Effect of Ethylene on the Phenylalanine Ammonia-lyase Activity of Carrot Tissues

Ethylene stimulated the activity of l -phenylalanine ammonia-lyase (PAL) in carrot (Daucus carota L.) tissues. It is also known to induce the formation of isochlorogenic acid. However, the induction patterns were different for isochlorogenic acid and PAL activity. Ethylene action seems to be indirect, as it did not affect the PAL activity of cell-free extracts.     

Relationship of Phenylalanine Ammonia-lyase Activity to o-Hydroxycinnamic Acid Content in Melilotus alba

Phenylalanine ammonia-lyase activity was investigated in preparations representing various parts of sweetclover (Melilotus alba Desr.) plants of CuCu and cucu genotypes. In contrast to other plant parts, very young leaves and stems of CuCu plants displayed high phenylalanine ammonia-lyase activity. Initial leaf samples from CuCu plants were approximately 3 times as high in enzyme activity as leaves from cucu plants, but stems were only slightly higher in activity. Defoliation of the plants resulted in decreased enzyme activity, increased o-hydroxycinnamic acid content, and essentially no difference in enzyme activity between the genotypes. It appears that phenylalanine ammonia-lyase activity in leaves is not primarily controlled by the Cu/cu alleles and that the reaction catalyzed by this enzyme is not the limiting step in o-hydroxycinnamic acid synthesis.     

胡桐悬浮培养细胞中苯丙氨酸解氨酶活性与红厚壳素产量的关系

胡桐CR2细胞悬浮培养过程中,苯丙氨酸解氨酶(PAL)活性上升后红厚壳素产量即增加.加入真菌诱导子后,PAL活性与红厚壳素产量呈一定的正相关.以PAL抑制物降低PAL活性后,红厚壳素产量也降低;诱导物与抑制物同时加入,PAL活性与红厚壳素产量均界于诱导物处理与未处理之间.     

Gibberellic Acid-Promoted Lignification and Phenylalanine Ammonia-lyase Activity in a Dwarf Pea (Pisum sativum)

The effects of gibberellic acid on lignification in seedlings of a dwarf and a tall cultivar of pea (Pisum sativum) grown under red or white light or in the darkness, were studied. Gibberellic acid (10⁻⁶-10⁻⁴ m) promoted stem elongation in both light and dark and increased the percentage of lignin in the stems of the light-grown dwarf pea. The gibberellin had no effect on the lignin content of the tall pea although high concentrations (10⁻⁴ m) promoted growth of the tall plants. Time course studies indicated that the enhanced lignification in the gibberellin-treated dwarf plants occurred only after a lag period of several days. It was concluded that gibberellic acid-enhanced ligmification had no direct relation to gibberellic acid-promoted growth. The activity of phenylalanine ammonia-lyase (E.C. 4.3.1.5) was higher in gibberellin-treated dwarf plants grown under white or red light than in untreated dwarf plants. Gibberellic acid had no detectable effect on the activity of this enzyme when the plants were grown in darkness, just as it had no effect on lignification under dark conditions. The data suggest that in gibberellin-deficient peas the activity of phenylalanine ammonia-lyase is one of the limiting factors in lignification.     

蓝光、紫外光的受体及其对CHS表达诱导的研究

植物在进化过程中形成了对环境信号反应的能力,光是植物生长发育中的一个重要的环境信号,综述了蓝光,紫外光的受体及蓝光,紫外光对编码植物类黄酮合成中的一个重要的限速酶－苯基苯乙烯酮合酶基因CHS的诱导作用,并介绍该反应信号转导的可能组分。     

蓝光、紫外光的受体及其对CHS表达诱导的研究

植物在进化过程中形成了对环境信号反应的能力,光是植物生长发育中的一个重要的环境信号。综述了蓝光、紫外光的受体及蓝光、紫外光对编码植物类黄酮合成中的一个重要的限速酶——苯基苯乙烯酮合酶基因CHS的诱导作用,并介绍该反应信号转导的可能组分。     

Ethylene-controlled Induction of Phenylalanine Ammonia-lyase in Citrus Fruit Peel

l-Phenylalanine ammonia-lyase (PAL) activity is low in the external layers (flavedo) of intact mature grapefruit peel. Flavedo discs evince upon incubation increasing PAL activity and ethylene production. Light has no effect in enhancing PAL activity in discs. Exogenous ethylene stimulates PAL activity in the flavedo of intact mature grapefruits (half maximum stimulation at 15 ppm); such activity rapidly decreases when fruit is removed from the ethylene containing atmosphere. Carbon dioxide inhibits both ethylene production and PAL activity of discs; exogenous ethylene only partly relieves PAL inhibition. Cycloheximide inhibits both PAL activity and ethylene production by flavedo discs. The same concentration of cycloheximide also inhibits PAL activity of discs in the presence of exogenous ethylene. Protein synthesis seems therefore to be needed at both levels of ethylene evolution and enhancement of PAL activity.     

Repair of Pyrimidine Dimer Damage Induced in Yeast by Ultraviolet Light

Crude extracts from ultraviolet (UV)-irradiated yeast cells compete with UV-irradiated transforming deoxyribonucleic acid (DNA) for photoreactivating enzyme. The amount of competition is taken as a measure of the level of cyclobutyl pyrimidine dimers in the yeast DNA. A calibration of the competition using UV-irradiated calf thymus DNA indicates that an incident UV dose (1,500 ergs/mm(2)) yielding 1% survivors of wild-type cells produces between 2.5 x 10(4) to 5 x 10(4) dimers per cell. Wild-type cells irradiated in the exponential phase of growth remove or alter more than 90% of the dimers within 220 min after irradiation. Pyrimidine dimers induced in stationary-phase wild-type cells appear to remain in the DNA; however, with incubation, they become less photoreactivable in vivo, although remaining photoreactivable in vitro. In contrast, exponentially growing or stationary-phase UV-sensitive cells (rad2-17) show almost no detectable alteration of dimers. We conclude that the UV-sensitive cells lack an early step in the repair of UV-induced pyrimidine dimers.     

Induction of Phenylalanine Ammonia-lyase in Strawberry Leaf Disks: Action Spectra and Effects of Wounding, Sucrose, and Light

The increase in phenylalanine ammonia-lyase (PAL) activity in strawberry (Fragaria vesca var. WSU-1232) leaf disks required wounding, sucrose, and light and was cycloheximide-sensitive. In injured leaves and in leaf disks, the highest PAL activity was detected nearest the wounded tissues. Without wounding, no increase in activity was observed when leaves were cultured in sucrose and light.     

Stimulation of Phenylalanine Ammonia-lyase Activity and Lignification in Rice Callus Treated with Chitin,Chitosan, and Their Derivatives

By treatment of rice callus with chitin, chitosan, or their derivatives, phenyl alanine ammonia-lyase activity was stimulated up to 2.0 fold that of the control within 24 h, chitinase activity up to 3.5 fold within 48 h, and lignification up to 1.7 fold within 72 h. The elicitor activity was little affected by the chemical structure of the N-fatty acyl group (C2–C5) in chitosan.     

Properties of Phenylalanyl-tRNA Synthetase and Phenylalanine Ammonia-lyase of Pine Suspension Cultures

Phenylalanyl-tRNA synthetase and phenylalanine ammonia-lyase activities were demonstrated in partially purified extracts of pine (Pinus elliottii) suspension cultures. The optimum pH for the phenylalanyl-tRNA synthetase reaction was 7.5 and the optimum ATP and Mg²⁺ concentrations were 1.0 and 15 mM respectively. Pine, calf liver and yeast tRNA were inadequate substitutes for pea tRNA in the synthetase reaction mixtures. The optimum pH for the phenylalanine ammonia-lyase reaction was 9.0. The K_m for phenylalanine was approximately 6.6 × 10^?5M. The activity of both enzymes in the partially purified extracts was unstable on storage.     

Some Biochemical Changes Related to Starch Breakdown Induced by Blue Light Illumination and by Addition of Ammonia to Chlorella Cells

Illumination with blue light enhanced the production of ammoniaby cells of C. vulgaris 11h, while no such effect was inducedby red light illumination. Addition of ammonia caused increasesin ATP levels and decreases in Pi and ADP levels. When 5 mMNH₄Cl was added to phosphorylase and amylase isolated from thecells of C. vulgaris 11h, their activities increased about 5–15%and 40–100%, respectively. (Received June 21, 1986; Accepted December 23, 1986)     

The Suitability of a Quantitative Spectrophotometric Assay for Phenylalanine Ammonia-lyase Activity in Barley, Buckwheat, and Pea Seedlings

It has been suggested by others that the spectrophotometric assay of phenylalanine ammonia-lyase based on changes in absorbance at 290 nm may be complicated by a side reaction involving transamination from phenylalanine onto α-keto acids. This would lead to the production of phenylpyruvate which would spontaneously tautomerize and form an enol borate complex absorbing at this wavelength. We find that the inclusion of 1 ml of either 60 μm α-ketoglutarate or 500 μm phenylpyruvate in our 3-ml reaction mixtures has no significant effect on the spectrophotometric assay of phenylalanine ammonia-lyase in shoots from young seedlings of barley (Hordeum vulgare), buckwheat (Fagopyrum esculentum), or pea (Pisum sativum). Although these side reactions may be involved in preparations with very low enzyme activity, the spectrophotometric determination of phenylalanine ammonia-lyase based on changes in absorbance at 290 nm appears to be a reliable and sensitive technique in these seedlings.     

l-Phenylalanine Ammonia-lyase Activity in Robinia pseudoacacia Seedlings: I. Cyclic Phenomenon Activity during Continuous Light

Influences of light and darkness on l-phenylalanine ammonia-lyase activity of black locust (Robinia pseudoacacia) seedlings were studied. Light initiates both an increase in enzyme activity (or enzyme synthesis) and a subsequent decrease in activity. These dual influences of light create cyclic changes in l-phenylalanine ammonia lyase activity in continuous light. The cyclic changes in activity (during continued light) cannot be attributed to an endogenous rhythm and rather are related to the changes in balance between the enzyme activity and its inactivating system.     

Effects of Anoxia and Red Light on Changes Induced by Blue Light in the Membrane Potential of Pulvinar Motor Cells and Leaf Movement in Phaseolus vulgaris L.

In the dark, the membranes of the pulvinar motor cells of Phaseolusvulgaris L. were rapidly depolarized under anoxic conditionsand repolarized with re-aeration. This change in potential mayhave been due to suppression by anoxia of a respiration-dependent,electrogenic ion pump in the motor cells. When the pulvinuswas irradiated with blue light (BL) in the depolarized stateunder anoxic conditions, no marked depolarization occurred.Furthermore, a short pulse of BL did not induce transient depolarization.On continuous irradiation with red light (RL), the motor cellunder anoxic conditions showed slow recovery of the depolarizedmembrane potential. When a pulse of BL was superimposed on theRL after the recovery, transient depolarization occurred again. The leaf showed a small downward movement under anoxic conditionsbut recovered with re-aeration. Upward movement of the leafcaused by continuous application of BL to flexor cells changedto a downward movement under anoxic conditions, and re-aerationled to a return to upward movement. Unidirectional irradiationby BL of the flexor side did not cause upward movement of theleaf under anoxic conditions. However, unidirectional irradiationof RL to the flexor side caused downward movement of the leafunder anoxic conditions, which could be changed to upward movementby superimposition of irradiation with BL. The experimentalresults clearly show that BL acts mainly to inhibit (depolarize)an electrogenic component of the membrane potential in pulvinarmotor cells which is dependent on a supply of energy from respirationor photophsphorylation. (Received November 1, 1989; Accepted April 12, 1990)