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Guiwen W. Cheng and Patrick J. Breen

Abbreviations: DAA, days after anthesis; PAL, phenylalanine ammonia-lyase. Oregon Agricultural Experiment Station Technical Paper no. 9476. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal

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Xue Li, Chen Zang, Hang Ge, Jing Zhang, Donald Grierson, Xue-ren Yin, and Kun-song Chen

enzymes in the phenylpropanoid pathway, such as PAL, C4H, 4CL, hydroxycinnamoyl-CoA:NADPH moxidoreductase, cinnamyl alcohol dehydrogenase (CAD), etc ( Barros et al., 2015 ; Bonawitz and Chapple, 2012 ). Many of the coding genes for these enzymes have been

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Gloria Lopez-Galvez, Mikal Saltveit, and Marita Cantwel

Phenylalanine ammonia-lyase (PAL) activity in iceberg lettuce (Lactuca sativa L.) is increased in response to several kinds of stress, including wounding, exposure to ethylene, and fungal infection. Ethylene-induced PAL activity is correlated with the discoloration and shelf-life of fresh cut lettuce (Couture et al. 1993. HortScience 28:723). The objective of this research was to further characterize the kinetics of wound-induced PAL in fresh cut lettuce. Leaves of different cvs were cut into salad pieces (1.5 × 3 cm), rinsed in chlorinated water, centrifuged manually, and placed into containers at 5 or 15C through which humidified air flowed. Samples were evaluated for overall visual quality and specific types of discoloration. Midrib tissue was also finely cut (1 × 0.5 cm) for enhanced wound-induction of PAL, which was assayed spectrophotometrically. The kinetics of PAL in midrib tissue of fine cut and salad cut lettuce were similar, with maximum activities obtained within 12-16 h at 15C and within 40-60 h at 5C. Maximum PAL levels in the fine cut lettuce were 1.5-2.0 times those observed in the salad cut pieces, and similar to those induced by ethylene. The usefulness of PAL as a predictor of the storage life of fresh cut lettuce depends on simplifying and expediting the PAL assay.

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Jie Li, Scott M. Leisner, and Jonathan Frantz

-grown standard of rice ( Oryza sativa L.) straw containing 9.6 g·kg −1 (dry weight) was analyzed as a reference (L. Datnoff, personal communication). Phenylalanine ammonia lyase [PAL (EC 4.3.1.5)] enzyme assays. PAL activity was measured by the method

Open access

En-chao Liu, Li-fang Niu, Yang Yi, Li-mei Wang, You-wei Ai, Yun Zhao, Hong-xun Wang, and Ting Min

et al., 2018 ; Min et al., 2019 ). Most specific operations were similar to those conducted in the previous study. The result is the expression of gallic acid equivalent per kilogram fresh weight. Determination of PAL, PPO, and POD enzyme activities

Open access

Xiao-ting Li and Jian-ping Bao

flask, and the volume was determined using glacial acetic acid. The solution to be tested was placed in a colorimetric dish, and absorbance was measured at 280 nm to obtain the optical density value. Determination of POD, PPO, and PAL activities

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Ting Min, En-chao Liu, Jun Xie, Yang Yi, Li-mei Wang, You-wei Ai, and Hong-xun Wang

greatly enhance the shelf life and overall quality of fresh produce ( Mcdonald and Sun, 2000 ). Phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), and peroxidase (POD) are involved in the enzymatic browning of many fruits and vegetables

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Dan D. MacLean, Dennis P. Murr, Jennifer R. DeEll, and Eugene Kupferman

The ethylene antagonist 1-methylcyclopropene (1-MCP) was investigated for its potential impact on the transcription of key flavonoid biosynthetic (PAL and CHS) and ethylene perception (ERS1) genes during the postharvest storage of pear (Pyrus × communis L.). Optimally harvested red and green `d'Anjou' fruit were treated with 1 μL·L-1 1-MCP for 24 h at 0 °C to 1 °C, and subsequently placed in cold storage (0–1 °C, 90–95% RH). Fruit were removed every 21 days for 126 days, and evaluated for firmness, TSS, and ethylene and volatile production for up to 10 days (≈21 °C). Tissue samples were collected for Northern blot analysis and determination of flavonoid and chlorogenic acid content. PAL content increased during the 1-week simulated marketing period irrespective of storage duration, which coincided with an increase in respiration and ethylene content. Although it was still detectable, total PAL content was dramatically reduced by the 1-MCP treatment. CHS was abundant immediately after harvest and after removal from storage, but declined rapidly thereafter, and was not detectable after 1 week at room temperature. The 1-MCP treatment further exacerbated this decreasing trend in CHS content. ERS1 content appears to be stable throughout storage and the simulated marketing period, with levels lower in 1-MCP-treated fruit. These results suggest that 1-MCP significantly inhibits the transcription of key flavonoid and ethylene regulatory enzymes, possibly compromising the nutraceutical content of pear fruit. The increase in PAL with the concomitant decrease of CHS after removal from storage suggests a diversion of carbon from flavonoid compounds into simple phenols, such as chlorogenic acid.

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Hany M. El-Naggar, Paul E. Read, and Ayed Al-Abdallat

Phenylalanine ammonia-lyase (PAL) enzyme is the most extensively studied enzyme in the phenylpropanoid pathway. Studies on the biosynthesis of rosmarinic acid (RA) showed that the PAL enzyme catalyzes the initial step of the phenylpropanoid pathway. The increase in RA content in plant tissues in vitro coincided with the increase in PAL activity. The aim of this study was to investigate the activity of the gene responsible for the production of the PAL enzyme in the five rosemary genotypes; this will give more understanding about the accumulation of rosmarinic acid in the five rosemary genotypes. The genotypes were Majorca, Rosmarinus officinalis, Pine Scented, Madeline Hill and APR. Northern blot hybridization between the PAL gene primer and the five genotypes' cDNA showed bands at 300 bp in all the five genotypes for the PAL gene. The expression of the PAL gene was high in genotypes Majorca, Rosmarinus officinalis, and Madeline Hill, while the expression was low in genotypes Pine Scented and APR. It was expected that the genotypes having the highest PAL gene expression will produce the highest amount of RA, but the highest genotype in PAL gene expression Madeline Hill had the lowest RA production in their leaves. This could occur due to the tissue specific regulation inside plant tissues. Inside the callus tissues, where the specific tissue regulation no longer exists, the RA was produced in repetitively large amounts in genotypes with high PAL gene expression.

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Carolyn E. Lister, Jane E. Lancaster, and John R.L. Walker

Phenylalanine ammonia-lyase (PAL) activity was measured in a range of New Zealand-grown apple (Malus domestica Borkh.) cultivars at three stages of fruit development. Anthocyanin and total flavonoid levels were also measured (by HPLC) in the same fruit. There was wide variation in the level of PAL activity, anthocyanin and total flavonoid levels in different apple cultivars and at different stages of development. There was no apparent correlation between average PAL activity over the three developmental stages and final anthocyanin concentration (r = 0.34, P > 0.1), but there was significant correlation between average PAL activity over the three developmental stages and the final concentration of total flavonoids (r = 0.75, P < 0.02). An inhibitor, PAL-IS, was also assayed in the same fruit but no correlation was found between PAL-IS and final anthocyanin levels (r = -0.30, P > 0.1) or total flavonoid levels (r = 0.15, P > 0.1). These results suggest that PAL activity has an influence on total flavonoid levels in the fruit but that PAL-IS does not. Anthocyanin levels are likely controlled at a point in the flavonoid pathway other than PAL or PAL-IS.