Phenylalanine Ammonia-lyase mRNA Research Articles

Ultraviolet-C irradiation of wheat grains induces seedling resistance to leaf rust and powdery mildew disease

Ultraviolet-C (UV-C) irradiation of grains activated the antioxidant system and wheat seedlings’ resistance to leaf rust and powdery mildew disease under greenhouse conditions. Two wheat cultivars (Gemmeiza-12 and Sids-1) with dry and germinated grains were treated with UV-C at three exposure times (5, 10, and 15 minutes). The results indicated that the percentages of disease severity and infection type for leaf rust and powdery mildew on wheat seedlings were significantly reduced when exposed to UVC at all exposure times compared to the untreated control. The most effective treatments for both cultivars were obtained in seedlings grown from germinated grains treated with UV-C for 10 minutes. Furthermore, UV-C irradiation treatments improved plant resistance to infection by activating certain defense genes, thereby increasing the production of resistance compounds that support defense mechanisms against pathogens. Our results demonstrated that UV-C for 10 minutes can induce resistance in wheat seedlings while also increasing total chlorophyll, total phenolic compounds, phenylalanine ammonia-lyase, and peroxidase activity. In addition, phenylalanine ammonia-lyase mRNA expression levels were significantly increased in seedlings growing from germinated grains treated with UV-C for 10 minutes, as compared to both infected and uninfected controls. These findings demonstrate the potential for additional UV-C radiation treatments to enhance disease resistance.

Lipid nanoparticle delivers phenylalanine ammonia lyase mRNA to the liver leading to catabolism and clearance of phenylalanine in a phenylketonuria mouse model

Phenylketonuria (PKU) is a genetic disorder affecting around 1 in 12,000 live births (1), caused by a mutation in the phenylalanine hydroxylase (PAH) gene in the liver which facilitates the catabolism of phenylalanine (Phe). Without a functional copy of PAH, levels of Phe in the blood and tissues rise, resulting in potentially life-threatening damage to the central nervous system. (2) Treatment options for PKU are limited, and center around adherence to a strict PKU diet that suffers from poor patient compliance. There are two approved drugs available, one of which must be used in conjunction with the PKU diet and another that has serious immunological side effects. Here we demonstrate that the LUNAR® delivery technology is capable of delivering mRNA for a replacement enzyme, the bacterial phenylalanine ammonia lyase (avPAL), into the hepatic tissue of a PKU mouse, and that the enzyme is capable of metabolizing Phe and reducing serum levels of Phe for more than five days post-transfection. We further demonstrate the ability of LUNAR to deliver a plant-derived PAL protein with a similar impact on the level of serum Phe. Taken together these results demonstrate both the capability of LUNAR for the targeted delivery of PAL mRNA into hepatic tissue in vivo, replacing the defective PAH protein and successfully reducing serum Phe levels, thereby addressing the underlying cause of PKU symptoms. Secondly, that plant-based PAL proteins are a viable alternative to bacterial avPAL to reduce the immunogenic response.

Phenylalanine ammonia-lyase expression and pyranocoumarin accumulation in Angelica gigas plantlets exposed to light-emitting diodes

Angelica gigas (Dang Gui) is an important medicinal plant. In this study, we examined the accumulation of pyranocoumarin (decursin and decursinol angelate) and the expression of phenylalanine ammonia-lyase (PAL) in Korean angelica plantlet grown under different light-emitting diodes (LEDs) (red, orange, green, blue, and white). Three weeks after LED exposure (WAE), the transcript levels of phenylalanine ammonia-lyase mRNA in seedlings grown under orange LEDs were 4-, 18-, and 7-fold higher than those in seedlings grown under green, blue, and white LEDs, respectively. The decursinol angelate content was almost double than the decursin content. The highest levels of decursin (3.2 mg/g dry weight) and decursinol angelate (6 mg/g dry weight) were detected in plants grown under orange LEDs, at 2 WAE. Therefore, we suggest that orange LEDs may affect decursin and decursinol angelate accumulation. The findings of this study could help to determine an effective strategy for producing secondary metabolites in A. gigas using LED technology.

A kinetic model for flavonoid production in tea cell culture.

As one of the strategies for efficient production of a metabolite from cell cultures, a kinetic model is very useful tool to predict productivity under various culture conditions. In this study, we propose a kinetic model for flavonoid production in tea cell culture based on the cell life cycle and expression of PAL, the gene encoding phenylalanine ammonia-lyase (PAL)-the key enzyme in flavonoid biosynthesis. The flavonoid production rate was considered to be related to the amount of active PAL. Synthesis of PAL was modelled based on a general gene expression/translation mechanism, including the transcription of DNA encoding PAL into mRNA and the translation of PAL mRNA into the PAL protein. The transcription of DNA was assumed to be promoted at high light intensity and suppressed by a feedback regulatory mechanism at high flavonoid concentrations. In the model, mRNA and PAL were considered to self-decompose and to be lost by cell rupture. The model constants were estimated by fitting the experimental results obtained from tea cell cultures under various light intensities. The model accurately described the kinetic behaviors of dry and fresh cell concentrations, glucose concentration, cell viability, PAL specific activity, and flavonoid content under a wide range of light intensities. The model simulated flavonoid productivity per medium under various culture conditions. Therefore, this model will be useful to predict optimum culture conditions for maximum flavonoid productivity in cultured tea cells.

The mechanism of ethanol treatment on inhibiting lettuce enzymatic browning and microbial growth

Tissue browning greatly affects the quality and consumer acceptance of fresh-cut lettuce. Unfortunately, effective antibrowning agents that either have antimicrobial activity or compatibility are hard to find. This study investigated the effects of ethanol treatment on enzymatic browning and microbial growth on lettuce stem discs. Lettuce stem discs were treated with ethanol (200 mL/L) for 2 min, drained by salad spinner, packaged in Ziploc® bags and stored at 5 °C. Stem discs treated with ethanol exhibited better appearance and lower microbial loads than untreated samples within 14 days of storage time. Phenylalanine ammonia lyase mRNA level and enzymatic activities in the ethanol treated group were significantly suppressed, and total phenols and quinones were also reduced. In addition, ethanol treatment increased CO2 production and reduced O2 level inside the package. In comparison to heat shock, trans-cinnamaldehyde and salicylic acid immersion, ethanol treated lettuce stem discs had the least browning and best quality attributes. These results indicated that 200 mL/L ethanol treatment was the most effective approach to inhibit enzymatic browning and control microbial growth on lettuce stem discs.

Extraordinary transgressive phenotypes of hybrid tomato are influenced by epigenetics and small silencing RNAs

Hybrid organisms may fail to develop, be sterile or they may be more vigorous than either of the parents. Examples of hybrid vigour or hybrid necrosis in the F1 are often not inherited stably in subsequent generations if they are associated with overdominance. There can also be transgressive phenotypes that are inherited stably in these later generations, but the underlying mechanisms are not well understood. Here we have investigated the possibility that stable transgressive phenotypes in the progeny of crosses between cultivated tomato (Solanum lycopersicum cv. M82) and a wild relative (Solanum pennellii, accession LA716) are associated with micro or small interfering(si) RNAs. We identified loci from which these small(s)RNAs were more abundant in hybrids than in either parent and we show that accumulation of such transgressive sRNAs correlated with suppression of the corresponding target genes. In one instance this effect was associated with hypermethylation of the corresponding genomic DNA. Our results illustrate a potential role of transgressive sRNAs in plant breeding and in natural evolution with wild plants.

Cinnamaldehyde inhibits enzymatic browning of cut lettuce by repressing the induction of phenylalanine ammonia-lyase without promotion of microbial growth.

Cinnamaldehyde treatment inhibited the browning of cut lettuce during cold storage. In this study, to clarify the mechanism of inhibitory action of cinnamaldehyde against the browning and to show its microbiological merit, its effect on the browning of cut lettuce was compared to that of mild heat treatment. Both cinnamaldehyde and mild heat treatments inhibited the induction of phenylalanine ammonia-lyase (PAL) activity because of cutting. As a result, the biosynthesis of polyphenols, which are substrates of polyphenol oxidase, was inhibited. This reduction of polyphenol synthesis caused the inhibition of the browning. Cinnamaldehyde treatment repressed the induction of PAL mRNA, while mild heat treatment did not repress its induction. The increase in microbes in cut lettuce treated with cinnamaldehyde was less than that treated with mild heat after 12 days.

Activation of phenylpropanoid pathway in legume plants exposed to heavy metals. Part I. Effects of cadmium and lead on phenylalanine ammonia-lyase gene expression, enzyme activity and lignin content.

Species-specific changes in expression of phenylalanine ammonia-lyase (PAL) and lignin content were detected in roots of soybean (Glycine max L.) and lupine (Lupinus luteus L.) seedlings treated with different concentrations of cadmium (Cd(2+), 0-25 mg/l) or lead (Pb(2+), 0-350 mg/l). The stimulatory effect of both metals was observed in mRNA coding for PAL in soybean. In the case of lupine, changes of PAL mRNA level were dependent on the metal used: Cd(2+) caused a decrease, whereas Pb(2+) an increase of PAL transcript level. The activity of PAL was enhanced in both plant species at higher metal concentrations (15-25 mg/l of Cd(2+) or 150-350 mg/l of Pb(2+)); however it was not directly correlated with PAL mRNA. This suggests a transcriptional and posttranscriptional control of PAL expression under heavy metals stress. In soybean, Cd(2+) or Pb(2+) treatment increased lignin content, while in lupine the effect was opposite. The decreased lignin accumulation in lupine roots in response to heavy metals, despite an increased PAL activity, suggests that the activated phenylpropanoid pathway was involved in the synthesis of secondary metabolites other than lignin.

Pectin-derived oligosaccharides increase color and anthocyanin content in Flame Seedless grapes

Grapes grown in warm weather do not develop a desirable red color and require the use of products to enhance berry color. Pectin-derived oligosaccharides (PDOs) have been shown to have a role in various responses including plant defense, growth and development. In this work a mixture of PDOs with 3-20 degrees of polymerization was applied to Vitis vinifera cv. Flame Seedless grapes under field conditions and compared to the effects of ethephon (an ethylene-releasing compound). The effect of treatments on grape color, anthocyanin content and phenylalanine ammonia lyase (PAL) mRNA levels was evaluated. PDOs treatment increased berry color measured by the Color Index of Red Grapes (CIRG) and anthocyanin content, compared to ethephon and untreated berries (control); 1.5, 1 and 0.5 mg mL⁻¹ PDOs increased berry color by 30%, 27% and 26%, respectively, when compared to control berries. Levels of PAL mRNA accumulating in berries treated with PDOs were elevated within the first 24 h of treatment. PDOs enhanced the color and anthocyanin content of Flame Seedless grape berries possibly due by the induction of PAL mRNA expression. The results demonstrated that PDOs can be used to improve fruit quality aspects such as berry skin color.

U romyces appendiculatus Infection in BTH-Treated Bean Plants: Ultrastructural Details of a Lost Fight

The mechanisms of BTH [benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester]-induced resistance against bean rust caused by Uromyces appendiculatus have been explored in Phaseolus vulgaris by light and transmission electron microscopy, following the infection progression in plants challenged 7 days after treatment. While BTH did not affect uredospore germination and fungal penetration in the substomatal cavity, a first impairment to the colonization appeared evident about 48-96 h after inoculation, with alterations of infection hypha structure and reduction in mycelium expansion. No differences were found in this phase regarding the formation and ultrastructure of haustoria in untreated and BTH-treated plants, except for the deposition of electron-opaque material in the extrahaustorial matrix of the latter. A second and decisive impairment in fungal progression was observed at 7-10 days after inoculation when host cell penetrated, or in close contact with the fungal hyphae, were impregnated by phenolic compounds. The same was observed in fungal walls, particularly around haustoria, thus hampering the biotrophic habitus of the fungus and further mycelium spreading. This, in turn, prevented the evasion of fungal reproductive structures, the uredinia, and the appearance of visible symptoms. No particular ultrastructural alterations were observed in most of the penetrated cells, even at late stages of infection, indicating that BTH treatment does not induce host cells to respond with a hypersensitive reaction (HR). A parallel time course of the expression of phenylalanine ammonia lyase (PAL) gene, the key enzyme for the synthesis of phenylpropanoidic phytoalexins and many other phenolics, has shown that PAL mRNA is strongly and persistently transcripted in BTH-treated plants since the 6th h after treatment, though no apparent ultrastructural alterations were detectable up to some days after pathogen challenging. This indicates that BTH, at the employed concentration of 0.3 mM, directly activates the plant's own defences, thus accounting for the observed full protection against bean rust.

The effects of enhanced methionine synthesis on amino acid and anthocyanin content of potato tubers

BackgroundPotato is a staple food in the diet of the world's population and also being used as animal feed. Compared to other crops, however, potato tubers are relatively poor in the essential amino acid, methionine. Our aim was to increase the methionine content of tubers by co-expressing a gene involved in methionine synthesis with a gene encoding a methionine-rich storage protein in potato plants.ResultsIn higher plants, cystathionine γ-synthase (CgS) is the first enzyme specific to methionine biosynthesis. We attempted to increase the methionine content of tubers by expressing the deleted form of the Arabidopsis CgS (CgSΔ90), which is not regulated by methionine, in potato plants. To increase the incorporation of free methionine into a storage protein the CgSΔ90 was co-transformed with the methionine-rich 15-kD β-zein. Results demonstrated a 2- to 6-fold increase in the free methionine content and in the methionine content of the zein-containing protein fraction of the transgenic tubers. In addition, in line with higher methionine content, the amounts of soluble isoleucine and serine were also increased. However, all of the lines with high level of CgSΔ90 expression were phenotypically abnormal showing severe growth retardation, changes in leaf architecture and 40- to 60% reduction in tuber yield. Furthermore, the colour of the transgenic tubers was altered due to the reduced amounts of anthocyanin pigments. The mRNA levels of phenylalanine ammonia-lyase (PAL), the enzyme catalysing the first step of anthocyanin synthesis, were decreased.ConclusionEctopic expression of CgSΔ90 increases the methionine content of tubers, however, results in phenotypic aberrations in potato. Co-expression of the 15-kD β-zein with CgSΔ90 results in elevation of protein-bound methionine content of tubers, but can not overcome the phenotypical changes caused by CgSΔ90 and can not significantly improve the nutritional value of tubers. The level of PAL mRNA and consequently the amount of anthocyanin pigments are reduced in the CgSΔ90 transgenic tubers suggesting that methionine synthesis and production of anthocyanins is linked.

Effect of temperature and low oxygen on pericarp hardening of mangosteen fruit stored at low temperature

To investigate chilling injury of mangosteen fruit ( Garcinia mangostana L.), expressed as pericarp hardening, fruit at the red-brown and red-purple stages of maturity were stored at 6 °C (87.0% RH) and 12 °C (83.5% RH) for 15 d. Fruit stored at 6 °C had greater pericarp firmness than when stored at 12 °C and red-purple fruit were firmer than the less mature red-brown fruit. When pericarp hardening occurred, pericarp firmness and lignin contents increased while total phenolics decreased. Of the phenolic acids predominant in the hardened pericarp, p-coumaric acid declined whereas sinapic acid increased throughout the storage time. Application of low O 2 (0.25%) to red-purple fruit during storage at 6 °C (84% RH), or at room temperature (30 °C, 71.5% RH) following storage at 6 °C, did not reduce pericarp hardening and there were no significant differences in firmness, lignin and total free phenolics when compared with fruit in normal air conditions. Activities of enzymes involved in the lignin biosynthetic pathway, namely phenylalanine ammonia lyase (PAL), cinnamyl alcohol dehydrogenase (CAD) and peroxidase (POD), were determined. PAL and POD activities in pericarp tissue increased with storage time, whereas there was no change in CAD activity. Expression patterns of PAL and lignin peroxidase ( LgPOD) genes in fruit pericarp were also determined using northern blot analysis. PAL and LgPOD mRNA accumulation increased with storage time at 6 °C coincident with their enzyme activities. Low O 2 treatment had only a slight effect on PAL and LgPOD gene expression. Our results suggest that the increase in pericarp firmness of mangosteen fruit results from induction of lignin synthesis, associated with an increase in PAL and POD activity and gene expression.

Differential induction of phenylalanine ammonia-lyase gene expression in response to in vitro callus unions of Prunus spp.

Phenylalanine ammonia-lyase (PAL) is a key enzyme in the synthesis of phenolic compounds, which play a prominent role in graft union formation, including the marked effects of their accumulation in incompatibility response. The purpose of this study was to assess changes in the abundance of PAL mRNA during graft union development. Partial cDNA clones encoding the enzyme were isolated from in vitro callus tissue in the apricot (Prunus armeniaca L.) cultivar Moniqui and the plum rootstock Marianna 2624 (Prunus munsoniana x Prunus cerasifera). The deduced partial amino acid sequence showed high homology with PAL genes from other plant species. We monitored PAL expression 5, 10, 15 and 20 days after the establishment of in vitro callus unions. The levels of PAL mRNA increased 5 days after grafting in both compatible and incompatible unions. Nevertheless, significant differences were observed at the transcript level through both types of combinations from the second week. The results showed a higher level of PAL transcription in graft unions of incompatible partners, where a lack of adaptation between stock and scion takes place. The level of scion-stock compatibility was related to the PAL expression pattern. In addition, cell walls of the callus cells were not stained by phloroglucinol-HCl, indicating that the increased PAL expression did not result in the formation of lignin. However, staining with Naturstoff reagent A confirmed the highest accumulation of soluble and wall-bound phenolic compounds at the graft interface of incompatible unions.

Cloning and expression analysis of phenylalanine ammonia-lyase in relation to chilling tolerance in harvested banana fruit

Bananas are highly susceptible to chilling injury (CI) and phenylalanine ammonia-lyase (PAL), as a key enzyme involved in plant phenylpropanoid metabolism, has been associated with low temperature stress in plant tissues. However, little is known about the role of PAL (including PAL activity, gene and protein expression) in postharvest chilling tolerance of banana fruit. Two partial cDNAs sequences ( MaPAL1 and MaPAL2) with about 760 bp were cloned from banana pulp by RT-PCR. Western and northern hybridizations were used to investigate expression of PAL protein and PAL genes in fruit stored for 10 days at 7 °C (chilling temperature) and then transferred to 22 °C (room temperature). The effects of propylene (a functional ethylene analog) on their expression in relation to CI were also examined. Northern and western blot analyses revealed that mRNA transcripts of MaPAL1 and MaPAL2 and PAL protein levels in banana fruit during storage increased, reaching a peak at about day 8, and finally decreased at chilling temperature. Prior to low temperature storage, pretreatment with propylene could alleviate CI and enhance PAL activity, protein amount and mRNA transcripts of MaPAL1 and MaPAL2. Moreover, changes in PAL activity, protein amount and accumulation of MaPAL1 and MaPAL2 exhibited almost the same patterns. The results suggest that the induction of PAL in banana fruit during low temperature storage is regulated at transcriptional and translational levels, and is related to reduction in CI symptoms.

The effect of phenylethyl alcohol on PAL mRNA and enzyme activity in strawberries

Phenylethyl alcohol (PEA), a major metabolite of Pichia anomala SKM-T fermentation, is known to have mild-warm and rose-honey-like flavor. This safe material is one of the most widely used of perfume and food products. In order to investigate the effect of PEA on pigment development in strawberries, the anthocyanin content, phenylalanine ammonia lyase (PAL) activity, and PAL mRNA transcript accumulation were determined in PEA-treated strawberries ( Fragaria ananassa cv. Maehyang). The anthocyanin content of PEA-treated fruit was less than that of controls throughout the experimental period. It appeared that PEA was an irreversible competitive inhibitor ( K i 0.09 μM) of PAL. The activity of PAL in PEA-treated fruit was inhibited, and PAL mRNA accumulation was also lower on the 15th day of storage. When PEA was applied to immature (green) strawberries, PEA-treated fruit failed to develop red pigmentation and PAL mRNA transcript accumulation was inhibited.

Induction of defense responses in pea tissues by inorganic phosphate

When inorganic phosphate, a common and essential element for organisms, was applied endogenously, a rejection reaction and superoxide generation were induced in pea tissues but phytoalexin production was not. Phosphate-induced superoxide generation was sensitive to cycloheximide (CHX) and salicylhydroxamic acid (SHAM), indicating that part of the generation was dependent upon the expression of peroxidase gene(s). Peroxidases (POXs) are well known not only to scavenge hydrogen peroxide with phenolics but also to generate superoxide via NADH oxidation in the presence of p-coumaric acid and manganese ion. We cloned five pea POX cDNAs that are predicted to be located outside of the cells. The accumulation of five POX mRNAs, NTPase mRNA, and phenylalanine ammonia-lyase mRNA was measured by semiquantitative reverse transcription-polymerase chain reaction. The expression of the five POX genes was induced by a fungal elicitor. On the other hand, inorganic phosphate induced the accumulation of POX11, POX14, and POX21 mRNAs but not of POX13, POX29, and PsPAL1 mRNAs within 1–3 h after treatment of pea seedlings. In view of these findings, we discuss inorganic phosphate as a signal transmitter inducing part of the plant defense responses.

Effects of Abscisic acid and Temperature on the Anthocyanin Accumulation in Seedlings of Arabidopsis thaliana

Effects of abscisic acid(ABA) and temperature on the anthocyanin accumulation and phenylalanine ammonia lyase(PAL) activity were investigated in seedlings of Arabidopsis thaliana. In time course study, exogenous application of ABA (50-1000 μM) led to a noticeable increase in anthocyanin pigments which persisted over the following 5 days. Anthocyanins increased in concert with the chlorophyll loss. The activity of PAL, a key enzyme in the phenylpropanoid pathway, increased on exposure to ABA and reached maximum on the 4th day. This result shows that anthocyanin synthesis and PAL activity have a close physiological relationships. In the effects of temperatures (10℃, 17℃, 25℃ and 30℃) on anthocyanin accumulation and PAL activity in seedlings, a moderate-low temperatures (17℃) enhanced both anthocyanin content and PAL activity, whereas elevated temperatures (30℃) showed low levels of anthocyanin and PAL activity, suggesting a correlation between temperature-induced anthocyanin synthesis and the accumulation of PAL mRNA. Simultaneous application of ABA with temperatures induced higher anthocyanin synthesis and PAL activity in seedlings than ABA or temperature stress alone. Moderate-low temperature with ABA exposure elicited the maximal induction of anthocyanin synthesis and PAL activity. Therefore, ABA treatment significantly increased thermotolerance in A. thalinan seedlings. Ethephon and ABA showed similar mode of action in physiological effects on anthocyanin accumulation and PAL activity. Our data support that anthocyanins may be protective in preventing damage caused by environmental stresses and play an important role in the acquisition of freezing tolerance.

Isolation and characterization of a wound inducible phenylalanine ammonia‐lyase gene (LsPAL1) from Romaine lettuce leaves

Phenylalanine ammonia‐lyase (PAL) catalyses the first step controlling the rate of phenylpropanoid metabolism. Wounding is a ubiquitous stress in nature and in the harvesting and preparation of fruits and vegetables that induces an increase in PAL activity, an accumulation of phenolic compounds and subsequent tissue browning. A wound‐inducible PAL gene (LsPAL1) was isolated from Romaine lettuce by RT‐PCR. The putative protein encoded byLsPAL1is similar to predictive polypeptides sequences for other PALs. The kinetics of PAL mRNA accumulation is similar to those of induced PAL enzyme activity, with enzyme activity following mRNA accumulation by 12 h. Wound‐induced PAL transcripts accumulated in cells close to the wound sites. Tissue printing showed that PAL mRNA was associated with tissue next to the epidermis and vascular bundles. A heterologous PAL protein was expressed inE. coliand was found to show significant PAL activity.

Differential early gene expression in Phaseolus vulgaris to Mexican isolates of Colletotrichum lindemuthianum in incompatible and compatible interactions

Plants of Phaseolus vulgaris cv. Michigan Dark Red Kidney and two Mexican pathotypes of Colletotrichum lindemuthianum showing contrasting interactions, compatible with race 2 and incompatible with race 1472, were analyzed by cytological and molecular methods. All conidia germinated 12 h post-inoculation. In the incompatible interaction the conidia were fragmented, their development arrested, few appressoria were observed and no hyphae were found. In contrast, in the compatible interaction the conidia developed typical appressoria and infective hyphae. The phenylalanine ammonia-lyase mRNA increased slightly after 4 h in the compatible interaction and more strongly after 2 h in the incompatible one. cDNA fragments of expressed genes sampled 0.5–6 h post-inoculation in incompatible interaction were cloned after subtractive hybridization. Preferentially expressed cDNAs were selected by reverse northern, confirmed by respective northern blots against total RNA, and assessed by image analysis. cDNA analysis of three early differentially expressed cDNAs matched β-glucosidase, Sina (Seven in absentia) and ubiquitin-like genes. The presumptive function of these genes in the plant defense response is discussed.

Induction of Chitinase, β-1,3-Glucanase, and Phenylalanine Ammonia Lyase in Peach Fruit by UV-C Treatment

ABSTRACT Treatment of peach fruit with UV-C light caused a rapid induction of chitinase, beta-1,3-glucanase, and phenylalanine ammonia lyase (PAL) activities starting 6 h after treatment and reaching maximum levels at 96 h after treatment. By 96 h after UV-C treatment, chitinase, beta-1,3-glucanase, and PAL activities in UV-C-treated fruit were over twofold above the levels observed for the control. In nontreated control fruit, no apparent increase in chitinase and beta-1,3-glucanase activities was detected but a minor increase in PAL activity was seen. The transient increase in chitinase, beta-1,3-glucanase, and PAL activities in UV-C-treated fruit was preceded by a gradual activation of the corresponding genes. UV-C-treated fruit showed an increase in accumulation of beta-1,3-glucanase and chitinase mRNAs at 3 h after treatment, which peaked approximately 96 h posttreatment. A similar induction kinetic pattern was observed for PAL mRNA in response to UV-C treatment, except the induction started 6 h after UV-C treatment. These results show that the response of peach fruit to elicitor treatment is similar to that seen in other plant-elicitors interactions and suggests the involvement of peach biochemical defense responses in UV-C-mediated disease resistance.