Mature Green Tomato Fruit Research Articles

Comparison of Ripening Processes in Intact Tomato Fruit and Excised Pericarp Discs

Physiological processes characteristic of ripening in tissues of intact tomato fruit (Lycopersicon esculentum Mill.) were examined in excised pericarp discs. Pericarp discs were prepared from mature-green tomato fruit and stored in 24-well culture plates, in which individual discs could be monitored for color change, ethylene biosynthesis, and respiration, and selected for cell wall analysis. Within the context of these preparation and handling procedures, most whole fruit ripening processes were maintained in pericarp discs. Pericarp discs and matched intact fruit passed through the same skin color stages at similar rates, as expressed in the L(*)a(*)b(*) color space, changing from green (a(*) < -5) to red (a(*) > 15) in about 6 days. Individual tissues of the pericarp discs changed color in the same sequence seen in intact fruit (exocarp, endocarp, then vascular parenchyma). Discs from different areas changed in the same spatial sequence seen in intact fruit (bottom, middle, top). Pericarp discs exhibited climacteric increases in ethylene biosynthesis and CO(2) production comparable with those seen in intact fruit, but these were more tightly linked to rate of color change, reaching a peak around a(*) = 5. Tomato pericarp discs decreased in firmness as color changed. Cell wall carbohydrate composition changed with color as in intact fruit: the quantity of water-soluble pectin eluted from the starch-free alcohol insoluble substances steadily increased and more tightly bound, water-insoluble, pectin decreased in inverse relationship. The cell wall content of the neutral sugars arabinose, rhamnose, and galactose steadily decreased as color changed. The extractable activity of specific cell wall hydrolases changed as in intact fruit: polygalacturonase activity, not detectable in green discs (a(*) = -5), appeared as discs turned yellow-red (a(*) = 5), and increased another eight-fold as discs became full red (a(*) value +20). Carboxymethyl-cellulase activity, low in extracts from green discs, increased about six-fold as discs changed from yellow (a(*) = 0) to red.

Characteristics of a Membrane-Associated Lipoxygenase in Tomato Fruit

Microsomal membranes isolated from the pericarp of maturegreen tomato (Lycopersicon esculentum) fruit rapidly metabolize exogenous radiolabeled linoleic acid into fatty acid oxidation products at 22 degrees C. The reaction is strongly inhibited by n-propyl gallate, an inhibitor of lipoxygenase. The membranes also rapidly metabolize 16:0/18:2(*) phosphatidylcholine into radiolabeled oxidation products that comigrate on TLC plates with those formed from free linoleic acid. At 30 degrees C, the formation of fatty acid oxidation products from 16:0/18:2(*) phosphatidylcholine is slower, and there is an initial accumulation of radiolabeled linoleic acid that is not evident at 22 degrees C, which can be attributed to the action of lipolytic acyl hydrolase. Radiolabeled phosphatidic acid and diacylglycerol are also formed during metabolism of 16:0/18:2(*) phosphatidylcholine by the microsomal membranes, and there is no breakdown of either linoleic acid or phosphatidylcholine by heat-denatured membranes. When Triton X-100 treated membranes were used, the same patterns of metabolite formation from radiolabeled linoleic acid and 16:0/18:2(*) phosphatidylcholine were observed. Thus, the enzymes mediating the breakdown of these radiolabeled compounds appear to be tightly associated with the membranes. Collectively, the data indicate that there is a lipoxygenase associated with microsomal membranes from tomato fruit that utilizes free fatty acid substrate released from phospholipids. The microsomal lipoxygenase is strongly active over a pH range of 4.5 to 8.0, comprises approximately 38% of the total (microsomal plus soluble) lipoxygenase activity in the tissue, has an apparent K(m) of 0.52 millimolar and an apparent V(max) of 0.186 millimoles per minute per milligram of protein. The membranous enzyme also cross-reacts with polyclonal antibodies raised against soybean lipoxygenase-1 and has an apparent molecular mass of 100 kilodaltons.

Abscisic Acid Content in Chilled Tomato Fruit

Free abscisic acid (ABA) was determined in pericarp of mature-green tomato fruit before and after chilling at 2C for 12 days, in chilling-sensitive and chilling-tolerant cultivars. After being ripened at 20C, these fruit were compared with field-ripened fruit. Chilled fruit contained 2 to 3 times the amount of free ABA as did unchilled. The ABA isolation method described involves the use of preparative and analytical high performance liquid chromatography followed by gas chromatography.

Physical and Biochemical Changes in the Microsomal Membranes of Tomato Fruit Associated with Acclimation to Chilling

Summary Mature green tomato fruit ( Lycopersicon esculentum L. cv. Caruso) were acclimated to cold temperatures and their physiological properties compared to chilled and ripening fruit. Spin labelling studies on isolated microsomal membranes showed shifts to higher breakpoint temperatures from the initial 11–12 °C in the spin label motion parameter vs. temperature plots for the chilled and ripened fruit membranes; breakpoint temperature for the acclimated fruit shifted upwards initially and decreased to 8 °C after 15 days of acclimation. No changes were observed in the average fluidity of the membranes. Energy of activation (Ea) for ATP hydrolysis at low temperatures (5–17.5 °C) increased for the three treatments; however, after 15 days the Ea for the acclimating membranes was lower than for the chilled and ripening membranes. Over the duration of storage and for fruit from all treatments, changes in the expression of membrane associated proteins were observed. No changes were observed in the relative proportions of membrane phospholipids or fatty acids. Ultrastructural studies indicated microvesiculation of the endoplasmic reticulum (ER) and disruption of the ER lamellae due to chilling. Acclimating cells showed «budding off» of larger membrane vesicles, which may constitute a «retailoring» process responsible for increased chilling tolerance.

Ultrastructural Changes Associated with Chilling Injury in Mature-green Tomato Fruit

Abstract The effect of low temperature on cell ultrastructure was investigated in chilling-sensitive and chilling-resistant tomato fruit (Lycopersicon esculentum Mill.) Damage to the chilling-sensitive cultivar included microvesiculation of the endoplasmic reticulum and loss of ribosomes, chloroplast, and mitochondrial swelling; loss of starch granules; disorganization of the internal lamellae of chloroplasts; grana unstacking, as well as plastoglobuli and tonoplast degradation. Only a slight disorganization of the internal chloroplast lamellae was evident in the resistant species after 7 days at 5C. The primary site of damage appeared to be the chloroplast in both chilling-sensitive and -resistant species. The ultrastructural damage observed could be explained in terms of membrane disruption.

21. Textural and Enzymatic Studies of the Effects of Chilling Temperatures on the Ripening Process in Mature Green Tomato Fruit

21. Textural and Enzymatic Studies of the Effects of Chilling Temperatures on the Ripening Process in Mature Green Tomato Fruit

Effect of Alcohols and Their Interaction with Ethylene on the Ripening of Epidermal Pericarp Discs of Tomato Fruit

Ethanol concentrations that were induced in pericarp discs of mature-green tomato fruit (Lycopersicon esculentum Mill, cv Castlemart) either by anaerobic metabolism or by exposure to ethanol vapor inhibited ripening without increasing the rate of ion leakage. Inhibition of ripening (i.e. lycopene synthesis) of excised tomato pericarp tissue by ethanol vapor was reversed by increasing concentrations of the plant hormone ethylene. A Lineweaver-Burk plot indicated noncompetitive interaction between ethanol and ethylene. Methanol and n-propanol also inhibited lycopene synthesis without significantly increasing ion leakage. The similar inhibitory effects of methanol, ethanol, and n-propanol at concentrations which did not stimulate ion leakage, and the relationship between activity and lipophilia of the alcohols suggest that their mode of action was through disruption of membranes associated with ethylene action.

Microstructual Evaluation of Chilling Injury in Mature Green Tomato Fruit

The effects of low, but non-freezing temperatures on the microstructure of mature green tomato pericarp tissue were studied by scanning electron microscopy (SEM) and brightfield and epifluorescent light microscopy (LM). Pit microstructure was studied by SEM showing that dehydration may be an important factor in the development of this defect. Brightfield LM showed cell shrinkage and a disorganization of subcellular structure while epifluorescent LM of Calcofluor White stained cell walls showed a decrease in the fluorescence intensity due to chilling, suggesting cell wall or middle lamella breakdown. Optimum fixation conditions for tomato fruit tissue are described.

Ripening of Mature-green Tomato Fruit Slices

Abstract In the article “Ripening of Mature-green Tomato Fruit Slices”, by Fabio Mencarelli and Mikal E. Saltveit, Jr. [J. Amer. Soc. Hort. Sci. 113(5):742−745, September 1988], Table 4 is called out in the next-to-last paragraph. There is no Table 4 in this article.

Ripening of Mature-green Tomato Fruit Slices

Abstract Equatorial 7-mm-thick slices of mature-green tomato fruit (Lycopersicon esculentum, Mill., cv. Castlemart) ripened normally, and changes in the concentrations of lycopene, soluble solids content, and titratable acids and in pH were analogous to, although in some cases significantly different from, changes in whole fruit that were harvested when mature-green and ripened. An untrained taste panel scored ripened slices acceptable to good, and no off-flavors were detected. Slices of mature-green tomato fruit can be ripened to an acceptable level of quality, and could provide an additional outlet for fresh-market tomatoes to the home and institutional markets.

Quick-freeze differential scanning calorimetry and saturation transfer electron spin resonance: Novel techniques for assessing phase transitions in biological membranes

Quick-freeze differential scanning calorimetry (QF-DSC) and saturation transfer-electron spin resonance (ST-ESR) spectroscopy were used to study lipid gel-phase transitions in mature green tomato fruit microsomal membranes. ST-ESR of 12-doxyl methyl stearate labelled membranes proved to be reproducible and provided increased sensitivity to temperature-induced structural changes, allowing the detection of several transitions in isolated membranes (6 degrees C, 21 degrees C, 28 degrees C). QF-DSC led to the assessment of lipid gel phase transitions in isolated microsomal membranes and microsomal membrane lipids by enhancing the transition. A phase transition enthalpy of 114 J/g and an onset temperature of 29.8 degrees C were obtained for whole membranes while with isolated lipids values of 370 J/g and 19.9 degrees C were found.

Transport Properties of the Tomato Fruit Tonoplast

An anion-sensitive H(+)-translocating ATPase was identified in membrane vesicles isolated from mature green tomato (Lycopersicon esculentum) fruit. The H(+)-ATPase was associated with a low density membrane population having a peak density of 1.11 grams per cubic centimeter, and its activity was inhibited by NO(3) (-), N,N'-dicyclohexylcarbodiimide and diethylstilbestrol but not by vanadate, azide, molybdate, or oligomycin. This H(+)-ATPase has an unusual pH dependence indicating both a slightly acidic and a near neutral peak of activity. Chloride was found to be a potent stimulator of ATPase activity. The K(m) for the H(+)-ATPase was approximately 0.8 millimolar ATP. The characteristics of this H(+)-ATPase are very similar to those described for a number of plant cell tonoplast H(+)-ATPases suggesting that the activity identified in tomato fruit membranes is tonoplast-associated. This report demonstrates the feasibility of isolating tonoplast vesicles from acidic fruit tissues for studies of transport activities associated with fruit development and maturation.

Effect of Silver Ions on Ethylene Biosynthesis by Tomato Fruit Tissue

Mature-green tomato fruit (Lycopersicon esculentum Mill.) were treated asymmetrically with 2 millimolar silver thiosulfate (STS) through a cut portion of the peduncle while still attached to the plant. One-half of the fruit received silver and remained green while the other half ripened normally and was silver-free (less than 0.01 parts per billion). Harvested mature-green fruit were also treated with STS through the cut pedicel. Green tissue from silver-treated fruit had levels of 1-aminocyclopropane-1-carboxylic acid (ACC, the immediate ethylene precursor) slightly less or similar to that of turning or red-ripe tissue from the same fruit, and similar to that of mature-green tissue from control fruit. Ethylene production was higher in green tissue from silver-treated fruit than from either red tissue from the same fruit, or mature-green tissue from control fruit. By inhibiting ACC synthesis with aminoethoxyvinyl glycine, and by applying ACC +/- silver to excised disks of pericarp tissue from control or silver-treated tomatoes, we showed that short-term silver treatment did not affect the biological conversion of ACC to ethylene, while long-term treatment stimulated both the conversion of ACC to ethylene and the synthesis of ACC.

CYTOKININ ([8 -14C]BENZYLAMINOPURINE) METABOLISM IN MATURE GREEN TOMATO PERICARP

Cytokinin ([8–14C]Benzylaminopurine), (BA), metabolism in mature green tomato fruit (Lycopersicon esculentum Mill Hybrid “Ohio CR-6”) was monitored. Radiotracer studies of [8–14C]BA metabolism indicated the rapid formation of more polar metabolites. Alkaline phosphatase treatment indicated at least two of the metabolites to be phosphorylated. Mass spectral data showed that the TMS derivative of one metabolite contained a sugar moiety of the β-D-glucopyranose tetra TMS form but lacked characteristic fragments corresponding to the N6 benzyl side-chain or intact purine ring. A major radioactive peak slightly more polar in character than the parent compound [8–14C]BA was also observed.

Promotion of Ethylene Evolution and Ripening of Tomato Fruit by Galactose

Mature green tomato fruit (Lycopersicon esculentum Mill. cv ;Rutgers') were infiltrated with 0.5 milliliters of sterilized, distilled water alone, or containing enough glucose or galactose to allow for a concentration of 400 micrograms per gram fresh weight after infiltration. All fruit showed a transient peak of ethylene production within 6 hours due to the slight wounding by vacuum infiltration. In addition, galactose-treated fruit underwent a temporal increase in ethylene production after 25 hours, whereas, the glucose and H(2)O-control fruit did not. Furit infiltrated with galactose subsequently produced ethylene and ripened substantially earlier than glucose or H(2)O-control fruit.

Initiation of Tomato Fruit Ripening with Copper

Abstract A vacuum infiltration technique that allowed precise control of both infiltration rate and amount of solution administered to whole tomato (Lycopersicon esculentum) fruit was developed. Controlled volumes of 5 mm solutions of CuSO4, Cu(NO3)2, HgCl2, CaSO4, KNO3, (NH4)2C2O4, Na2HPO4, citrate and 1 mm EDTA or EGTA were infiltrated into intact, mature-green tomato fruit and evaluated with regard to their effect on the pattern of tomato ripening. Copper significantly accelerated lycopene accumulation and influenced both the timing and magnitude of climacteric ethylene production. Infiltration with HgCl2 elicited similar effects as copper, but severe phytotoxicity was observed. In contrast, CaSO4, KNO3, and chelators had no significant effect on the pattern of ripening. Copper initiated wound ethylene production in the ripening mutant rin that reached up to 50% of the wound levels observed in normal fruit, but rin was not induced to ripen.

The Inhibition of Tomato Fruit Ripening by Silver

Mature green tomato fruit, infiltrated with STS (up to 10 μmol) while still attached to the plant, ripened unevenly to give extensive green areas on an otherwise red background. Pericarp wall tissue from the two contrasting areas was analysed for various organic constituents. Both the green and, to a certain extent, the red tissue from treated fruit showed differences from normal in AIS, acidity, and PE activity. PG activity, which usually increases rapidly as tomatoes ripen, was low in the green but not significantly different from normal in the red tissue from STS-treated fruit. TEM examination revealed that electron-dense particles were present in the cell walls of phloem elements in vascular bundles of the green tissue, but these deposits were not found in the red tissue from the same fruit. X-ray microanalysis of the particles suggested that they contained concentrations of silver and sulphur. The results are interpreted as suggesting that silver is affecting those sites in the cell that would subsequently be involved in promoting the synthesis of PG.

Changes in Ribosome Organization and Messenger RNA Abundance in Ripening Tomato Fruits

The involvement of RNA and protein synthesis in fruit ripening was investigated. Mature-green tomato fruits were found to contain about 30% of their ribosomal RNA in polyribosomes. At the 'breaker' or early ripening stage, about 50% of rRNA was in polyribosomes and this distribution of rRNA was maintained until fruits were fully ripe. The continued presence of polyribosomes is consistent with active protein synthesis persisting through and beyond the climacteric period when the wall-hydrolysing enzyme polygalacturonase accumulates and fruits soften, synthesize lycopene and undergo other ripening related changes. Poly(A)-containing RNA purified from polyribosomes extracted from individual fruits was used to prime the synthesis of [35S]methionine-labelled polypeptides by a wheat germ in vitro translation system. The pattern of polypeptides synthesized in response to RNA from mature-green fruits differed from that given by RNA from ripening fruits. The majority of changes were found to occur within approximately 48 h of the increase of ethylene synthesis and were apparent in all fruits with any pink or red colour. Similar results were obtained by translating total cellular RNA and total polyribosomal RNA indicating that the major RNA species shown in this study to change in abundance during ripening are polyadenylated, and hence most probably cytoplasmic, and do not accumulate as 'stored messages' outside of the polyribosomes. The differences between green and ripening fruits in polyribosome profiles were demonstrated in two cultivars of tomato. Differences in mRNA populations between green and ripe fruits were found in three cultivars.

Changes in colour, polygalacturonase monosaccharides and organic acids during storage of tomatoes

The appearance of polygalacturonase and red pigmentation in mature-green tomato fruit was prevented by storing the fruit in 5% O 2, 5% CO 2 and 90% N 2. However, the breakdown of starch to give monosaccharides and the change in concentration of organic acids which is normally associated with ripening still took place. On removal of the fruit to ambient conditions, polygalacturonase was synthesized and the fruit changed colour but monosaccharide and organic acid concentrations did not change.

Superoxide dismutase: A possible protective agent against sunscald in tomatoes (lycopersicon esculentum mill.)

Superoxide dismutase (SOD, EC 1.15.1.1) was concentrated from mature-green tomato fruits by gel chromatography. The enzyme was inhibited by cyanide but not by chloroform-ethanol, and appears to contain zinc and lesser amounts of copper. SOD-activity levels were high in immature green fruits, declined to a minimum in the mature-green and breaker stages known to be most susceptible to sunscald damage, increased again until the fruits were pink, and finally decreased through the red-ripe and overripe stages to the level of the mature-green fruit. When tolerance to sunscald damage was induced in mature-green fruits by controlled temperature treatment and samples of the fruits were challenged at various times during this process with a combined heat-and-light treatment known to cause sunscald, SOD activity was found to be inversely related to the susceptibility of the fruit to sunscald damage. It is suggested that superoxide is involved in sunscald injury to tomatoes and that tolerance is acquired through increases in SOD activity. Possibly SOD acts as a general protective agent against photodynamic damage to green tissues in plants that have become conditioned as the result of normal diurnal temperature fluctuations.