J.P. Shyluk

Bio: J.P. Shyluk is an academic researcher from National Research Council. The author has contributed to research in topics: Isopimpinellin & Ruta graveolens. The author has an hindex of 1, co-authored 1 publications receiving 54 citations.

A 2-oxoglutarate-dependent dioxygenase from Ruta graveolens L. exhibits p-coumaroyl CoA 2′-hydroxylase activity (C2′H): a missing step in the synthesis of umbelliferone in plants

Abstract: Summary Coumarins are important compounds that contribute to the adaptation of plants to biotic or abiotic stresses. Among coumarins, umbelliferone occupies a pivotal position in the plant phenylpropanoid network. Previous studies indicated that umbelliferone is derived from the ortho-hydroxylation of p-coumaric acid by an unknown biochemical step to yield 2,4-dihydroxycinnamic acid, which then undergoes spontaneous lactonization. Based on a recent report of a gene encoding a 2-oxoglutarate-dependent dioxygenase from Arabidopsis thaliana that exhibited feruloyl CoA 6′-hydroxylase activity (Bourgaud et al., 2006), we combined a bioinformatic approach and a cDNA library screen to identify an orthologous ORF (Genbank accession number JF799117) from Ruta graveolens L. This ORF shares 59% amino acid identity with feruloyl CoA 6′-hydroxylase, was functionally expressed in Escherichia coli, and converted feruloyl CoA into scopoletin and p-coumaroyl CoA into umbelliferone with equal activity. Its bi-functionality was further confirmed in planta: transient expression of JF799117 in Nicotiana benthamiana yielded plants with leaves containing high levels of umbelliferone and scopoletin when compared to control plants, which contained barely detectable traces of these compounds. The expression of JF799117 was also tightly correlated to the amount of umbelliferone that was found in UV-elicited R. graveolens leaves. Therefore, JF799117 encodes a p-coumaroyl CoA 2′-hydroxylase in R. graveolens, which represents a previously uncharacterized step in the synthesis of umbelliferone in plants. Psoralen, which is an important furanocoumarin in R. graveolens, was found to be a competitive inhibitor of the enzyme, and it may exert this effect through negative feedback on the enzyme at an upstream position in the pathway.

Naturally Occurring Plant Coumarins

Abstract: Over the past 150 years, since Vogel in 1820 isolated the parent oxygen heterocycle, coumarin (1) from Coumarouna odorata = Dipteryx odorata (1), coumarins have been recognized as widely distributed plant products. The vast majority carry an oxygen substituent at C-7; consequently 7-hydroxycoumarin [umbelliferone, (2)], one of the most widely distributed coumarins, is often regarded as the parent, in a structural sense and also biogenetically, of a large number of the structurally more complex coumarins. A number of review articles on natural plant coumarins have appeared (154, 302, 344, 420, 525, 541, 548) since the last in this series (153), the most comprehensive, albeit dealing solely with coumarins of the Umbelliferae, being that of Nielsen in 1970 (419).

The effect of hormones on anthocyanin accumulation in cell cultures of Haplopappus gracilis.

Abstract: Suspension cultures of Haplopappus gracilis accumulated anthocyanin when grown in defined media with 4.5×10(-6)M 2,4-D. Transfer of cells to media with 10(-5)M kinetin or benzyladenine and no auxin or 10(-7)M NAA for 6 days resulted in increased anthocyanin concentration of the cells but the total amount of pigment was unaffected due to differences in growth rates. The cultures yielded up to 35 mg pigment per gram dry weight.Cells grown in batch culture in media with 10(-5)M kinetin and with 10(-7) M NAA or 5×10(-5)M NAA sampled and analyzed daily grew at the same rate. The concentration of anthocyanin differed, being lower in cells at 5×10(-5)M NAA. After 6 days there was a rapid increase in pigment formation, and by 14 days the concentration of anthocyanin in cells in the two media were the same.When the cells were cultured in 3.5-1 phytostats and 600 ml culture was replaced daily with 600 ml medium, anthocyanins accumulated when the NAA concentration was 10(-7)M but not at 10(-6)M. At 10(-7)M NAA the cultures remained pigmented and anthocyanin accumulation could be restored after a temporary loss of pigmentation due to an earlier, higher auxin concentration. The changes in concentration of phenylalanine ammonia-lyase did not correspond to changes in the rate of anthocyanin accumulation. The enzyme showed a maximum 4-8 h after inoculation of cells to fresh media. Cells grown on agar plates and rich in anthocyanin were observed to divide without loss of pigmentation, demonstrating that cells differentiated with respect to anthocyanin production undergo mitosis.

Stress and Secondary Metabolism in Cultured Plant Cells

Abstract: Grime1 defines “stress” in plants as the external constraints which limit the rate of dry matter production of all or part of the vegetation, e.g. shortages of water, light, mineral nutrients and suboptimal temperatures. These shortages may be an inherent characteristic of the environment, or they may be induced or intensified by the vegetation itself. The use of the word “stress” to describe an external constraint on dry matter production differs from that of many plant physiologists however, who have used the word to describe the physiological state of the plant. Grime’s definition could be applied to cultured plant cells; stress in this case would be any type of constraint which reduces the dry matter of the cultures. This otherwise excellent and precise definition is not very useful, however, to phytochemists who are generally not interested in dry matter production. We will define stress as the external constraints on cultured cells which limit the normal production of secondary metabolites. Let us call this phytochemical stress to be absolutely specific.