Formation of auxin from tryptophan through action of polyphenols

The biology of Frankia sp. strains in the post-genome era

Progress in understanding symbiotic determinants involved in the N(2)-fixing actinorhizal plant symbioses has been slow but steady. Problems persist with studying the bacterial contributions to the symbiosis using traditional microbiological techniques. However, recent years have seen the emergence of several genomes from Frankia sp. strains and the development of techniques for manipulating plant gene expression. Approaches to understanding the bacterial side of the symbiosis have employed a range of techniques that reveal the proteomes and transcriptomes from both cultured and symbiotic frankiae. The picture beginning to emerge provides some perspective on the heterogeneity of frankial populations in both conditions. In general, frankial populations in root nodules seem to maintain a rather robust metabolism that includes nitrogen fixation and substantial biosynthesis and energy-generating pathways, along with a modified ammonium assimilation program. To date, particular bacterial genes have not been implicated in root nodule formation but some hypotheses are emerging with regard to how the plant and microorganism manage to coexist. In particular, frankiae seem to present a nonpathogenic presence to the plant that may have the effect of minimizing some plant defense responses. Future studies using high-throughput approaches will likely clarify the range of bacterial responses to symbiosis that will need to be understood in light of the more rapidly advancing work on the plant host.

Tryptophan oxidative metabolism catalyzed by geobacillus stearothermophilus: a thermophile isolated from kuwait soil contaminated with petroleum hydrocarbons

Tryptophan metabolism has been extensively studied in humans as well as in soil. Its metabolism takes place mainly through kynurenine pathway yielding hydroxylated, deaminated and many other products of physiological significance. However, tryptophan metabolism has not been studied in an isolated thermophilic bacterium. Geobacillus stearothermophilus is a local thermophile isolated from Kuwait desert soil contaminated with petroleum hydrocarbons. The bacterium grows well at 65 °C in 0.05 M phosphate buffer (pH 7), when supplied with organic compounds as a carbon source and has a good potential for transformation of steroids and related molecules. In the present study, we used tryptophan ethyl ester as a carbon source for the bacterium to study the catabolism of the amino acid at pH 5 and pH 7. In this endeavor, we have resolved twenty one transformation products of tryptophan by GC/LC and have identified them through their mass spectral fragmentation.

Extraction and partial characterization of polyphenol oxidase from banana (Musa acuminata Grande naine) roots

Polyphenol oxidase activity (PPO, EC 1.14.18.1, monophenol monooxygenase, and EC 1.10.3.2, o-diphenoloxidase) has been extensively studied in banana fruit for its role in enzymatic browning. Rapid discolouration of leaf, stem and root tissue after injury and strong pigmentation of tissue extracts indicate that PPO and phenolic compounds are ubiquitous in vegetative tissue of banana as well. They hamper biochemical and molecular studies in banana, as cumbersome adaptations of extraction protocols are required. On the other hand, PPO and phenolic compounds could be an important part of the plant's defence system against pests and diseases, including root parasitic nematodes. To facilitate future studies in this area, extraction and assay conditions for PPO from roots of banana (Musa acuminata AAA, Grande naine) were optimized. Highest enzyme activities were obtained in a 0.2 M phosphate buffer at pH 7.0 with 5% insoluble polyvinylpyrrolidone and 0.25% Triton X-100. The lowest K(m) values were obtained for dopamine and D-catechin. Monophenolase activity was shown with p-cresol. Banana root PPO was strongly inhibited by dithiothreitol and sodium metabisulfite. In root sections, oxidation of dopamine strongly co-localized with aerenchyma in the cortex. The experiments revealed indications for the involvement of root PPO and dopamine in resistance of banana against the parasitic nematode Radopholus similis.

Polyphenol oxidase and peroxidase in fruits and vegetables

Polyphenol oxidases and peroxidases are among the most studied enzymes in fruits and vegetables. Owing to the deleterious effects of discoloration and off-flavor formation induced by their actions, these enzymes have not ceased to be a matter of concern to food technologists, while their versatility as catalyst and their diversity as protein present a challenge to the biochemist. This article gives an account on the present state of knowledge in this field. The occurrence of polyphenol oxidases and peroxidases in food and food raw materials, and their role and importance in food processing are briefly outlined. Results of biochemical research including catalytic properties, substrate specificity, susceptibility towards pH and temperature, action of inhibitors, isolation, purification, and characteristics of the enzymes are given, with special emphasis on recent achievements based on high resolution separation and isoenzyme techniques. Finally, the behavior of polyphenol oxidase and peroxidase in selected major groups of fruits and vegetables is discussed. Some contradictions found in the literature are pointed out and some questions that have not been given the necessary attention by researchers so far are mentioned.

Properties of an Aminotransferase of Pea (Pisum sativum L.)

A transaminase (aminotransferase, EC 2.6.1) fraction was partially purified from shoot tips of pea (Pisum sativum L. cv. Alaska) seedlings. With alpha-ketoglutarate as co-substrate, the enzyme transaminated the following aromatic amino acids: d,l-tryptophan, d,l-tyrosine, and d,l-phenylalanine, as well as the following aliphatic amino acids: d,l-alanine, d,l-methionine, and d,l-leucine. Of other alpha-keto acids tested, pyruvate and oxalacetate were more active than alpha-ketoglutarate with d,l-tryptophan. Stoichiometric yields of indolepyruvate and glutamate were obtained with d,l-tryptophan and alpha-ketoglutarate as co-substrates. The specific activity was three times higher with d-tryptophan than with l-tryptophan.

Longitudinal distribution of growth substances in leaves of wheat (Triticum aestivum L.)

The basal fifth of the lamina, containing most of the gibberellin of young leaves, was the only part of the lamina that elongated. When the base of the lamina stopped elongating the gibberellin apparently moved up the lamina, but the leaf sheath still contained some gibberellin and continued to elongate. Old, fully elongated, leaves contained most auxin and tryptophan in the apical fifth of the lamina that was dying; young leaves contained insignificant amounts of auxin. Leaves contained two cytokinins; generally most cytokinin activity occurred in the apical fifth of leaves. Cytokinin activity was also detected in guttation drops and in ethanolic washings from leaf tips.

Auxins and cytokinins exuded during formation of roots by detached primary leaves and stems of dwarf French bean (Phaseolus vulgaris L.)

Hypocotyls of detached stems standing in culture solution produced adventitious roots sooner than did petioles of detached primary leaves. An auxin, probably indol-3-ylacetic acid, appeared in the solutions before the hypocotyls or petioles produced roots. After attaining a maximum, the amounts of auxin in the solutions decreased as fewer roots were formed. Two cytokinins were found in the culture solutions; one had a similar Rf to zeatin, the other ran more slowly on chromatograms. The amounts of cytokinin in the solutions were associated with root formation. Stems soon died unless their hypocotyls formed roots, but the primary leaves survived without roots forming provided a callus formed on the petiole. Hence adventitious roots, or callus tissues, may have produced cytokinins that replaced those produced by the original roots, found in sap exuded from the stem stumps, and were essential for survival of the stems and leaves.

Variations de quelques aclivités enzymatiques (peroxydase, catalase, AIA-oxydase) et de la teneur en polyphénols au cours de la germination de I'Orge. Influence de la kinétine

Peroxidase catalase, IAA-oxidase and polyphenol content of growing barley coleoptile. Effect of kinetin. - Kinetin strongly inhibits root and coleoptile growth of germinating barley in the dark. Treated coleoptiles become senescent before the untreated ones. Soluble proteins content, peroxidase, catalase and IAA-oxidase activity were greatly increased in treated coleoptiles while the level of polyphenols was reduced. These biochemical effects joined with the other property of kinetin to diminish α-amylase synthesis in the endosperm are discussed in relation to growth and in connection with the classic view of a cytokinin retarded senescence.

Growth Regulators in Populus tremula I. Distribution of Auxin and Growth Inhibitors

The content of acid ether-soluble auxins and inhibitors in vegetative tissues of aspen (Populus tremula L.) was determined with the Avena coleoptile straightgrowth assay. A growth promotor, tentativety identified as indol-3-yl-acetic acid, occurred in highest concentration in the growing stem parts. It was also detected in various parts of the roots. Large amounts of inhibitors (inhihitor β) were found in growing stem tissue and in upper mature stem parts. Considerably lower content of inhibitors was found in leaves, in the basal stem part and in the roots. Nonwoody growing roots and the wood of older root segments, especially, contained very smalt quantities of inhibitors. The elution volume of a part of the inhibitory activity on a Sephadex column was similar to that of abscisic acid.

Pathways of IAA Production from Tryptophan by Plants and by Tbeir Epipbytic Bacteria: a Comparison: I. IAA Formation by Sterile Pea Sections in vivo as Inftuenced by IAA Oxidase Inbibitors and by Transaminase Coenzyme

Under nonsterile conditions, IAA can be extracted from pea stem sections infiltrated with buffer, IAA, or tryptophan. This IAA has microbial origin, since its occurrence is prevented by antibiotics. All infiltrated IAA disappears in the sections. Under sterile conditions, several inhibitors of IAA oxidase prevent the complete disappearance of infiltrated IAA. Some of them permit, by preventing the disappearance of produced IAA, the formation in vivo of extractable IAA amounts from tryptophan. This IAA production is further increased by pyridoxal (phospbate), and by α-ketoglutarate.

[Occurrence and metabolism of auxin in multicellular algae of the Baltic Sea : I. On the occurrence of indole-3-acetic acid]

The algae Enteromorpha prolifera, Enteromorpha compressa, Cladophora sericea, Pylaiella litoralis, Ceramium rubrum, Nemalion multifidum and Furcellaria fastigiata contain extractable auxin. After paper chromatography in different solvents, the Triticum section-test and Avena curvature-test showed that the main activity was due to IAA. This result was supported by colour tests with indole reagents after paper and thin layer chromatography.In Ceramium rubrum, Enteromorpha prolifera and Enteromorpha compressa the low IAA level was correlated with a high content of inhibitors.Only Furcellaria fastigiata contained an auxin in the nonacidic fraction. As yet an identification was unsuccessful.Alkali-hydrolysis of the algae using N NaOH liberated large amounts of auxins. Also in this case, IAA was the main auxin. With thin layer chromatography 2 or 3 other indole derivatives could be detected.

Biosynthesis of Indoleacetic Acid from Tryptophan-C in Cell-free Extracts of Pea Shoot Tips

A 2-step, 1-dimensional thin-layer chromatographic procedure for isolating indoleacetic acid (IAA) was developed and utilized in investigations of the biosynthesis of IAA from tryptophan-(14)C in cell-free extracts of pea (Pisum sativum L.) shoot tips. Identification of a (14)C-product as IAA was by (a) co-chromatography of authentic IAA and (14)C-product on thin-layer chromatography, and (b) gas-liquid and thin-layer chromatography of authentic and presumptive IAA methyl esters. Dialysis of enzyme extracts and addition of alpha-ketoglutaric acid and pyridoxal phosphate to reaction mixtures resulted in approximately 2- to 3-fold increases in net yields of IAA over yields in non-dialyzed reaction mixtures which did not contain additives essential to a transaminase reaction of tryptophan. Addition of thiamine pyrophosphate to reaction mixtures further enhanced net biosynthesis of IAA. It is concluded that the formation of indolepyruvic acid and its subsequent decarboxylation probably are sequential reactions in the major pathway of IAA biosynthesis from tryptophan in cell-free extracts of Pisum shoot tips. Comparison of maximum net IAA biosynthesis in extracts of shoot tips of etiolated and light-grown dwarf and tall pea seedlings revealed an order, on a unit protein N basis, of: light-grown tall > light-grown dwarf > etiolated tall congruent with etiolated dwarf. It is concluded that the different rates of stem elongation among etiolated and light-grown dwarf and tall pea seedlings are correlated, in general, with differences in net IAA biosynthesis and sensitivity of the tissues to IAA.

Isolation, Purification, and Characterization of an Endogenous Root-promoting Factor Obtained from Basal Sections of Pear Hardwood Cuttings

Basal segments taken from Old Home and Bartlett pear hardwood cuttings collected at intervals during the rooting period in September were extracted with ethanol and fractionated by paper chromatography in different solvent systems. Different zones on the chromatograms were bioassayed by the mung bean rooting test, which showed high levels of promotion in Old Home basal extracts when the cuttings were obtained during the period of maximum rooting. Extracts from Bartlett cuttings, however, showed considerably less promotion activity in the bioassay but did show high levels of inhibitory activity.After the easily-rooted Old Home cuttings had been in the rooting medium for 10 days, a highly active endogenous root-promoting material was found in extracts from basal segments of cuttings having buds and which had been treated with indolebutyric acid. Similar extracts obtained from disbudded cuttings, or from cuttings with buds but not treated with indolebutyric acid, lacked this rooting-factor. Extracts obtained from all types of the difficult-to-root Bartlett cuttings also lacked this rooting-factor. The latter is believed to be produced by physiologically active Old Home buds, and is very effective in the mung bean bioassay, even at extremely low concentrations.From paper chromatographic studies, tests with spray reagents, solubility determinations, biological tests, UV spectrum analysis, and infrared spectroscopy, it is believed that this rooting factor could be a condensation product between exogenous auxin (indolebutyric acid) and a phenolic compound produced by physiologically active Old Home pear buds.

EFFECT OF (2-CHLOROETHYL) TRIMETHYLAMMONIUM CHLORIDE ON THE LEVEL OF ENDOGENOUS INDOLE COMPOUNDS IN WHEAT SEEDLINGS

A relatively simple and rapid spectrophotometric technique for quantitatively assaying indoleacetic acid (IAA) has now been used for determining the levels of free tryptophan in wheat seedlings (Trilicum vulgare L. var. Thatcher). This technique showed relatively large quantities of tryptophan, and a bioassay, lesser amounts of an auxin (probably IAA), to be present in 11-day-old dark-grown wheat seedlings. The quantities recovered were 200 to 400 μg of tryptophan and 0.30 to 0.60 μg of auxin (IAA equivalents) from 1.0 g of dried plant material.Inclusion of (2-chloroethyl)trimethylammonium chloride (CCC) in the growing medium of the wheat seedlings caused a reduction in the levels of both free tryptophan and the auxin, the magnitude of the effect increasing with increasing dose of CCC. At the highest rate used, 2500 mg per liter of CCC, tryptophan was reduced by approximately 35% and the auxin by approximately 50 to 60%. The evidence presented here indicates that the decreased level of auxin in CCC-treated plants reported by previous workers may have been due to a decreased level of tryptophan. It is therefore suggested that the effects of CCC on plants could be due to direct or indirect changes induced in the metabolism of their indole compounds.

Indoleacetic Acid Synthesis by Polyphenols in the Extraction of Pinus Phloem and Cambial Tissue

Indoleacetic acid may be formed by polyphenol oxidation of tryptophan during extraction of plant tissue with aqueous or organic solvents. Polyphenoloxidase promotes the conversion, but studies with heat-inactivated tissue indicate that the reaction can proceed without enzymes.