Import, Targeting, and Processing of a Plant Polyphenol Oxidase

Sommer, A.; Ne’eman, E.; Steffens, John C.; Mayer, Alfred M.; Harel, E.

doi:10.1104/pp.105.4.1301

Cited by 138 publications

(119 citation statements)

References 41 publications

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“…Moreover, disruption of plastid PPO uptake and processing by tentoxin treatment indicated that PPO is not involved in coumarate hydroxylation [52]. Recent identification of a cytochrome p450 p-coumarate 3-hydroxylase [53] and the localization of PPO on the luminal side of thylakoid membrane [50,54] further negated this hypothesis.…”

Section: Other Possible Rolesmentioning

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: Other Possible Rolesmentioning

confidence: 99%

Functional Analysis of Polyphenol Oxidases by Antisense/Sense Technology

2007

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“…The transit sequences are rich in the hydroxylated amino acids Ser and Thr and the small, hydrophobic amino acids Ala and Val and possess a net positive charge, a11 characteristics of transit peptides (Keegstra et al, 1989). The transit peptide is known to be cleaved from other PPO proteins to give rise to the mature protein (Sommer et al, 1994). PPO was purified from the cortex of mature potato tubers and the N-terminal amino acid sequence of the 60-kD protein was determined by automated sequencing (Thygesen et al, 1994).…”

Section: Ppo Activity In Potato Tissuesmentioning

confidence: 99%

Polyphenol Oxidase in Potato (A Multigene Family That Exhibits Differential Expression Patterns)

1995

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Polyphenol oxidase (PPO) activity i n potato (Solanum tuberosum) plants was high in stolons, tubers, roots, and flowers but low in leaves and stems. PPO activity per tuber continued t o increase throughout tuber development but was highest on a fresh weight basis in developing tubers. PPO activity was greatest at the tuber exterior, including the skin and cortex tissue 1 t o 2 mm beneath the skin. Flowers had high PPO activity throughout development, particularly in the anthers and ovary. Five distinct cDNA clones encoding PPO were isolated from developing tuber RNA. POT32 was the major form expressed in tubers and was found in all parts of the tuber and at all stages of tuber development. It was also expressed in roots but not in photosynthetic tissues. POT33 was expressed in tubers but mainly i n the tissue near the skin. POT72 was detected in roots and at low levels in developing tubers. NOR333 was identical with the P2 PPO clone previously isolated from potato leaves (M.D. Hunt, N.T. Eannetta, Y. Haifeng, S.M. Newman, J.C. Plant MOI Biol 21 : 59-68) and was detected i n young leaves and in tissue near the tuber skin but was highly expressed in flowers. The results indicate that PPO is present as a small multigene family in potato and that each gene has a specific temporal and spatial pattern of expression.

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“…PPO is a copper-requiring metallo-enzyme associated with (although not found to be intrinsic to) the thylakoid membranes of the chloroplast in many plants including lettuce (Sommer et al 1994;Chazarra et al 1996;Wahler et al 2009). PPO catalyses two distinct reactions; the o-hydroxylation of monophenols to produce o-diphenols (monophenolase or cresolase activity) and the subsequent oxidation of the o-diphenols to o-quinones (diphenolase or catecholase activity), both of which require the presence of molecular oxygen (López-Galvez et al 1996;Chazarra et al 2001;Toivonen and Brummell 2008).…”

Section: Biochemistry Of Oxidative Discolourationmentioning

confidence: 99%

Oxidative discolouration in whole-head and cut lettuce: biochemical and environmental influences on a complex phenotype and potential breeding strategies to improve shelf-life

et al. 2017

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Lettuce discolouration is a key post-harvest trait. The major enzyme controlling oxidative discolouration has long been considered to be polyphenol oxidase (PPO) however, levels of PPO and subsequent development of discolouration symptoms have not always correlated. The predominance of a latent state of the enzyme in plant tissues combined with substrate activation and contemporaneous suicide inactivation mechanisms are considered as potential explanations for this phenomenon. Leaf tissue physical properties have been associated with subsequent discolouration and these may be influenced by variation in nutrient availability, especially excess nitrogen and head maturity at harvest. Mild calcium and irrigation stress has also been associated with a reduction in subsequent discolouration, although excess irrigation has been linked to increased discolouration potentially through leaf physical properties. These environmental factors, including high temperature and UV light intensities, often have impacts on levels of phenolic compounds linking the environmental responses to the biochemistry of the PPO pathway. Breeding strategies targeting the PAL and PPO pathway biochemistry and environmental response genes are discussed as a more cost-effective method of mitigating oxidative discolouration then either modified atmosphere packaging or post-harvest treatments, although current understanding of the biochemistry means that such programs are likely to be limited in nature and it is likely that they will need to be deployed alongside other methods for the foreseeable future.Keywords Lettuce Á Discolouration Á Biochemistry Á Environment Á Polyphenols Á Phenylpropanoid pathway Á Review The value of lettuceThe UK processed salad sector was valued at approximately £848 million in

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Import, Targeting, and Processing of a Plant Polyphenol Oxidase

Cited by 138 publications

References 41 publications

Functional Analysis of Polyphenol Oxidases by Antisense/Sense Technology

Functional Analysis of Polyphenol Oxidases by Antisense/Sense Technology

Polyphenol Oxidase in Potato (A Multigene Family That Exhibits Differential Expression Patterns)

Oxidative discolouration in whole-head and cut lettuce: biochemical and environmental influences on a complex phenotype and potential breeding strategies to improve shelf-life

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