Restoration of secondary metabolism in birch seedlings relieved from PAL-inhibitor

Abstract

Phenylalanine ammonia lyase (PAL) plays a key role in phenylpropanoid metabolism, catalyzing the deamination of phenylalanine (Phe) to form transcinnamic acid. Inhibitors of PAL have been used to study the physiological role of the different compounds derived from trans-cinnamic acid, and to test theories about a trade-off between growth and defence in plants. In a previous study with birch (Betula pubescens Ehrh.) seedlings, the PAL inhibitor 2-aminoindane-2-phosphonic acid monohydrate (AIP) caused an accumulation of Phe and a strong decrease in the quantity of simple phenolics, soluble condensed tannins and growth, whereas flavonol glycosides were generally not affected. The present study demonstrates restoration of secondary metabolism in the previously AIP treated birch seedlings. Our results indicate that Phe accumulated during PAL inhibition could be partly used to increase the content of the phenolic acids, flavan-3-ols and to some extent the soluble condensed tannins. Seedling growth also increased when the supply of PAL inhibitor ceased. We thereby show that the inhibition of PAL by AIP in vivo is reversible, at least for moderate AIP concentrations and the rate of restoration is dependent on the inhibitor concentration.

Inhibition of phenylpropanoid biosynthesis increases cell wall digestibility, protoplast isolation, and facilitates sustained cell division in American elm (Ulmus americana)

“…Initial studies indicated that all three PAL inhibitors were deleterious to the growth of in vitro elm plants, and insufficient leaf tissue was produced for further experiments. Similar observations have been made for birch ( Betula pubescens ) seedlings where growth was almost completely inhibited in the presence of 30 μM AIP [ 35 ]. Consequently, further experiments were conducted using a two phase suspension culture system in which leaf tissue was embedded in alginate beads suspended in liquid culture medium (Figure 2 a-f) to produce the source callus tissue.…”

“…While the approach of using AIP has dramatically increased our ability to consistently obtain large numbers of protoplasts from American elm, inhibiting the phenylpropanoid pathway with AIP is known to reduce the accumulation of biomass in a number of species [ 35 , 36 ]. In order for this technology to have practical application in developing protoplast regeneration systems in difficult woody species, it was critical to examine the viability and growth potential of the resulting protoplasts.…”

Significance of phenols in cadmium and nickel uptake

“…Although it was found that several groups of phenolic metabolites were restored to control levels several days after transfer from AIP-enriched to AIP-free medium (Nybakken et al, 2007), the present study is the first experimental evidence that this restoration occurs after prolonged exposure even in (still) AIP-enriched medium. Moreover, we also observed restoration of PAL activity even after 24 h of exposure to AIP (Kováčik et al, 2010).…”

“…This could have an effect on the changes in endogenous accumulation of metals (see below). Phenolic acids may serve as storage compounds for the biosynthesis of more complex phenolics and they were restored after the transfer from AIP-enriched to AIP-free medium (Nybakken et al, 2007). Their lower levels in the present study may therefore indicate use in the biosynthesis of other phenols, leading to only slightly changed total soluble phenols and flavonols (Tables 2 and 3; Fig.…”

Influence of media supplements on inhibition of oxidative browning and bacterial endophytes of Camellia sinensis var. sinensis

“…Though different adsorbents and antioxidants have been used in the culture media to mitigate tissue browning (necrosis), they may have significant negative effect on callus induction, Agrobacterium-mediated transformation and vir gene expression (Rana et al 2016). The effective inhibition of PAL activity and phenolic compound production using the phenylalanine structural analog 2-aminoindane-2-phosphonic acid (AIP) is documented in a variety of plant systems (Teklemariam and Blake 2004;Nybakken et al 2007;Oh et al 2009). However, effects of AIP application on tea leaf explant browning is quite uncertain because of the high levels of polyphenols in tea leaves, which suggest active phenylpropanoid pathways in tea.…”