Polyphenol Oxidase Enzymes in the Sap and Skin of Mango Fruit

Robinson, SP; Loveys, B. R.; Chacko, EK

doi:10.1071/pp9930099

Cited by 66 publications

(78 citation statements)

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“…Though antisense transgenic sugarcane failed to suppress PPO activity and reduce the color intensity of juice and raw sugar, further attempts to lower PPO activity may still be warranted [62]. It was shown that sapburn (browning, blackening and necrosis of the skin) in mango fruits was induced by the sap and catalyzed by PPO in the skin [63]. This problem might be alleviated by producing transgenic mango with reduced PPO activity in this tissue.…”

Section: Application Of Transgenic Plants With Modified Ppo Activitymentioning

confidence: 99%

Functional Analysis of Polyphenol Oxidases by Antisense/Sense Technology

2007

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Polyphenol oxidases (PPOs) catalyze the oxidation of phenolics to quinones, the secondary reactions of which lead to oxidative browning and postharvest losses of many fruits and vegetables. PPOs are ubiquitous in angiosperms, are inducible by both biotic and abiotic stresses, and have been implicated in several physiological processes including plant defense against pathogens and insects, the Mehler reaction, photoreduction of molecular oxygen by PSI, regulation of plastidic oxygen levels, aurone biosynthesis and the phenylpropanoid pathway. Here we review experiments in which the roles of PPO in disease and insect resistance as well as in the Mehler reaction were investigated using transgenic tomato (Lycopersicon esculentum) plants with modified PPO expression levels (suppressed PPO and overexpressing PPO). These transgenic plants showed normal growth, development and reproduction under laboratory, growth chamber and greenhouse conditions. Antisense PPO expression dramatically increased susceptibility while PPO overexpression increased resistance of tomato plants to Pseudomonas syringae. Similarly, PPO-overexpressing transgenic plants showed an increase in resistance to various insects, including common cutworm (Spodoptera litura (F.)), cotton bollworm (Helicoverpa armigera (Hübner)) and beet army worm (Spodoptera exigua (Hübner)), whereas larvae feeding on plants with suppressed PPO activity had higher larval growth rates and Molecules 2007, 12 1570 consumed more foliage. Similar increases in weight gain, foliage consumption, and survival were also observed with Colorado potato beetles (Leptinotarsa decemlineata (Say)) feeding on antisense PPO transgenic tomatoes. The putative defensive mechanisms conferred by PPO and its interaction with other defense proteins are discussed. In addition, transgenic plants with suppressed PPO exhibited more favorable water relations and decreased photoinhibition compared to nontransformed controls and transgenic plants overexpressing PPO, suggesting that PPO may have a role in the development of plant water stress and potential for photoinhibition and photooxidative damage that may be unrelated to any effects on the Mehler reaction. These results substantiate the defensive role of PPO and suggest that manipulation of PPO activity in specific tissues has the potential to provide broad-spectrum resistance simultaneously to both disease and insect pests, however, effects of PPO on postharvest quality as well as water stress physiology should also be considered. In addition to the functional analysis of tomato PPO, the application of antisense/sense technology to decipher the functions of PPO in other plant species as well as for commercial uses are discussed.

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Section: Application Of Transgenic Plants With Modified Ppo Activitymentioning

confidence: 99%

Functional Analysis of Polyphenol Oxidases by Antisense/Sense Technology

2007

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“…Wakayama (1994) also observed about 1.4 min to 2.4 min were required for 90% inhibition of the PPO from the core of six Japanese apple varieties. However, PPO from some other fruits such as banana (Chang et al, 2000), lichi (Ming et al, 1997) and mango sap (Robinson et al, 1993) offered higher resistance to thermal inactivation.…”

Section: Thermal Inactivationmentioning

confidence: 99%

CHARACTERIZATION OF POLYPHENOL OXIDASE OF SOURSOP (Annona muricataL.) FRUIT AND A COMPARATIVE STUDY OF ITS INHIBITION IN ENZYME EXTRACT AND IN PULP CARACTERIZACIÓN DE POLIFENOLOXIDASA DE FRUTOS DE GUANÁBANA (Annona muricata L.) Y ESTUDIO COMPARATIVO DE SU INHIBICIÓN EN EXTRACTOS DE ENZIMA Y EN PULPA CARACTERIZACIÓN DE POLIFENOLOXIDASA DE FROITOS DE GUANÁBANA (Annona muricata L.) E ESTUDIO COMPARATIVO DA SÚA INHIBICIÓN EN EXTRACTOS DE ENZIMA E EN PULPA

Bora

Holschuh

Vasconcelos

2004

Ciencia y Tecnologia Alimentaria

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Crude enzyme extract containing polyphenoloxidase (PPO) was obtained from ripe soursop (Annona muricata L.) fruit by extraction with 0.2 M phosphate buffer (pH 7.5) containing 0.5 M NaCl, followed by precipitation with 20, 40, 60 and 80% saturation of ammonium sulfate and dialysis against distilled water at 4ºC. The maximum PPO activity was observed in the protein fraction obtained with 60% ammonium sulphate saturation. The effect of pH (3 to 8.8), temperature (20 to 60ºC) and chemical inhibitors (ascorbic acid, EDTA and SO 2 ) at several concentrations on the PPO activity was studied. The optimum pH and temperature for PPO activity were 7.5 and 32ºC, respectively. Among chemical inhibitors, ascorbic acid and SO 2 were almost equally effective, but EDTA showed very small inhibitory effect. 61.9 and 71.5% inhibition of PPO was achieved using 0.28 mM and 0.84 mM concentrations of ascorbic acid, while for 55.4 and 70.2% inhibition 0.78 mM and 2.34 mM concentrations of SO 2 were needed. Heating the enzyme extract at 70, 80, 90 and 95ºC for 6 s reduced 15.2, 49.5, 84.8 and 95.1% PPO activity, respectively. At the natural pH of pulp (4.3), SO 2 at concentration of 3.9 mM reduced specific activity of PPO from about 60 to about 8.4 U/mg protein in partially-purified enzyme extract (PPEE), while the specific activity of 22.5 U/mg protein was retained in the pulp. Heating PPEE at 80ºC at pH 4.3 (natural pH of pulp) for about 14 s decreased specific enzyme activity from 60.0 to about 11.0 U/mg and heating during 8 min decreased to 9.0 U/mg protein. ResumenSe obtuvo un extracto crudo de enzima conteniendo polifenoloxidasas (PPO) de frutos maduros de Guanábana (Annona muricata L.) por extracción con 0,2 M tampón fosfato (pH 7,5) conteniendo 0,5 M NaCl, seguido de precipitación con 20, 40, 60 y 80% de saturación de sulfato amónico y diálisis con agua destilada a 4ºC. El máximo de actividad de PPO se observó en la fracción de proteína obtenida con 60% de saturación sulfato amónico. Se estudió el efecto del pH (3 a 8,8), temperatura (20 a 60ºC) y inhibidores químicos (ácido ascórbico, EDTA y SO 2 ) a varias concentraciones, sobre la actividad de PPO. Los óptimos de pH y temperatura para la actividad de PPO fueron 7,5 y 32ºC, respectivamente. Mientras que para los inhibidores químicos, ácido ascórbico y SO 2 fueron casi igual de efectivos, pero EDTA mostró un bajo efecto inhibidor.Se obtuvo un 61,9 y 71,5% de inhibición de PPO con 0,28 mM y 0,84 mM de concentración de ácido ascórbico, mientras que con 0,78 mM y 2,34 mM de concentración de SO 2 obtuvo un 55,4 y 70,2% de inhibición, respectivamente. Calentando el extracto enzimático a 70, 80, 90 y 95ºC durante 6 s, se redujo a 15,2, 49,5, 84,8 y 95,1% la actividad de PPO, respectivamente. Al pH natural de la pulpa (4,3), SO 2 a la concentración del extracto enzimático 3,9 mM redujo la actividad específica de PPO desde 60 a 8,4 U/mg proteína en extracto enzimático parcialmente purificado (PPEE), mientras que en la pulpa la actividad específica se retuvieron 22,5 U/mg de pr...

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“…PPO catalyses the conversion of monophenols into quinones, which has different spectral characteristics depending on the monophonols and pH (Robard et al 1999). In KP mango fruit, PPO activity was higher in the skin than in flesh and in ripe than green fruit (Robinson et al 1993). The role of PPO activity presumably becomes relatively more important in cell protection when mango fruit were ripe.…”

Section: Polyphenol Oxidasementioning

confidence: 93%

“…The role of PPO activity presumably becomes relatively more important in cell protection when mango fruit were ripe. The activity of PPO varied from cultivar to cultivar, being high in KP and low in Irwin mango fruit (Robinson et al 1993). Mango cultivar with high PPO activity on the fruit skin may be highly sensitive to LD.…”

Section: Polyphenol Oxidasementioning

confidence: 99%

“…Associated with the terpinolene reaction, enzymes in the fruit skin played a significant role in the sap burn damage (Loveys et al 1992). Robinson et al (1993) maintained that LD was caused by terpenoids from sap latex which caused vacuoles to lyse and allow phenolic compounds to come in contact with polyphenol oxidase enzymes. As a result of either of these discolouration scenarios, mango lenticels change from purple to dark brown, resulting in the typical discolouration.…”

Section: First Theory On Lenticel Damage Mechanismmentioning

confidence: 99%

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Lenticel damage on 'B74' mango fruit

Nguyen¹

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The mango (Mangifera indica L.) is a fruit crop of considerable economic and social importance.Widely renowned as the king of fruits, mangoes are produced in tropical and sub-tropical regions.In Australia, the cultivar B74 (marketed as Calypso TM ) is a recently developed hybrid cross between Kensington Pride (KP) and Sensation. Damage to lenticels, macroscopic cavities on the surface of fruit that facilitate gas exchange, limits the marketability of B74 fruit. Lenticel damage (LD) exhibits as a dark area surrounding the lenticel cavity, which reduces the visual appeal of the fruit.In the current research, the working hypothesis that high cell turgor within the lenticel cavity predisposes mango fruit to LD that is exacerbated by other stresses was tested.The characteristics and morphology of lenticels during fruit development of B74 and four other mango cultivars were comparatively examined. Lenticels on B74 fruit formed from stomata on young fruit and, more so, from cracking of the cuticle during later stages of fruit growth. B74 fruit had 2-to 7-times higher lenticel density at commercial harvest maturity than KP, Honey Gold and R2E2 fruit. Sensation fruit had a 2-fold higher lenticel density than B74. The high lenticel density on B74 fruit, as inherited from Sensation, may explain its greater susceptibility to developing commercially significant LD. Accumulation of condensed phenolics around damaged B74 lenticels was also observed macroscopically and microscopically. A larger proportion of lenticels on B74 fruit had smaller chambers at commercial harvest as compared to KP, perhaps because more lenticels formed later from cracks. There was no spatial link in terms of close proximity between sub-cuticlar epidermal resin ducts and LD. This lack of association suggests that external stressors are key LD-causing agents.The impact of tree irrigation was investigated towards discerning pre-disposing factors to LD.Withholding irrigation from B74 trees for 3 -8 weeks prior to harvest reduced soil water content and leaf stomatal conductance. However, it had no appreciable effects on either fruit water status or lenticel morphology. The severity of LD on fruit at eating ripe was not reduced by irrigation treatment, although withholding irrigation for 4 weeks prior to harvest increased LD severity on fruit at eating ripe and 7 days after eating ripe. Dipping B74 fruit after harvest into water increased LD severity by ~ 1.7 -2.0-fold after standard commercial pre-harvest irrigation. Exposure of fruit to γ-irradiation also increased LD irrespective of the irrigation treatment. Where fruit do not require irradiation, ceasing irrigation from 3 -8 weeks before harvest might represent a cost saving.iiiThe susceptibility of B74 fruit to developing LD in response to commercial packing house operations, specifically solution dipping and brushing, were investigated. Postharvest operations concomitantly increased LD severity and resulted in pigment accumulation in epidermal cells surrounding the lenticel cavity. LD sever...

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Polyphenol Oxidase Enzymes in the Sap and Skin of Mango Fruit

Cited by 66 publications

References 0 publications

Functional Analysis of Polyphenol Oxidases by Antisense/Sense Technology

Functional Analysis of Polyphenol Oxidases by Antisense/Sense Technology

Lenticel damage on 'B74' mango fruit

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