Ethylene-induced Phenylalanine Ammonia-Lyase Activity in Carrot Roots

Ethylene enhanced the activity of phenylalanine ammonialyase in carrot (Daucus carota L., var. “Nauty”) root tissue. Slight increase in enzyme activity was exhibited by root discs incubated in ethylene-free air. It was probably due to the ethylene formed within the sliced tissue. Addition of ethylene to the air stream increased phenylalanine ammonia-lyase activity and the total protein content of the discs until maximum activity was reached after 36 to 48 hours of incubation. The continuous presence of ethylene was required to maintain high level of activity. Ethylene, at a concentration of 10 microliter per liter induced higher activity than at lower or higher concentrations. CO₂ partially inhibited the ethylene-induced activity. Cycloheximide or actinomycin D effectively inhibited the ethylene-induced activity in discs that had not previously been exposed to ethylene. The results appear to support the hypothesis that the mode of action of ethylene may involve both de novo synthesis of the enzyme protein and protection or regulation of activity of the induced enzyme.     

Ethylene-enhanced Synthesis of Phenylalanine Ammonia-Lyase in Pea Seedlings

The effect of ethylene on the development of phenylalanine ammonia-lyase activity in segments excised from the epicotyl apex of pea seedling was studied. Although there was some increase in phenylalanine ammonia-lyase activity in segments not treated with ethylene, a marked increase in phenylalanine ammonia-lyase activity occurred in ethylene-treated tissues during the incubation. The induction period was estimated to be about 6 hours. The activity reached a maxmum at 30 hours and then declined. On withdrawal of ethylene, the increase was sustained for a short period and then stopped. After retreatment with ethylene, the increase was resumed. Addition of CO₂ reduced the effect of ethylene. Administration of cycloheximide or actinomycin D at an early period almost completely suppressed the increase in phenylalanine ammonia-lyase activity. However, if these inhibitors were administered at a later period, while phenylalanine ammonia-lyase activity was approaching a maximum, they not only failed to reduce but rather stimulated the activity. These results are consistent with the view that there exist both phenylalanine ammonia-lyase-synthesizing and -inactivating systems, and that the development of both systems may involve de novo synthesis of protein.     

Phenylalanine Ammonia-Lyase Activity and Anthocyanin Accumulation in Wounded Maize Mesocotyls

Activity of phenylalanine ammonia-lyase (E.C. 4.3.1.5) and anthocyanin accumulation were determined in wounded maize (Zea mays L.) mesocotyls. Mesocotyls were wounded with aluminum oxide and were placed in a 15 h light: 9 h dark photoperiod or in the dark. Extractable enzyme activity increased in response to wounding in the photoperiod but not in the dark. Anthocyanin accumulation in mesocotyls placed in the photoperiod decreased in response to wounding. The results are discussed with reference to phenylalanine ammonia-lyase activity in mesocotyl tissue wounded or inoculated with fungal pathogens.     

Promoter Activity of Phenylalanine Ammonia-Lyase Gene of Pharbitis nil in Arabidopsis

Promoter activity of phenylalanine ammonia-lyase (PAL) gene of Pharbitis nil was examined by introducing a PAL:GUS construct into Arabidopsis. GUS staining was observed in vascular bundles of hypocotyl and cotyledons, endodermal cells of the primary root, hydathodes, stigma and pollens of mature flower, abscission zones of petals and sepals and inner layer of seed coat. Light induced GUS expression in cotyledons and the upper part of hypocotyl in which anthocyanin was accumulated. Wounding also induced GUS expression. Endogenous PAL activity increased earlier than the GUS activity directed by the PAL promoter.     

Reduced Phenylalanine Ammonia-Lyase and Tyrosine Ammonia-Lyase Activities and Lignin Synthesis in Wheat Grown under Low Pressure Sodium Lamps

Wheat (Triticum aestivum L. cv Fremont) grown in hydroponic culture under 24-hour continuous irradiation at 560 to 580 micromoles per square meter per second from either metalhalide (MH), high pressure sodium (HPS), or low pressure sodium (LPS) lamps reached maturity in 70 days. Grain yields were similar under all three lamps, although LPS-grown plants lodged at maturity. Phenylalanine ammonia-lyase (PAL) and a tyrosine ammonia lyase (TAL) with lesser activity were detected in all extracts of leaf, inflorescence, and stem. Ammonia-lyase activities increased with age of the plant, and plants grown under the LPS lamp displayed PAL and TAL activities lower than wheat cultured under MH and HPS radiation. Greenhouse solar-grown wheat had the highest PAL and TAL activities. Lignin content of LPS-grown wheat was also significantly reduced from that of plants grown under MH or HPS lamps or in the greenhouse, showing a correlation with the reduced PAL and TAL activities. Ratios of far red-absorbing phytochrome to total phytochrome were similar for all three lamps, but the data do not yet warrant a conclusion about specific wavelengths missing from the LPS lamps that might have induced PAL and TAL activities in plants under the other lamps.     

植物苯丙氨酸解氨酶基因的研究进展

苯丙氨酸解氨酶(phenylalanineammonia-lyase,PAL)是连接植物初级代谢和苯丙烷类代谢、催化苯丙烷类代谢第一步反应的酶。综述植物PAL基因的研究进展,主要包括PAL基因的结构特点、表达特点和PAL基因表达的调控机制,并指出今后对PAL基因的研究方向。     

Phenylalanine Ammonia-Lyase in Sliced Sweet Potato Roots

A marked rise in the phenylalanine ammonia-lyase activity and the polyphenol synthesis was observed in sliced roots of a sweet potato. The enzyme activity was found to be localized in the root tissue adjacent to the sliced surface. In this region, the synthesis of polyphenols was much higher compared to the inner tissues. When the specific inhibitors for the protein and nucleic acid biosynthesis such as an actinomycin D and blasticidin S were added to the tissues by vacuum infiltration technique, both the development of phenylalanine ammonia-lyase activity and the synthesis of polyphenols were severely prevented. These results suggest the important role of phenylalanine ammonia-lyase in the polyphenol synthesis and de novo synthesis of the enzyme protein molecule in the sliced tissues.     

Phytochrome-mediated de Novo Synthesis of Phenylalanine Ammonia-Lyase in Cell Suspension Cultures of Parsley

After a preirradiation with ultraviolet light, phenylalanine ammonia-lyase activity in cell suspension cultures of parsley (Petroselinum hortense Hoff.) is controlled by phytochrome (red/far red photoreversibility). Isopycnic CsCl density gradient centrifugation, after labeling with ¹⁵N (90 atom%) under inductive and noninductive conditions, was used to investigate the mode of action of phytochrome in this response. After a 5hour labeling period, a buoyant density shift of 0.009 kg·l⁻¹ (0.7%) without band-broadening (indicating close to maximal labeling of the enzyme), was observed in irradiated cells. In dark-grown controls, the density shift was 0.004 kg·l⁻¹ (0.3%), accompanied by significant band-broadening, indicating turnover of about half of the enzyme pool during 5 hours. These results are taken as evidence that phytochrome controls de novo synthesis of this enzyme over a background of basal turnover.     

Phenylalanine Ammonia-Lyase Activity in Soybean Roots Extract Measured by Reverse-Phase High Performance Liquid Chromatography

Abstract: The high performance liquid chromatography (HPLC) technique was applied to measure phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) activity in soybean ( Glycine max L. Merril cv. BR16) roots. t -Cinnamate, the catalytic product of the PAL reaction was quantified at 275nm by isocratic elution with methanol: water through an ODS(M) column. Comparative experiments were carried out with 1.0 mM ferulic acid, an inducer of PAL activity. The results suggest that liquid chromatography is a rapid and sensitive method to analyze PAL activity in non-purified extract.     

Regulation of Phytoalexin Synthesis in Jackbean Callus Cultures: Stimulation of Phenylalanine Ammonia-Lyase and o-Methyltransferase

Jackbean, Canavalia ensiformis (L.), callus tissues synthesized the phytoalexin, medicarpin (3-hydroxy-9-methoxypterocarpan), when treated with spore suspensions of Pithomyces chartarum (Berk. and Curt.) M. B. Ellis, a nonpathogen of jackbean. Medicarpin was isolated from treated callus tissue and identified by its ultraviolet and mass spectra. The minimum spore concentration found to elicit medicarpin synthesis after 26 hours was 1 × 10⁵ spores/ml; levels of medicarpin in callus tissue increased linearly up to 1 × 10⁷ spores/ml, indicating that the recognition sites for presumed elicitors were not saturated. Medicarpin was first detected in callus treated with 1 × 10⁷ spores/ml, 6 to 12 hours after application, and the concentration reached a maximum at 48 hours, slowly declining thereafter to 72 hours. In callus treated with 3.15 mm HgCl₂, medicarpin concentrations were also maximum by 48 hours. Phenylalanine ammonia-lyase (EC 4.3.1.5) activity increased 2-fold in spore-treated callus after 36 hours. Isoliquiritigenin, daidzein, and genistein o-methyltransferase (EC 2.1.1.6) activities were increased 3- to 4-fold in treated callus. Caffeic acid and naringenin were more efficient substrates for o-methyltransferase activity than the other flavonoids or apigenin, but there was no increase in these o-methyltransferase activities in spore-treated callus. The phytoalexin response in this callus tissue culture system compares well with natural plant systems and should be an excellent system for investigating regulation of phytoalexin synthesis.     

Cinnamaldehyde Inhibits Phenylalanine Ammonia-Lyase and Enzymatic Browning of Cut Lettuce

Stored cut lettuce gradually turns brown on the cut section after several days of storage, because cutting induces phenylalanine ammonia-lyase (PAL) activity, the biosynthesis of polyphenol is promoted, and the polyphenols are oxidized by polyphenol oxidase. In this study, we screened for inhibitors of PAL derived from fermented broths of microbes and from foods and found that a cinnamon extract definitely inhibited PLA of cut lettuce. An active component was isolated by chromatographic procedures and was identified as trans-cinnamaldehyde. Browning of cut lettuce immersed in a solution containing trans-cinnamaldehyde was definitely repressed.     

Phenylalanine Ammonia-Lyase Genes Involved in Anthocyanin Synthesis and the Regulation of its Expression in Suspension Cultured Carrot Cells

D and is also induced rapidly and transiently by transfer of cells to fresh medium and lowering the cell density. From the carrot genomic library, four clones of PAL genes, gDcPAL1,2,3 and 4, were obtained. Analyses of nucleotide sequences revealed that only the gDcPAL3 gene is responsible for the induction of anthocyanin synthesis by 2,4-D. Several cis-elements, boxes M, P, A, L, and G, exist in the proximal promoter region of gDcPAL3. Transient expression experiments in carrot protoplasts using deletion mutants of the proximal promoter region of gDcPAL3 gene showed that boxes M and L, both of which contain core sequences of the Myb binding sites, might play an important role in gDcPAL3 promoter activity. Four myb cDNAs, Dcmyb8,10,12 and 14 were obtained from a carrot subtracted cDNA library and their structure and expression patterns were analyzed. In addition to the analysis of the proximal region of gDcPAL3 promoter, the possibility of the regulation of gene expression by genomic DNA structure and chromatin modification in metabolic differentiation is discussed. Received 10 June 2000/ Accepted in revised form 1 July 2000     

水稻、大麦幼苗胚乳中的苯丙氨酸解氨酶调节因子(PAL-R)

从萌发的水稻、大麦胚乳中,通过85％硫酸铵盐析、DE52纤维素和Sephadex G100柱层析,获得部分纯化的苯丙氨酸解氨酶调节因子(PAL—R),研究其基本性质,及体外PAL-R对PAL和PAL-I的影响,表明它们之间存在着相互作用。