Non-invasive photoacoustic spectroscopic determination of relative endogenous nitric oxide and ethylene content stoichiometry during the ripening of strawberries Fragaria anannasa (Duch.) and avocados Persea americana (Mill.)

Employing non-invasive photoacoustic spectrometry, emissions of nitric oxide (NO) and ethylene in post-harvest strawberries and avocados were monitored. A clear-cut stoichiometric relationship was found between the two gases: unripe fruit manifesting high NO and low ethylene levels-the converse in ripe fruit. Findings are discussed in the light of putative control of ethylene-promoted fruit senescence by endogenous NO.

The regulation of 1-aminocyclopropane-1-carboxylic acid synthase gene expression during the transition from system-1 to system-2 ethylene synthesis in tomato

1-Aminocyclopropane-1-carboxylic acid synthase (ACS) is one of the key regulatory enzymes involved in the synthesis of the hormone ethylene and is encoded by a multigene family containing at least eight members in tomato (Lycopersicon esculentum). Increased ethylene production accompanies ripening in tomato, and this coincides with a change in the regulation of ethylene synthesis from auto-inhibitory to autostimulatory. The signaling pathways that operate to bring about this transition from so-called system-1 to system-2 ethylene production are unknown, and we have begun to address these by investigating the regulation of ACS expression during ripening. Transcripts corresponding to four ACS genes, LEACS1A, LEACS2, LEACS4, and LEACS6, were detected in tomato fruit, and expression analysis using the ripening inhibitor (rin) mutant in combination with ethylene treatments and the Never-ripe (Nr) mutant has demonstrated that each is regulated in a unique way. A proposed model suggests that system-1 ethylene is regulated by the expression of LEACS1A and LEACS6. In fruit a transition period occurs in which the RIN gene plays a pivotal role leading to increased expression of LEACS1A and induction of LEACS4. System-2 ethylene synthesis is subsequently initiated and maintained by ethylene-dependent induction of LEACS2.

Isolation of cDNA clones corresponding to genes expressed during fruit ripening in Japanese pear (Pyrus pyrifolia Nakai): involvement of the ethylene signal transduction pathway in their expression

Thirty cDNA clones of genes corresponding to mRNAs up-regulated during fruit ripening of Japanese pear (Pyrus pyrifolia Nakai cv. Kikusui) were obtained by differential screening of a ripe fruit cDNA library. All of these cDNAs were sequenced and gathered into 11 non-redundant groups after database searches. These clones represented genes associated with stress responses, protein catabolism or pathogenesis. The accumulation of transcripts of 3 out of 11 genes was inhibited by 1-methylcyclopropene (MCP), an inhibitor of ethylene action.

[Seed abortion in Enterolobium cyclocarpum (Mimosidae): effect of relative position in the fruit]

We examined if seed abortion in Guanacaste free fruits (Enterolobium cyclocarpum) is related to position within fruits, by establishing the abortion ratio in 150 fruits from 10 trees, collected in Santa Rosa National Park (Guanacaste, Costa Rica). Fruits were divided in basal, central and distal sections. We found marginal differences in abortion ratio between these sections (Anova, p = 0.058), and also among trees (p = 0.01). In general, the distal section had the greatest abortion ratio in relation to other sections. This abortion pattern could be caused by resource competition within siblings and not by genetic differences among them.

Pomegranate juice consumption reduces oxidative stress, atherogenic modifications to LDL, and platelet aggregation: studies in humans and in atherosclerotic apolipoprotein E-deficient mice

BACKGROUND

Dietary supplementation with nutrients rich in antioxidants is associated with inhibition of atherogenic modifications to LDL, macrophage foam cell formation, and atherosclerosis. Pomegranates are a source of polyphenols and other antioxidants.

OBJECTIVE

We analyzed, in healthy male volunteers and in atherosclerotic apolipoprotein E-deficient (E(0)) mice, the effect of pomegranate juice consumption on lipoprotein oxidation, aggregation, and retention; macrophage atherogenicity; platelet aggregation; and atherosclerosis.

DESIGN

Potent antioxidative effects of pomegranate juice against lipid peroxidation in whole plasma and in isolated lipoproteins (HDL and LDL) were assessed in humans and in E(0) mice after pomegranate juice consumption for </=2 and 14 wk, respectively.

RESULTS

In humans, pomegranate juice consumption decreased LDL susceptibility to aggregation and retention and increased the activity of serum paraoxonase (an HDL-associated esterase that can protect against lipid peroxidation) by 20%. In E(0) mice, oxidation of LDL by peritoneal macrophages was reduced by up to 90% after pomegranate juice consumption and this effect was associated with reduced cellular lipid peroxidation and superoxide release. The uptake of oxidized LDL and native LDL by mouse peritoneal macrophages obtained after pomegranate juice administration was reduced by 20%. Finally, pomegranate juice supplementation of E(0) mice reduced the size of their atherosclerotic lesions by 44% and also the number of foam cells compared with control E(0) mice supplemented with water.

CONCLUSION

Pomegranate juice had potent antiatherogenic effects in healthy humans and in atherosclerotic mice that may be attributable to its antioxidative properties.

Effects of short episodes of heat stress on flower production and fruit-set of groundnut (Arachis hypogaea L.)

Groundnuts (Arachis hypogaea L.) are an important crop of the semi-arid tropics where they are often exposed to maximum temperatures of > 40 degrees C for short periods during the growing season. The objectives of this study were to determine: (i) the effects of short periods of exposure to high temperature on flower production (FN), the proportion of flowers forming fruits (fruit-set) and the number of pegs and pods per plant (RNt); (ii) whether fruit-set is affected by high temperature during different periods of daylight in each diurnal cycle; and (iii) whether responses to temperature were qualitative or quantitative. Plants of cv. ICGV 86015 were grown in controlled environments at a day/night temperature of 28/22 degrees C from sowing until 9 d after flowering (DAF). Then, cohorts of plants were: (a) exposed to day temperature of 28, 34, 42 or 48 degrees C for 2, 4 or 6 d; or were (b) exposed to 34, 42 or 48 degrees C for 6 d either throughout a 12 h day (08.00 to 20.00 h, WD), or only during the first 6 h (AM) or second 6 h (PM) of the day. Values of RNt were significantly reduced by high temperature, by duration of exposure, and by timing of exposure. Variation in FN was quantitatively related to floral bud temperatures during the day over the range 28-43 degrees C. In contrast, only floral bud temperatures > 36 degrees C during AM and WD significantly reduced fruit-set and hence RNt, whereas high PM temperature had no effect on fruit-set. These findings indicate that the response of RNt to day temperature is quantitative and can be modelled by combining the responses of FN and fruit-set to temperature.

Effects of short episodes of heat stress on flower production and fruit-set of groundnut (Arachis hypogaea L.)

Groundnuts (Arachis hypogaea L.) are an important crop of the semi-arid tropics where they are often exposed to maximum temperatures of > 40 degrees C for short periods during the growing season. The objectives of this study were to determine: (i) the effects of short periods of exposure to high temperature on flower production (FN), the proportion of flowers forming fruits (fruit-set) and the number of pegs and pods per plant (RNt); (ii) whether fruit-set is affected by high temperature during different periods of daylight in each diurnal cycle; and (iii) whether responses to temperature were qualitative or quantitative. Plants of cv. ICGV 86015 were grown in controlled environments at a day/night temperature of 28/22 degrees C from sowing until 9 d after flowering (DAF). Then, cohorts of plants were: (a) exposed to day temperature of 28, 34, 42 or 48 degrees C for 2, 4 or 6 d; or were (b) exposed to 34, 42 or 48 degrees C for 6 d either throughout a 12 h day (08.00 to 20.00 h, WD), or only during the first 6 h (AM) or second 6 h (PM) of the day. Values of RNt were significantly reduced by high temperature, by duration of exposure, and by timing of exposure. Variation in FN was quantitatively related to floral bud temperatures during the day over the range 28-43 degrees C. In contrast, only floral bud temperatures > 36 degrees C during AM and WD significantly reduced fruit-set and hence RNt, whereas high PM temperature had no effect on fruit-set. These findings indicate that the response of RNt to day temperature is quantitative and can be modelled by combining the responses of FN and fruit-set to temperature.

Determination of avocado and mango fruit properties by ultrasonic technique

A nondestructive ultrasonic measurement system was developed for the assessment of some transmission parameters which might have quantitative relations with the maturity, firmness and other quality-related properties of avocado and mango fruits. The system utilizes a set of low-frequency probes arranged to measure the ultrasonic signal transmitted and received over a short distance across the peel. The attenuation of the ultrasonic waves, transmitted through the peel and the attached fruit tissue, changes as a result of the progressive ripening and softening of the fruit during the fruiting season and in the course of storage. The present study quantitatively addressed the linkage between the ultrasonic attenuation and the physiological parameters of the flesh of the fruits. Results were obtained in the time and frequency domain, and the data set was analyzed statistically to identify the relations between the major physiological indices and the ultrasonic parameters. Quantitative relations were developed to describe the linkage between ultrasonic parameters and the maturity, firmness and other quality-related properties in mango and avocado fruits.

Determination of the rate of photoreduction of O2 in the water-water cycle in watermelon leaves and enhancement of the rate by limitation of photosynthesis

A study was performed to determine how the electron fluxes for the photosynthetic carbon reduction (PCR) and the photorespiratory carbon oxidation (PCO) cycles affect the photoreduction of O2 at PSI, which is the limiting step in the water-water cycle. Simultaneous measurements were made of CO2-gas exchange, transpiration and quantum yield of PSII [phi(PSII)] using leaves of watermelon (Citrullus lanatus). The total electron flux in PSII[Je(PSII)], as estimated from phi(PSII), was always larger than the total electron flux required for the PCR and PCO cycles at various partial pressures of CO2 and O2 and 1,100 micromol photons m(-2)s(-1). This observation suggested the existence of an alternative electron flux (Ja). Ja was divided into O2-dependent [Ja(O2-depend)] and O2-independent [Ja(O2-independ)] components. The magnitude of half Ja(O2-depend), 7.5 to 9.5 micromol e- m(-2)s(-1), and its apparent Km for O2, about 8.0 kPa, could be accounted for by the photoreduction of O2 at PSI either mediated by ferredoxin or catalyzed by monodehydroascorbate reductase. The results indicated that Ja(O2-depend) was driven by the water-water cycle. A decrease in the intercellular partial pressure of CO2 from 23 to 5.0 Pa at 21 kPa O2 enhanced Ja(O2-depend) by a factor of 1.3. Saturation of the activities of both the PCR and PCO cycles by increasing the photon flux density induced Ja. These results indicate the electron flux in PSII that exceeds the flux required for the PCR and PCO cycles induces the photoreduction of O2 in the water-water cycle.

Endo-beta-mannanase activity increases in the skin and outer pericarp of tomato fruits during ripening

Activity of endo-beta-mannanase increases during ripening of tomato (Lycopersicon esculentum Mill.) fruit of the cultivar Trust. beta-Mannoside mannohydrolase is also present during ripening, but its pattern of activity is different from that of endo-beta-mannanase. The increase in endo-beta-mannanase activity is greatest in the skin, and less in the outer and inner pericarp regions. This enzyme is probably bound to the walls of the outermost cell layers of the fruit during ripening, and it requires a high-salt buffer for effective extraction. The enzyme protein, as detected immunologically on Western blots, is present during the early stages of ripening, before any enzyme activity is detectable. The mRNA for the enzyme is also present at these stages; endo-beta-mannanase may be produced and sequestered in a mature-sized inactive form during early ripening. Most non-ripening mutants of tomato exhibit reduced softening and lower endo-beta-mannanase activity, but a cause-and-effect relationship between the enzyme and ripening is unlikely because some cultivars which ripen normally do not exhibit any endo-beta-mannanase activity in the fruit.

An expansin gene expressed in ripening strawberry fruit

Tissue softening accompanies the ripening of many fruit and initiates the processes of irreversible deterioration. Expansins are plant cell wall proteins proposed to disrupt hydrogen bonds within the cell wall polymer matrix. Expression of specific expansin genes has been observed in tomato (Lycopersicon esculentum) meristems, expanding tissues, and ripening fruit. It has been proposed that a tomato ripening-regulated expansin might contribute to cell wall polymer disassembly and fruit softening by increasing the accessibility of specific cell wall polymers to hydrolase action. To assess whether ripening-regulated expansins are present in all ripening fruit, we examined expansin gene expression in strawberry (Fragaria x ananassa Duch.). Strawberry differs significantly from tomato in that the fruit is derived from receptacle rather than ovary tissue and strawberry is non-climacteric. A full-length cDNA encoding a ripening-regulated expansin, FaExp2, was isolated from strawberry fruit. The deduced amino acid sequence of FaExp2 is most closely related to an expansin expressed in early tomato development and to expansins expressed in apricot fruit rather than the previously identified tomato ripening-regulated expansin, LeExp1. Nearly all previously identified ripening-regulated genes in strawberry are negatively regulated by auxin. Surprisingly, FaExp2 expression was largely unaffected by auxin. Overall, our results suggest that expansins are a common component of ripening and that non-climacteric signals other than auxin may coordinate the onset of ripening in strawberry.

[Vegetable resources with agroindustrial potential from Guatemala. Chemical characterization of the pulp and of the seeds of Theobroma bicolor]

T. bicolor grows wild in certain regions of Guatemala. The fruit is utilized by the rural population for the preparation of drinks from the pulp and the seed, replacing cocoa (T. cocoa). The fruit of T. bicolor used in the present study, measured on the average, 15 cm long and had an average weight, of 752 g. The pulp, the shell, and the seed represented 23.8, 62.5, and 13.7%, respectively, of the fruit weight. The pulp contained on the average, 38 seeds/fruit, which weighted on the average, 1.11 g and were 2.4 cm long. T. cacao seeds weighted 0.62 g and were 1.6 cm long. The protein content (24.42%) and fiber content (30.86%) of the T. bicolor seeds, was greater than those from T. cacao, although fat content was lower (25.48%). The fat of the seeds of T. bicolor has different physicochemical characteristics than the fat of the seeds of T. cacao, such as melting point, iodine value, and saponification number. The seeds of both, T. cacao and T. bicolor, were used for the preparation of a local drink using toasted corn flour, sugar, and anatto flour in equal preparations, with and without toasted whole soybean flours (6.25%). Through a sensory ranking trial, it is established that the drink from T. bicolor and soybeans, was preferred over other preparations with T. cacao. The pulp of T. bicolor with an interesting chemical composition, yielded an aromatic pleasant drink, and from T. bicolor, is an interesting resource for industrialization and for genetic characteristics for T. cacao improvement.

Development of apple superficial scald, soft scald, core flush, and greasiness is reduced by MCP

1-Methylcyclopropene (MCP) was used to evaluate the role of ethylene in development of apple (Malus x domestica Borkh.) physiological disorders during storage. Granny Smith, Red Chief Delicious, and Fuji apple fruit were treated with MCP at a concentration of 1 microL L(-)(1) for 12 h at 20 degrees C. For all varieties stored at 0 degrees C, ethylene production and respiration rates were reduced for several months following MCP treatment, and firmness and titratable acidity of treated fruit were higher compared to controls. Apples treated with MCP did not develop superficial scald or peel greasiness through 6 months storage plus ripening at 20 degrees C for 7 days. Core flush was not observed in MCP-treated fruit until 6 months after treatment when the incidence was still lower compared to control fruit. MCP delayed the rise in production of alpha-farnesene and reduced accumulation of its oxidation products.

Evaluation of botulinal toxin production in packaged fresh-cut cantaloupe and honeydew melons

The ability of Clostridium botulinum to produce toxin on cubed, packaged melons was investigated relative to microbial spoilage at various incubation temperatures and in different packaging systems. Freshly cut cubes (approximately 2.5 cm3) of cantaloupe and honeydew melons were surface inoculated with a 10 strain mixture of proteolytic and nonproteolytic spores of C. botulinum (10 to 15 cubes per package; approximately 100 total spores per package). To initially evaluate toxin production and spoilage in a passively modified atmosphere, melon cubes were loosely packaged in air in polyethylene pouches, sealed, and incubated at 7 or 15 degrees C for up to 21 days. At various sampling intervals, samples were tested for headspace oxygen and carbon dioxide levels, pH, presence of botulinal toxin, aerobic and anaerobic plate counts, and counts of yeasts and molds. During incubation, headspace oxygen levels decreased, headspace carbon dioxide levels increased, aerobic and anaerobic plate counts increased, and the pH remained constant or decreased slightly. Botulinal toxin was not detected in any cantaloupe samples or in honeydew samples incubated at 7 degrees C. Botulinal toxin was detected in some honeydew samples at 15 degrees C after 9 days of incubation, but the toxic honeydews were severely spoiled and considered organoleptically unacceptable. A similar second experiment was performed in which half of the melon cubes were treated with UV light to inactivate vegetative organisms before packaging, and these were incubated at 7, 15, or 27 degrees C. In this second experiment, toxin production occurred in the UV-treated samples at 15 degrees C with gross spoilage and at 27 degrees C with only marginal spoilage. These data indicate that inhibition of spoilage organisms with UV light could result in botulinal toxin formation in packaged melons before overt spoilage.

Gene encoding polygalacturonase inhibitor in apple fruit is developmentally regulated and activated by wounding and fungal infection

A cDNA encoding polygalacturonase-inhibiting protein (PGIP) from mature apple fruit has been cloned and characterized. The open reading frame encodes a polypeptide of 330 amino acids, in which 24 amino acids at the N-terminus comprise the signal peptide. Apple PGIP contains 10 imperfect leucine-rich repeat sequence motifs averaging 24 amino acids in length. In addition to the 1.3 kb PGIP transcript, the cloned cDNA also hybridized to RNA molecules with sizes of 3.2 and 5.0 kb. Genomic DNA analysis revealed that the apple PGIP probably belongs to a small family of genes. PGIP transcript levels varied in fruit collected at different maturities, suggesting the gene is developmentally regulated. Very high PGIP transcript levels were detected in decayed areas and the tissue adjacent to the inoculation sites of Penicillium expansum and Botrytis cinerea. However, no increase in the amount of PGIP transcript in tissue distant from the decayed region was observed. Wounding on fruit also induced PGIP gene expression but to a much lessser extent when compared with decayed areas. After storage at 0 degrees C for 1 month, the abundance of PGIP transcript in ripe fruit was substantially increased. The PGIP gene in immature and ripe fruit was rapidly up-regulated by fungal infections, while in stored fruit the induction was very limited and concurred with an increase of fruit susceptibility to fungal colonization. Since PGIP gene expression is regulated by fruit development and responds to wounding, fungal infection and cold storage, these observations suggest that apple PGIP may have multiple roles during fruit development and stress response.

Relationships between respiration, ethylene, and aroma production in ripening banana

Mature green bananas were treated with the ethylene antagonist 1-methylcyclopropene (1-MCP) at intervals during the 24 h period after initiation of ripening with propylene. Following 1-MCP treatment, the fruits were ripened in either air or propylene while ethylene, carbon dioxide, and volatile production and composition were monitored at regular intervals. The application of 1-MCP significantly delayed and suppressed the onset and magnitude of fruit respiration and volatile production. The 1-MCP treatments also caused a quantitative change in the composition of the aroma volatiles, resulting in a substantial increase in the concentration of alcohols and a decrease in their related esters. The results showed that ethylene has a continuing role in integrating many of the biochemical processes that take place during the ripening of bananas.

Calcium chloride sprays decrease physiological disorders following long-term cold storage of apple

Field experiments were carried out at the Horticultural Research Institute, and in five commercial apple orchards, located in southwest Finland including the Aland Islands during 1994 and 1995. The experimental cultivars were Melba, Raike, Red Atlas, Akerö, Aroma, and Lobo. The treatments were untreated control and preharvest calcium chloride (CaCl2) sprays at Ca 2.0 g/l. Fruit samples were stored for two to six months at 2-4 degrees C and 85-95% RH. The percentage of the incidence of physiological disorders of stored apples was scored. Fruit macronutrients, firmness, diameter and juice titratable acidity and percentage of soluble solids were determined. Only a few nutrient effects in the flesh of the apple cultivars were a result of CaCl2 sprayings. Preharvest CaCl2 sprays increased fruit firmness and the titratable acidity but decreased soluble solids, soluble solids/titratable acidity ratio, and the incidence of physiological storage disorders of some cultivars. When looking at the mean of all cultivars, CaCl2 sprayings increased titratable acidity and decreased soluble solids/titratable acidity ratio after four months of storage during 1995 and reduced the incidence of physiological disorders after three months of storage during 1994 and after four months of storage in 1995.

Differential expression of expansin gene family members during growth and ripening of tomato fruit

cDNA clones encoding homologues of expansins, a class of cell wall proteins involved in cell wall modification, were isolated from various stages of growing and ripening fruit of tomato (Lycopersicon esculentum). cDNAs derived from five unique expansin genes were obtained, termed tomato Exp3 to Exp7, in addition to the previously described ripening-specific tomato Exp1 (Rose et al. (1997) Proc Natl Acad Sci USA 94: 5955-5960). Deduced amino acid sequences of tomato Exp1, Exp4 and Exp6 were highly related, whereas Exp3, Exp5 and Exp7 were more divergent. Each of the five expansin genes showed a different and characteristic pattern of mRNA expression. mRNA of Exp3 was present throughout fruit growth and ripening, with highest accumulation in green expanding and maturing fruit, and lower, declining levels during ripening. Exp4 mRNA was present only in green expanding fruit, whereas Exp5 mRNA was present in expanding fruit but had highest levels in full-size maturing green fruit and declined during the early stages of ripening. mRNAs from each of these genes were also detected in leaves, stems and flowers but not in roots. Exp6 and Exp7 mRNAs were present at much lower levels than mRNAs of the other expansin genes, and were detected only in expanding or mature green fruit. The results indicate the presence of a large and complex expansin gene family in tomato, and suggest that while the expression of several expansin genes may contribute to green fruit development, only Exp1 mRNA is present at high levels during fruit ripening.

The plant PTS1 receptor: similarities and differences to its human and yeast counterparts

Two targeting signals, PTS1 and PTS2, mediate import of proteins into the peroxisomal matrix. We have cloned and sequenced the watermelon (Citrullus vulgaris) cDNA homologue to the PTS1 receptor gene (PEX5). Its gene product, CvPex5p, belongs to the family of tetratricopeptide repeat (TPR) containing proteins like the human and yeast counterparts, and exhibits 11 repeats of the sequence W-X2-(E/S)-(Y/F/Q) in its N-terminal half. According to fractionation studies the plant Pex5p is located mainly in the cytosolic fraction and therefore could function as a cycling receptor between the cytosol and glyoxysomes, as has been proposed for the Pex5p of human and some yeast peroxisomes. Transformation of the Hansenula polymorpha peroxisome deficient pex5 mutant with watermelon PEX5 resulted in restoration of peroxisome formation and the synthesis of additional membranes surrounding the peroxisomes. These structures are labeled in immunogold experiments using antibodies against the Hansenula polymorpha integral membrane protein Pex3p, confirming their peroxisomal nature. The plant Pex5p was localized by immunogold labelling mainly in the cytosol of the yeast, but also inside the newly formed peroxisomes. However, import of the PTS1 protein alcohol oxidase is only partially restored by CvPex5p.

Differential expression of genes involved in the biosynthesis and perception of ethylene during ripening of passion fruit (Passiflora edulis Sims)

An increase in the enzyme activity of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase induces the evolution of ethylene during the ripening of passion fruit. A much higher level of ethylene is produced in arils than in seeds or peels during ripening. The pattern of expression of two ACC synthase genes (PE-ACS1 and PE-ACS2), one ACC oxidase gene (PE-ACO1), and two ethylene receptor genes (PE-ETR1 and PE-ERS1) revealed that the expression of these genes is differentially regulated. Expression of PE-ACS1 and PE-ACO1 was enhanced during ripening and after ethylene treatment. However, prominent expression of PE-ACS1 was delayed compared to that of PE-ACO1. Much larger quantities of PE-ACS1 mRNA and PE-ACO1 mRNA were seen in arils than in seeds; this corresponds well with an increase in the amount of ethylene produced by the plant tissue itself. The level of PE-ACS2 mRNA was detectable in arils of the preclimacteric fruit, although it decreased during ripening. These results suggest that expression of PE-ACS1 and PE-ACO1 is required to increase the activity of ethylene biosynthetic enzymes during ripening. The level of expression of PE-ETR1 and PE-ERS1 did not significantly change over the course of ripening; however, the mRNA levels of PE-ETR1 and PE-ERS1 were much higher in arils than in seeds.

A fruit-specific putative dihydroflavonol 4-reductase gene is differentially expressed in strawberry during the ripening process

A cDNA clone encoding a putative dihydroflavonol 4-reductase gene has been isolated from a strawberry (Fragaria x ananassa cv Chandler) DNA subtractive library. Northern analysis showed that the corresponding gene is predominantly expressed in fruit, where it is first detected during elongation (green stages) and then declines and sharply increases when the initial fruit ripening events occur, at the time of initiation of anthocyanin accumulation. The transcript can be induced in unripe green fruit by removing the achenes, and this induction can be partially inhibited by treatment of de-achened fruit with naphthylacetic acid, indicating that the expression of this gene is under hormonal control. We propose that the putative dihydroflavonol 4-reductase gene in strawberry plays a main role in the biosynthesis of anthocyanin during color development at the late stages of fruit ripening; during the first stages the expression of this gene could be related to the accumulation of condensed tannins.

Polygalacturonase gene expression in ripe melon fruit supports a role for polygalacturonase in ripening-associated pectin disassembly

Ripening-associated pectin disassembly in melon is characterized by a decrease in molecular mass and an increase in the solubilization of polyuronide, modifications that in other fruit have been attributed to the activity of polygalacturonase (PG). Although it has been reported that PG activity is absent during melon fruit ripening, a mechanism for PG-independent pectin disassembly has not been positively identified. Here we provide evidence that pectin disassembly in melon (Cucumis melo) may be PG mediated. Three melon cDNA clones with significant homology to other cloned PGs were isolated from the rapidly ripening cultivar Charentais (C. melo cv Reticulatus F1 Alpha) and were expressed at high levels during fruit ripening. The expression pattern correlated temporally with an increase in pectin-degrading activity and a decrease in the molecular mass of cell wall pectins, suggesting that these genes encode functional PGs. MPG1 and MPG2 were closely related to peach fruit and tomato abscission zone PGs, and MPG3 was closely related to tomato fruit PG. MPG1, the most abundant melon PG mRNA, was expressed in Aspergillus oryzae. The culture filtrate exponentially decreased the viscosity of a pectin solution and catalyzed the linear release of reducing groups, suggesting that MPG1 encodes an endo-PG with the potential to depolymerize melon fruit cell wall pectin. Because MPG1 belongs to a group of PGs divergent from the well-characterized tomato fruit PG, this supports the involvement of a second class of PGs in fruit ripening-associated pectin disassembly.

Coordinate accumulation of antifungal proteins and hexoses constitutes a developmentally controlled defense response during fruit ripening in grape

During ripening of grape (Vitis labruscana L. cv Concord) berries, abundance of several proteins increased, coordinately with hexoses, to the extent that these became the predominant proteins in the ovary. These proteins have been identified by N-terminal amino acid-sequence analysis and/or function to be a thaumatin-like protein (grape osmotin), a lipid-transfer protein, and a basic and an acidic chitinase. The basic chitinase and grape osmotin exhibited activities against the principal grape fungal pathogens Guignardia bidwellii and Botrytis cinerea based on in vitro growth assays. The growth-inhibiting activity of the antifungal proteins was substantial at levels comparable to those that accumulate in the ripening fruit, and these activities were enhanced by as much as 70% in the presence of 1 m glucose, a physiological hexose concentration in berries. The simultaneous accumulation of the antifungal proteins and sugars during berry ripening was correlated with the characteristic development of pathogen resistance that occurs in fruits during ripening. Taken together, accumulation of these proteins, in combination with sugars, appears to constitute a novel, developmentally regulated defense mechanism against phytopathogens in the maturing fruit.

Multiple forms of polygalacturonase from banana fruits

Three multiple forms of polygalacturonase (PG) in ripe and two in unripe banana (Musa acuminata) fruits were separated by DEAE-cellulose and further purified using Sephadex G-150 chromatography. The multiple forms can be differentiated from each other on the basis of their properties. PG1 and PG3 were identified as endo-PG and PG2 as exo-PG on the basis of decrease in viscosity, increase in reducing sugar and the reaction product. PG2 and PG3 increased with the ripening of fruits. PG1, PG2 and PG3 exhibited optimum activity at pH 3.3, 3.7 and 4.3, respectively. Complete loss of PG2 and PG1 activities occurred at 60 and 70 degrees, but PG3 retained 60 and 50% activity respectively. The three forms showed a different response towards divalent metal ions. Ca2+ activated PG1 activity only. Teepol 0.1%, inhibited PG1 activity by 25%, but PG2 and PG3 activities were completely inhibited. CTAB, 0.1%, had no effect on PG1 and PG2 activities, but inhibited PG3 activity by 40%. 2-ME stimulated PG2 and PG3 activities but had no effect on PG1 activity. Gel filtration through Sephacryl indicated M(r) of 23,200, 58,000 and 130,000, respectively, for PG1, PG2 and PG3. The substrate saturation curve for PG1 and PG2 were Michaelian, while PG3 showed biphasic curve. The Km values of PG1 and PG2 were 0.22% and 0.14%, respectively.

The abundant 31-kilodalton banana pulp protein is homologous to class-III acidic chitinases

We have identified and characterized the abundant protein from the pulp of banana fruit (Musa acuminata cv. Grand Nain), and have isolated a cDNA clone encoding this protein. Comparison of the amino terminal sequence of the purified 31 kDa protein (P31) suggests that it is related to plant chitinases. Western analyses utilizing rabbit anti-P31 antiserum demonstrate that this protein is pulp-specific in banana. A full-length cDNA clone homologous to class III acidic chitinase genes has been isolated from a pulp cDNA library by differential screening. The identity of this clone as encoding P31 was verified by comparisons between the amino-terminal peptide sequence and the cDNA sequence and cross-hybridization of the translation product of the cDNA clone with P31 antiserum. Northern and western blot analyses of RNA and protein isolated from banana pulp at different stages of ripening indicate that the cDNA and protein are expressed at high levels in the pulp of unripe fruit, and that their abundance decreases as the fruit ripens. Based on its expression pattern and deduced amino acid sequence and composition, we hypothesize that the physiological role of P31 is not for plant protection, but as a storage protein in banana pulp.

Protein kinase activities in ripening mango, Mangifera indica L., fruit tissue. I: Purification and characterization of a calcium-stimulated casein kinase-I

A Ca(2+)-stimulated protein kinase (PK-I), active with dephosphorylated casein as exogenous substrate, was purified from ripening mango fruit. The purification procedure involved 30-70% ammonium sulphate fractionation and sequential anion exchange-, affinity-, hydrophobic interaction- and gel filtration chromatography. PK-I was purified ca. 40-fold with an overall yield of < 1%. The final specific activity in the presence of 0.1 mM Ca2+ was 55 nmol min-1 mg-1. Analysis of the most highly purified preparations revealed a monomeric enzyme with an M(r) of 30.9 kDa and pI of 5.1. PK-I efficiently phosphorylated casein and phosvitin, but did not phosphorylate histone II-S, histone III-S, protamine sulphate or bovine serum albumin. PK-I activity was stimulated by micromolar concentrations of Ca2+ and was dependent on millimolar Mg2+ concentrations, which could not be substituted with Mn2+. PK-I activity was stimulated by, but was not dependent on Ca2+. Calmodulin and calmodulin inhibitors did not affect PK-I activity, but heparin and cAMP acted as inhibitors. The pH and temperature optima of the enzyme under standard reaction conditions were 6.5 and 35 degrees C, respectively. The kinetic reaction mechanism of PK-I was studied by using casein as substrate. Initial velocity and product inhibition studies with ADP as product inhibitor best fit an ordered bi-bi kinetic mechanism with the Mg(2+)-ATP complex binding first to the enzyme followed by binding of the protein substrate. The K(m)ATP and K(m)casein of PK-I were 9 microM and 0.26 mg ml-1, respectively. The KiADP of PK-I was 9 microM.

Cloning and molecular characterization of a strawberry fruit ripening-related cDNA corresponding a mRNA for a low-molecular-weight heat-shock protein

We have isolated and characterized a cDNA from a strawberry fruit subtractive library that shows homology to class-I low-molecular-weight (LMW) heat-shock protein genes from other higher plants. The strawberry cDNA (clone njjs4) was a 779 bp full-length cDNA with a single open reading frame of 468 bp that is expected to encode a protein of ca. 17.4 kDa with a pI of 6.57. Southern analysis with genomic DNA showed several high-molecular-weight hybridization bands, indicating that the corresponding njjs4 gene is not present as a single copy in the genome. This strawberry gene was not expressed in roots, leaves, flowers and stolons but in fruits at specific stages of elongation and ripening. However, a differential pattern of mRNA expression was detected in the fruit tissues achenes and receptacle. The njjs4 gene expression increased in achenes accompanying the process of seed maturation whereas in the receptacle, a high mRNA expression was detected in the W2 stage, during which most of the metabolic changes leading to the fruit ripening are occurring. Our results clearly show a specific relationship of this njjs4 strawberry gene with the processes of seed maturation and fruit ripening, and strongly support that at least some of the class-I LMW heat-shock protein-like genes have a heat-stress-independent role in plant development, including fruit ripening.

A class IV chitinase is highly expressed in grape berries during ripening

Chitinase activity increased markedly at the onset of ripening in grape (Vitis vinifera L.) berries and continued to increase throughout the sugar accumulation phase of berry development. In contrast, beta-1,3-glucanase activity was not detected in grape berries at any stage of development. Two closely related chitinase cDNAs (VvChi4A and VvChi4B) were cloned from grapes. Sequence and Southern analysis indicate that these two clones may represent alleles of the same gene. The predicted proteins are acidic and have a signal peptide followed by a cysteine-rich, chitin-binding domain and a catalytic region. An analysis of their sequences indicates that they are class IV chitinase. The deduced protein sequence of VvChi4A has a high level of identity with the 32- and 28-kD chitinases present as haze proteins in wine. Expression of VvChi4 was high in berries and low in flowers but was not detected in leaves, roots, or seeds. No expression was detected in berries 2 to 8 weeks postflowering, but expression was high 12 to 16 weeks postflowering, which coincided with sugar accumulation and an increase in chitinase activity. Constitutive expression of VvChi4 appears to be fruit-specific and induced at high levels in grapes during ripening.

A cDNA clone highly expressed in ripe banana fruit shows homology to pectate lyases

A cDNA clone (Ban17), encoding a protein homologous to pectate lyase, has been isolated from a cDNA library from climacteric banana fruit by means of differential screening. Northern analysis showed that Ban17 mRNA is first detected in early climacteric fruit, reaches a steady-state maximum at the climacteric peak, and declines thereafter in overripe fruit. Accumulation of the Ban17 transcript can be induced in green banana fruit by exogenous application of ethylene. The demonstrates that expression of this gene is under hormonal control, its induction being regulated by the rapid increase in ethylene production at the onset of ripening. The deduced amino acid sequence derived from the Ban17 cDNA shares significant identity with pectate lyases from pollen and plant pathogenic bacteria of the genus Erwinia. Similarity to bacterial pectate lyases that were proven to break down the pectic substances of the plant cell wall suggest that Ban17 might play a role in the loss of mesocarp firmness during fruit ripening.

Identification and characterization of a fruit-specific, thaumatin-like protein that accumulates at very high levels in conjunction with the onset of sugar accumulation and berry softening in grapes

The protein composition of the grape (Vitis vinifera cv Muscat of Alexandria) berry was examined from flowering to ripeness by gel electrophoresis. A protein with an apparent molecular mass of 24 kD, which was one of the most abundant proteins in extracts of mature berries, was purified and identified by amino acid sequence to be a thaumatin-like protein. Combined cDNA sequence analysis and electrospray mass spectrometry revealed that this protein, VVTL1 (for V. vinifera thaumatin-like protein 1), is synthesized with a transient signal peptide as seen for apoplastic preproteins. Apart from the removal of the targeting signal and the formation of eight disulfide bonds, VVTL1 undergoes no other posttranslational modification. Southern, northern, and western analyses revealed that VVTL1 is found in the berry only and is encoded by a single gene that is expressed in conjunction with the onset of sugar accumulation and softening. The exact role of VVTL1 is unknown, but the timing of its accumulation correlates with the inability of the fungal pathogen powdery mildew (Uncinula necator) to initiate new infections of the berry. Western analysis revealed that the presence of thaumatin-like proteins in ripening fruit might be a widespread phenomenon.

Characterization of two cDNA clones for mRNAs expressed during ripening of melon (Cucumis melo L.) fruits

In vitro translation of mRNAs and polyacrylamide gel electrophoresis of proteins from melons revealed that several mRNAs increased in amount during ripening, indicating the existence of other ripening genes in addition to those cloned previously. To identify ripening-related genes we have screened a ripe melon cDNA library and isolated two novel cDNA clones (MEL2 and MEL7) encoding unidentified proteins. Southern analysis revealed that MEL2 and MEL7 are encoded by low-copy-number genes. The MEL2 cDNA clone is near full-length, corresponds to a 1600 nucleotide mRNA that accumulates during ripening and encodes a predicted protein rich in hydrophobic amino acids. The MEL7 cDNA clone is full-length, corresponds to a mRNA of 0.7 kb which accumulates during early ripening stages and is also present at low levels in other organs of the melon plant. The MEL7 predicted polypeptide is 17 kDa and shows significant homology with the major latex protein from opium-poppy. Wounding and ethylene treatment of unripe melon fruits 20 days after anthesis showed that MEL2 and MEL7 mRNAs are only induced by ethylene.

Banana sucrose-phosphate synthase gene expression during fruit ripening

A 952-base pair polymerase-chain-reaction product of sucrose-phosphate synthase (SPS) (EC 2.3.1.14) from banana (Musa acuminata cv. Nanicão) fruit was cloned and used to study expression of the enzyme during development and ripening. The deduced amino acid sequence shows that banana SPS has a high homology with the leaf, tap-root and bean enzymes from other species. Enzyme activity, and mRNA and protein levels point to an increase in SPS expression during ripening. The accumulation of sucrose was correlated to starch degradation and happened 4 d after SPS mRNA and activity had reached their maxima. These results indicate that access to substrate and transcriptional activation with increase in SPS expression might be important regulatory events of sweetening during banana fruit ripening.

Seasonal expression of a dehydrin gene in sibling deciduous and evergreen genotypes of peach (Prunus persica [L.] Batsch)

A cDNA library was created from cold-acclimated bark tissue of peach and selectively probed using an antibody directed against the lysine-rich consensus region of dehydrin proteins. Several clones were thus obtained which had a high degree of sequence similarity to other dehydrin genes. Northern analysis, using clone 5a, indicated that a 1.8 kb transcript was seasonally expressed in sibling deciduous and evergreen genotypes of peach, and also inducible by water deficit in cv. Rio Oso Gem. The evergreen and deciduous genotypes differ significantly in both their ability to cold-acclimate and in the seasonal expression of the dehydrin transcript and protein. In both genotypes, the transcript was maximally expressed during winter and undetectable in May-July. The evergreen genotype (less cold-tolerant), however, displayed transcript accumulation which lagged behind and declined sooner than in the deciduous genotype. Protein expression was similar to transcript expression, however, protein expression in the evergreen genotype lagged considerably behind transcript accumulation in the fall. This indicates that several levels of regulation of dehydrin proteins may exist during cold acclimation. A genomic clone (G10a) was isolated which contained the full-length dehydrin gene, designated ppdhn1. The peach dehydrin gene encodes 472 amino acids with a predicted size of 50,020 Da. The encoded protein (PCA60) contains nine of the lysine-rich repeats characteristic of dehydrins and two DEYGNP motifs at the amino acid terminus. A genomic blot, probed with clone 5a under stringent conditions, indicated that one or two highly homologous genes are present in peach, whereas an additional member was detected under low-stringency conditions. It is suggested that several members of the dehydrin gene family may exist in peach that vary in their relation to ppdhn1.

A rab11-like gene is developmentally regulated in ripening mango (Mangifera indica L.) fruit

A full-length cDNA clone from mango (Mangifera indica L.) fruit has homology to the rab11/YPT3 class of small GTPases. The corresponding mRNA is expressed in fruit, only during ripening. The likely involvement of this RabX protein in trafficking cell-wall modifying enzymes through the trans-Golgi network is discussed.

Stress relaxation in cherry fruit

Stress relaxation in three varieties of cherries was studied using the penetration test with a cylindrical pin, 4 mm in diameter, having a flat tip. One half of the fruit was modified by partial skinning, since experiments show that skin approximately doubles the apparent modulus of elasticity of the cherries. The skin also obscures a part of the fruit's distinctiveness, and affects the experimental results, even if a part of the fruit has been removed. A thermal activation theory with the residual part of stress was used to evaluate the stress relaxation experiments, and yielded results very similar to those previously obtained for vegetable flesh. Real consistency was observed mainly for residual stress and activation volume. It was observed that the relation between parameters Ct and log bt, and the initial relative slope of the relaxation curve provides information on fruit firmness.

Expression of ACC oxidase antisense gene inhibits ripening of cantaloupe melon fruits

The plant hormone ethylene plays a major role in the ripening of climacteric fruit. We have generated transgenic cantaloupe Charentais melons expressing an antisense ACC oxidase gene; ACC oxidase catalyzes the last step of ethylene biosynthesis. Ethylene production of transgenic fruit was < 1% of control untransformed fruit, and the ripening process was blocked both on and off the vine. The antisense phenotype could be reversed by exogenous ethylene treatment. Analysis of antisense ACC oxidase melons indicated that the ripening process includes ethylene-dependent and ethylene-independent pathways. Because the transgenic line we generated displays extended storage life and improved quality, it has a promising potential for commercial development.

Characterization of apple 18 and 31 kd allergens by microsequencing and evaluation of their content during storage and ripening

Patients with tree pollinosis frequently report allergic reactions after ingestion of apples. The severity of apple allergy has been related to the variety of apples and their degree of maturity. To generate a serum pool that is representative of various IgE-binding patterns of apple-allergic sera, serum samples from 34 patients allergic to tree pollens were screened. Only 24 serum samples reacted to the apple extract. Pooled serum was used to identify allergens in apples. An efficient and consistent extraction method for apple fruits was used to compare the immunoreactivities of extracts of different varieties (McIntosh, Red Delicious, Granny Smith, and Golden Delicious) of freshly picked and store-purchased apples. We found that Golden Delicious apples had the greatest amount of the 18 kd allergen, which has been reported to be a potent IgE-binding apple allergen. Store-purchased apples contained higher concentrations of the 18 kd allergen than freshly picked apples. In our study only 37.5% of sera reacted to the 18 kd protein, whereas 75% of the sera reacted to a 31 kd allergen. Other immunoreactive bands in apple extracts included proteins of 50, 38, 16, 14, and 13 kd. The amino-terminal amino acid sequences of the two major allergens, 18 kd and 31 kd, were determined. These sequences shared approximately 50% identity with disease resistance proteins of various plants or Bet v 1 in birch tree pollens. The appearance of various allergens was also investigated in mature apples during storage. The amount of 18 kd allergen increased significantly when apples were stored at 4 degrees C. However, under controlled atmospheric conditions in which oxygen- and carbon dioxide-induced ripening were regulated, the amount of 18 kd allergen remained unaffected. Because ripening and maturation were not associated with increases in 18 kd allergen content, the observed changes might be induced by factors related to disease resistance.

Fruitlax: management of constipation in children with disabilities

Seven children, with a variety of disabilities, who had experienced chronic constipation, participated in a study of the use of Fruitlax, a natural laxative. Using an AB single-subject design, data were collected for each child for a baseline period A (2 weeks) and for an intervention period B (minimum of 3 weeks), which included the addition of Fruitlax to the subjects' diets. Whereas each child experienced some change in bowel pattern (consistency, effort required to have a bowel movement, color, amount, frequency, and number of bowel movements per day), the particular change was different for each child. Fruitlax does appear to be a useful natural laxative for some children; however, additional research with a larger sample is required. The Glenrose Stool Consistency Tool was developed for use in this study. Further work is needed in the use of the tool by clients, their families, and health care workers.

Peroxisomal thiolase mRNA is induced during mango fruit ripening

Fruit ripening is a complex, developmentally regulated process. A series of genes have been isolated from various ripening fruits encoding enzymes mainly involved in ethylene and cell wall metabolism. In order to aid our understanding of the molecular basis of this process in a tropical fruit, a cDNA library was prepared from ripe mango (Mangifera indica L. cv. Manila). By differential screening with RNA poly(A)+ from unripe and ripe mesocarp a number of cDNAs expressing only in ripe fruit have been isolated. This paper reports the characterization of one such cDNA (pTHMF 1) from M. indica which codes for a protein highly homologous to cucumber, rat and human peroxisomal thiolase (EC 2.3.1.16), the catalyst for the last step in the beta-oxidation pathway. The cDNA for the peroxisomal mango thiolase is 1305 bp in length and codes for a protein of 432 amino acids with a predicted molecular mass of 45,532 Da. Mango thiolase is highly homologous to cucumber thiolase (80%), the only other plant thiolase whose cloning has been reported, and to rat and human thiolases (55% and 55% respectively). It is shown by northern analysis that during fruit ripening THMF 1 is up-regulated. A similar pattern of expression was detected in tomato fruit. Wounding and pathogen infection do not appear to affect THMF 1 expression. The possible involvement of thiolase in fatty acid metabolism during fruit ripening will be discussed. To our knowledge this is the first report cloning of a plant gene involved in fatty acid metabolism showing an induction during fruit ripening.

Maturation of immunoglobulin-A binding proteins in the seeds of jackfruit

The accumulation of proteins in the jackfruit seeds was monitored by extracting seeds proteins at various stages of growth. The early developing seed had several protein bands distributed over a molecular weight range of 10-67 kDa. But the mature seeds contained fewer bands with two of them being prominent at 12 and 15.4 kDa. Upon isoelectric focusing, the mature seed proteins were resolved into several bands distributed over a pH range of 4-9. While the mature seed proteins contained powerful hemagglutinating activities, these were not detected in the early developing seed. In contrast, the early developing seed had immunoglobulin A (IgA) binding activity as determined by enzyme-linked immunosorbent assay (ELISA). By Western blotting it was found that the early developing seed contained a novel 10 kDa IgA binding protein that was not present in the mature seeds.

Identification of mRNAs with enhanced expression in ripening strawberry fruit using polymerase chain reaction differential display

Fruit ripening is a complex developmental process that involves specific changes in gene expression and cellular metabolism. In climateric fruits these events are coordinated by the gaseous hormone ethylene, which is synthesized autocatalytically in the early stages of ripening. Nonclimacteric fruits do not synthesize or respond to ethylene in this manner, yet undergo many of the same physiological and biochemical changes associated with the production of a ripe fruit. To gain insight into the molecular determinants associated with nonclimacteric fruit ripening, we examined mRNA populations in ripening strawberry fruit using polymerase chain reaction (PCR) differential display. Five mRNAs with ripening-enhanced expression were identified using this approach. Three of the mRNAs appear to be fruit-specific, with little or no expression detected in vegetative tissues. Sequence analysis of cDNA clones revealed positive identities for three of the five mRNAs based on homology to known proteins. These results indicate that the differential display technique can be a useful tool to study fruit ripening and other developmental processes in plants at the RNA level.

cDNA cloning and molecular analysis of two self-incompatibility alleles from apple

Complementary DNA clones representing two alleles of the self-incompatibility (S) locus of apple (Malus x domestica Borkh.) have been isolated and characterised. One of the alleles corresponds to a 29 kDa ribonuclease (S-RNase) that was purified from pistil tissue. On northern blots, both cDNAs hybridized to a transcript that was only present in pistils and not in the other plant tissues analysed. Corresponding genomic sequences, amplified by PCR, were found to contain a single intron of 138 bp and 1100 bp respectively. Comparison of both sequences shows that the cDNAs encode mature proteins containing 65% of identical residues. Eight invariable cysteine residues, conserved regions around two histidines thought to play a role in RNA catalysis, and a number of other distinct residues are conserved between the apple S-RNases and similar proteins in the family Solanaceae. As this is the first report of sequences of S-alleles from a species belonging to a family that is not related with the Solanaceae, the structural features of S-RNases deduced from a comparison of their sequences are discussed.

Time of Aspergillus flavus infection and aflatoxin formation in ripening of figs

Figs in an orchard were inoculated with an aflatoxigenic Aspergillus flavus strain in two ways by spore injection or by dusting at three maturation stages: firm ripe, shrivelled, and dried. Fruits were individually examined for fungal development and analyzed for aflatoxin B1 (AF B1) after 2, 4, 6, 8 and 10 days. Fruit injected at the first stage showed fungal development and AF B1 contamination within two days. The toxin level increased sharply to 1 ppm after 10 days. The mean level of AF B1 (284.75 ng/g) was significantly higher than those observed in other conditions. Figs dusted at the first stage showed only a tiny fungal growth even after 10 days. AF B1 appeared after 6 days with a low frequency (35%), mean level (7.6 ng/g) and a great variation among figs (0.22-15 ng/g). Among fruits inoculated during the shrivelled fig and dried fruit stages, no fungal growth was observed and AF B1 was detected with a lower incidence in association with low mean levels (less than 1.25 ng/g). Methods of prevention of aflatoxin contamination at the critical step, the firm ripe stage, are discussed.

Cold acclimation in genetically related (sibling) deciduous and evergreen peach (Prunus persica [L.] Batsch). II. A 60-kilodalton bark protein in cold-acclimated tissues of peach is heat stable and related to the dehydrin family of proteins

In several plant species, certain cold-regulated proteins share unique properties. These proteins are (a) heat stable and (b) hydrophilic and are related to the Group 2 late embryogenesis abundant or dehydrin family of proteins. Our previous work with sibling deciduous and evergreen peach genotypes demonstrated a correlation between the level of accumulation of certain bark proteins and cold-acclimation potential of these tissues. Here we identify a 60-kD bark protein in peach (Prunus persica [L.] Batsch), PCA60 ("peach cold acclimation"), that is accumulated during cold acclimation and is heat stable. Immunological studies indicated that this protein is related to the dehydrin family of proteins and accumulates at much higher levels in the bark tissues of the deciduous genotype than in the evergreen. Amino acid composition indicated that the 60-kD protein has a compositional bias for glycine (24%), glutamic acid/glutamine (11.4%), aspartic acid/asparagine (10%), and threonine (9.6%), contains relatively low levels of aromatic amino acids (phenylalanine and tyrosine), and is rich in hydrophilic amino acids. A novel characteristic of the 60-kD cold-acclimation protein is the presence of a repeating nine-amino acid sequence. A five-amino acid stretch, which is included within this repeating motif, shares striking homology with other cold-regulated proteins and dehydrins.

Identification of dehydrin-like proteins responsive to chilling in floral buds of blueberry (Vaccinium, section Cyanococcus)

The level of three major polypeptides of 65, 60, and 14 kD increased in response to chilling unit accumulation in floral buds of a woody perennial, blueberry (Vaccinium, section Cynaococcus). The level of the polypeptides increased most dramatically within 300 h of chilling and decreased to the prechilling level with the initiation of budbreak. Cold-hardiness levels were assessed for dormant buds of Vaccinium corymbosum and Vaccinium ashei after different chilling treatments until the resumption of growth. These levels coincided with the level of the chilling-responsive polypeptides. Like some other previously described cold-induced proteins in annual plants, the level of the chilling-induced polypeptides also increased in leaves in response to cold treatment; the chilling-induced polypeptides were heat stable, resisting aggregation after incubation at 95 degrees C for 15 min. By fractionating bud proteins first by isoelectric point (pI) and then by molecular mass, the pI values of the 65- and 60-kD polypeptides were found to be 7.5 to 8.0 and the pI value of the 14-kD polypeptide was judged to be 8.5. Purification of the 65- and 60-kD polypeptides, followed by digestion with endoproteinase Lys-C and sequencing of selected fragments, revealed similarities in amino acid composition between the 65- and 60-kD polypeptides and dehydrins. Indeed, antiserum to the lysine-rich consensus sequence EKKGIMDKIKEKLPG of dehydrin proteins cross-reacted to all three of the major chilling-responsive polypeptides of blueberry, identifying these as dehydrins or dehydrin-like proteins.