Activity of Phenylalanine Ammonia-Lyase (PAL) and Concentrations of Anthocyanins and Phenolics in Developing Strawberry Fruit

Abstract

<jats:p>Studies on regulation of production of phenolics in strawberry <jats:italic>(Fragaria X ananassa</jats:italic> Duch,) fruit were initiated by monitoring phenylalanine ammonia-lyase (PAL) activity and levels of anthocyanins, flavonoids, tannins, and other soluble phenols throughout fruit ontogeny in `Tillikum'. PAL catalyzes the first step in the biosynthesis of phenylpropanoids, which are further modified into a wide variety of phenolic compounds. Peak in PAL activity (1 mol· s<jats:sup>-1</jats:sup> = 1 kat) of 90 pkat· mg<jats:sup>-1</jats:sup> protein was detected at 5 and 27 days after anthesis (DAA), when fruit was green and nearly ripe, respectively. PAL activity was only ≈10% of peak values in the white berry stage, when. fruit growth was most rapid. The second peak in PAL activity was followed by a rapid drop, to nearly zero in red-ripe fruit at 30 DAA. Total soluble phenols reached a maximum level soon after anthesis, just before the first peak in PAL activity, then declined to a low constant value well in advance of fruit ripening. Similar changes were observed in levels of tannins and flavonoids that, at anthesis, accounted for 44% and 51% of the soluble phenols, respectively. The concentration of anthocyanin was very low throughout most of fruit development, but beginning at 23 DAA it increased from &lt;0.03 to &gt;0.53 mg·g<jats:sup>-1</jats:sup> fresh weight in 3 days. This accumulation paralleled the second rise in PAL activity. Accordingly, strawberry fruit have a developmental-dependent expression of PAL activity and accumulation of phenolic substances derived from the phenylpropanoid pathway.</jats:p>

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

“…It can be postulated that the levels of the various proteins responsible for these and other ripening-related changes differ significantly, in many cases, between immature and fully-ripe fruit. Correlations between strawberry fruit ripening and increased enzymatic activity of sucrose phosphate synthase, sucrose synthase, invertase, pectinesterase, phenylalanine ammonia-lyase, and uridine diphosphate glucose:ftavonoid O3-glucosyltransferase (UDP-GFT) have been reported [2,8,17,22,35]. Qualitative changes in m R N A populations have been detected by in vitro translation of total RNA isolated from various stages of ripening fruit [29].…”

“…Thus, there is a good correlation between RJ5 mRNA abundance and the development of color in the fruit due to anthocyanin accumulation. The enzymatic activities of phenylalanine ammonia-lyase, the first enzyme of the general phenylpropanoid pathway, and UDP-GFT, the terminal enzyme in the synthesis of pelargonidin-3-glucoside (the major anthocyanin pigment of ripe strawberry), also increase during strawberry fruit ripening [2,8,17].…”

Polyphenol metabolism of developing apple skin of a scab resistant and a susceptible apple cultivar

“…During ripening, the concentrations of these compounds decrease and in some apple cultivars, anthocyanins accumulate (Lister et al 1994). An understanding of the biosynthesis of polyphenols is important as they influence fruit quality, plant development and plant health (Cheng and Breen 1991).…”

The Effect of Irradiation on Bioactive Compounds in Plant and Plant Products

“…in the irradiated fresh fruits is due to: (i) the release of phenolic compounds from glycosidic compounds and the degradation of multimeric phenolic compounds to monomeric phenolic compounds by radiolytic products (Harrison and Were, 2007); and (ii) the increase in phenylalanine ammonia-lyase (PAL) activity during storage at low temperatures (3-10 • C, RH 80-95%) (Faragher, 1983;Oufedjikh et al, 1996;Benoit et al, 2000;Patil et al, 2004;Hussain et al, 2010). PAL is the main enzyme for the metabolism of phenols (Camm and Towers, 1973) and involves anthocyanin biosynthesis from phenylalanine (Cheng and Breen, 1991).…”