglucoside, quercetin 3-glucoside, quercetin 4′-glucoside, and quercetin. The contents of total quercetin glycosides varied extensively among three varieties (ranged from 16.10 to 103.93 mg/g DW). Quercetin was the predominant compound that accounted mean 32.21 mg/g DW in red onion (43.6% of the total) and 127.92 mg/g DW in chartreuse onion (78.3% of the total) followed by quercetin 3-glucoside (28.83 and 24.16 mg/g DW) respectively. Quercetin 3-glucoside levels were much higher in yellow onion (43.85 mg/g DW) followed by quercetin 30.08 mg/g DW. Quercetin 4′-glucoside documented the lowest amount that documented mean 2.4% of the total glycosides. The varied contents of glycosides present in the different onion varieties were significant.     

Metabolic engineering of folate and its precursors in Mexican common bean (Phaseolus vulgaris L.)

Folate (vitamin B9) deficiency causes several health problems globally. However, folate biofortification of major staple crops is one alternative that can be used to improve vitamin intakes in populations at risk. We increased the folate levels in common bean by engineering the pteridine branch required for their biosynthesis. GTP cyclohydrolase I from Arabidopsis (AtGchI) was stably introduced into three common bean Pinto cultivars by particle bombardment. Seed‐specific overexpression of AtGCHI caused significant increases of up to 150‐fold in biosynthetic pteridines in the transformed lines. The pteridine boost enhanced folate levels in raw desiccated seeds by up to threefold (325 μg in a 100 g portion), which would represent 81% of the adult recommended daily allowance. Unexpectedly, the engineering also triggered a general increase in PABA levels, the other folate precursor. This was not observed in previous engineering studies and was probably caused by a feedforward mechanism that remains to be elucidated. Results from this work also show that common bean grains accumulate considerable amounts of oxidized pteridines that might represent products of folate degradation in desiccating seeds. Our study uncovers a probable different regulation of folate homoeostasis in these legume grains than that observed in other engineering works. Legumes are good sources of folates, and this work shows that they can be engineered to accumulate even greater amounts of folate that, when consumed, can improve folate status. Biofortification of common bean with folates and other micronutrients represents a promising strategy to improve the nutritional status of populations around the world.     

Characterization of mannosyl transferases during the pupal instar of Stomoxys calcitrans (L)

Particulate fractions (10,000g) from pupae of Stomoxys calcitrans transfer [¹⁴C]-mannose from GDP-[¹⁴C]-mannose to dolichol monophosphate and proteins. Production of the mannosyl lipid was inhibited by Mn²⁺, UDP, GMP, GDP, and EDTA. The insect growth regulator diflubenzuron had no effect on mannosyl transferase activity. Dolichol monophosphate and Mg²⁺ stimulated mannosyl transferase activity. The mannosyl lipid product was identified as mannosyl-phosphoryl-dolichol (Man-P-Dol). The apparent K_m and V_max values for the formation of Man-P-Dol using GDP-[¹⁴C]-Man while holding dolichol phosphate constant were 2.4 ± 0.9 μM and 9.4 ± 2.3 pmol Man-P-Dol·min^?1·mg^?1 protein, respectively. The apparent K_m and V_max values using dólichol phosphate while holding GDP-Man constant were 2.2 ± 1.2 μM and 18.5 ± 1.7 pmol Man-P-Dol·min^?1·mg^?1 protein.     

Flavonoids from the flowers of Adenium obesum (Forssk.) Roem. & Schult., Mandevilla sanderi (Hemsl.) Woodson,and Nerium oleander L. (Apocynaceae)

Twenty-two ornamental flowers from different Adenium obesum, Mandevilla sanderi, and Nerium oleander cultivars/seedlings were analyzed for the presence of anthocyanins, flavonols, and chlorogenic acid using nuclear magnetic resonance (NMR) and mass spectrometry (MS). Cyanidin 3-O-[6-O-(rhamnosyl)-galactoside] and cyanidin 3-O-(galactoside) were identified as the major and minor anthocyanins, respectively, in three A. obesum seedlings that had red and red-purple flowers.Cyanidin 3-O-[2-O-(xylosyl)-galactoside] was identified as the major anthocyanin, whereas cyanidin 3-O-[6-O-(rhamnosyl)-galactoside] and cyanidin 3-O-(galactoside) were identified as the minor anthocyanins in 8 M. sanderi cultivars that had red and red-purple flowers. Cyanidin 3-O-[6-O-(rhamnosyl)-galactoside] and cyanidin 3-O-(galactoside) were identified as the major anthocyanins, whereas cyanidin 3-O-[2-O-(xylosyl)-galactoside] was identified as the minor anthocyanin in 8 N. oleander cultivars with red and red-purple flowers. Low levels of anthocyanins were detected in the N. oleander and M. sanderi cultivars that had white flowers, and there were no anthocyanins detected in the N. oleander cultivars with yellow flowers. Chlorogenic acid and four flavonols, quercetin 3-O-[6-O-(rhamnosyl)-galactoside], quercetin 3-O-[6-O-(rhamnosyl)-glucoside], kaempferol 3-O-(galactoside), and kaempferol 3-O-[6-O-(rhamnosyl)-galactoside], were identified in the flowers from all 22 cultivars/seedlings investigated.     

Molecular characterization of S-RNase genes and S-genotypes in the Japanese apricot (Prunus mume Sieb. et Zucc.)

Three partial S-RNase genes, MSRN-1, MSRN-2, and MSRN-3, in the Japanese apricot (Prunus mume Sieb. et Zucc.) were isolated from the three cultivars Nankou, Gyokuei, and Kairyouuchidaume, respectively. The structural characteristics revealed that S-RNase genes from the Japanese apricot were in the T2/SRNase-type S-RNase family with five conserved regions (C1, C2, C3, RC4, and C5) and one variable region (RHV) as reported in the other rosaceous plants. In the phylogenetic tree of T2/S SRNase-type RNases, three S-RNase genes of the Japanese apricot did not form a species-specific subgroup but the Prunus subfamily did. At least seven S-allelic genes were present in the Japanese apricot, and S-genotypes of six representative cultivars, including Nankou, Gyokuei, Kairyouuchidaume, Baigou, Kagajizou, and Oushuku were first established in this study as S ₁ S ₇, S ₂ S ₆, S ₃ S ₄, S ₃ S ₆, S ₃ S ₆ and S ₁ S ₅, respectively. An extended elucidation of the S-genotype would contribute to a more efficient breeding program of the Japanese apricot. Received: 5 September 2000 / Revision accepted: 22 December 2000     

Metabolic and genetic perturbations accompany the modification of galactomannan in seeds of Medicago truncatula expressing mannan synthase from guar (Cyamopsis tetragonoloba L.)

Galactomannan gums are widely used in the food and oil industries, and there is considerable interest in applying biotechnological approaches to improve their physical properties. A mannan synthase from guar ( Cyamopsis tetragonoloba ) was expressed under the control of a bean β-phaseolin promoter in transgenic Medicago truncatula . Although the expression of exogenous mannan synthase caused a slight decrease in galactomannan levels in Medicago , the molecular weight and viscosity of the polymer were significantly increased, although the mannose to galactose ratio and degree of polydispersity remained unchanged. At the same time, expression of about 2.8% of the genes was altered significantly in the seeds of transgenic Medicago lines analysed by Affymetrix genome chip, with a particularly striking induction of putative trehalose phosphate synthase genes. Mannan synthase expression also caused large alterations in the levels of a number of sugars and sugar alcohols, suggesting that over-expression of a processive glycosyltransferase perturbs the mechanisms of sugar sensing and/or homeostasis, possibly involving signalling via trehalose-6-phosphate.     

Relationship between Ripening and the Development of Banana Anthracnose Caused by Colletotrichum musae (Berck. and Curt.) Arx

Wound anthracnose caused by Colletotrichum musae is the main disease affecting the quality of export bananas from the French Antilles. Little is known about the effects of ethylene on the development of wound anthracnose and quiescent anthracnose. The results of our experiments with 1‐methylcyclopropene (1‐MCP), an ethylene receptor site inhibitor, clearly revealed that ethylene was not directly involved in triggering rot development. Quiescent anthracnose symptoms were found to appear only after bananas began ripening. In contrast, wound anthracnose developed just as quickly in ‘green 1‐MCP‐treated bananas’ as in ‘yellow ripening bananas’. In cases of wound anthracnose, contrary to quiescent anthracnose, rot development was not dependent on the extent of peel ripeness.     

Microbial community structure changes during Aroclor 1242 degradation in the rhizosphere of ryegrass (Lolium multiflorum L.)

Polychlorinated biphenyls in a commercial mixture (Aroclor 1242) were added to soil at 8.0 mg kg⁻¹ with and without ryegrass ( Lolium multiflorum L.) planted in a specially designed rhizobox. At the end of 90 days, the presence of plants significantly increased Aroclor 1242 degradation compared with soils without ryegrass. Phospholipid fatty acids (PLFAs) profiles were affected by the distance from the rhizosphere, indicating a distance-dependent selective enrichment of competent species that may be responsible for efficient Aroclor 1242 degradation. The highest concentration of total PLFAs also occurred at 3 mm from the root zone in planted soils. The numbers of bacteria (cy17:0, 16:0), gram-positive bacteria (a15:0, i16:1, a17:0) and actinomycete (18:2ω6,9c) were significantly higher in planted soils than in unplanted soils. Furthermore, individual PLFAs [i16:0, 16:0 N alcohol, 18:0(10Me), i16:1, a15:0, i14:1, 14:0 2OH, 18:1ω9c, a17:0, 14:0 3OH, i14:0, a16:0, 16:1ω5c] were strongly correlated with the Aroclor 1242 degradation rates (%) ( P <0.05) in planted treatments, whereas individual PLFAs of i16:1, 12:0 3OH, 15:0, a15:0 had significant correlations with the Aroclor 1242 degradation rates (%) ( P <0.05) in unplanted soils. In particular, individual PLFAs i16:1 had strong correlations with Aroclor 1242 degradation in treatments both with and without ryegrass.