Regio-specific prenylation of pterocarpans by a membrane-bound prenyltransferase from Psoralea corylifolia.

Prenylated pterocarpans are valuable natural products that play significant roles in plant defence and possess diverse biological activities. However, structural diversity of prenylated pterocarpans is still limited. Prenyltransferases (PTs) could catalyze the transfer of prenyl moieties to acceptor molecules and increase the structural diversity and biological activity of natural products. Up to date, only two pterocarpan PTs have been identified from plants. In this study, a new pterocarpan prenyltransferase gene, designated as PcM4DT, was identified from Psoralea corylifolia. The deduced polypeptide is predicted to be a membrane-bound protein with eight transmembrane regions. Functional characterization of recombinant PcM4DT demonstrated this enzyme could catalyze C-4 prenylation of pterocarpans, and exhibited strict substrate specificity to maackiain and 3-hydroxy-9-methoxy-pterocarpan. It also showed a strict donor specificity to DMAPP. Furthermore, removal of the putative transit peptide of PcM4DT obviously increased the catalytic activity (up to 90%). PcM4DT represents the first PT identified from the Psoralea genus.

Enhancement in furanocoumarin content and phenylalanine ammonia lyase activity in developing seedlings of Psoralea corylifolia L. in response to gamma irradiation of seeds.

Gamma irradiation of seeds is known to be an important factor in stimulating biochemical and physiological processes. The aim of the present study was to investigate phenylpropanoids and associated enzymes responsible for the production of active metabolites. Furanocoumarin content was estimated in seeds of Psoralea corylifolia L. during two successive generations (G(1) and G(2)) where as phenylalanine ammonia lyase (PAL) activity was measured in leaves at different developmental stages of P. corylifolia L. raised from seeds irradiated with variable doses of gamma rays. Maximum accumulation of psoralen and isopsoralen was observed at 15 and 20 kGy doses during G(1) and G(2) generations, respectively. Psoralen proved to be the dominating metabolite in terms of its concentration, while isopsoralen was accumulated at relatively lower concentrations in successive generations. PAL activity was induced maximally following 15 and 20 kGy in G(1) plants and was preceded by psoralen and isopsoralen accumulation which peaked at the same dose rates in both generations. These effects were transmitted and prevalent in the next generation, that is, G(2) (indirectly irradiated). These long-term changes in plant metabolomics demonstrate genomic instability induced by gamma irradiation. However, no detrimental effects were seen at any irradiation dose in seeds. Furanocoumarin concentrations were also enhanced at 15 and 20 kGy. The present study further points out the persistence of changes in the biosynthesis of coumarin derivatives in the next generation. However, accumulation of these metabolites does not lead to any lethal effects.

In vitro isolation, elicitation of psoralen in callus cultures of Psoralea corylifolia and cloning of psoralen synthase gene.

Psoralen, an important furanocoumarin occurring abundantly in seeds of Psoralea corylifolia is used as an anticancerous compound against leukemia and other cancer cell lines. Evaluation and isolation of psoralen from the calluses derived from different plant parts, viz. cotyledons, nodes, leaves and roots have been done in the present case for the first time. Amongst all, a maximum of 1934.75 µg/g f.w. of psoralen was recorded in callus derived from cotyledons, followed by 1875.50 and 1465.75 µg/g f.w. of psoralen in node and leaf derived calluses, respectively. Amount of psoralen enhanced further when cotyledonary calluses were exposed to different concentrations of organic elicitors (yeast extract, proline, inositol, casein hydrolyzate (CH), glycine, glutamine and sucrose) and precursors of psoralen (umbelliferone, cinnamic acid and NADPH). Isolation of psoralen was done using methanol as solvent through column chromatography and TLC. FT-IR and NMR further characterized and confirmed the structure of psoralen. In addition, the putative gene, psoralen synthase involved in psoralen synthesis pathway has been isolated, cloned and sequenced which comprised 1237 bp length. BLAST analysis of the gene sequence of psoralen synthase revealed that its nucleotide sequence showed 93% homology with psoralen synthase isolated from Ammi majus. This is the first report of isolation, cloning and characterization of psoralen synthase from Psoralea corylifolia.

Characterization of isoflavone synthase gene from Psoralea corylifolia: a medicinal plant.

Isoflavones are known to possess medicinal properties and implicated in plant-pathogen interaction. We have for the first time isolated and functionally characterized an isoflavones synthase (IFS) gene from a traditionally acclaimed medicinal plant Psoralea corylifolia abundantly growing in tropical and subtropical regions. The IFS catalyzes the exclusive reaction of phenylpropanoid pathway in leguminous plants to produce isoflavones. The full-length cDNA (PcIFS) of the gene comprised 1,563 bp and putatively encodes a polypeptide of 520 amino acid residues. The gene is expressed ubiquitously although at varying levels in different parts of the plant. The expression analysis suggests that the gene is responsive to methyl jasmonate, salicylic acid and wounding. Overexpression of PcIFS in non-leguminous tobacco plant led to the accumulation of isoflavones in petal tissue, suggesting it a functional gene from P. corylifolia involved in isoflavones biosynthesis.