Biomedical subjects
Publications and source records attributed to J Schripsema.
From the aerial parts of Hypericum polyanthemum Klotzsch ex Reichardt (Guttiferae), three chromenes, 6-isobutyryl-5,7-dimethoxy-2,2-dimethyl-benzopyran; 7-hydroxy-6-isobutyryl-5-methoxy-2,2-dimethyl-benzopyran and 5-hydroxy-6-isobutyryl-7-methoxy-2,2-dimethyl-benzopyran were isolated. Their structures were determined by NMR spectroscopic analyses.
The distribution of iridoids among the tribes of Bignoniaceae is shown. In the present work, 18 species from the tribes Bignonieae and Tecomeae as well as one from Eccremocarpeae have been investigated. These data combined with those obtained through a literature review were analysed and showed that iridoids occur predominantly in the tribe Tecomeae. In this tribe, a chemical distintion between the genera Tabebuia and Tecoma was observed: The iridoids in Tabebuia are decarboxylated whereas in Tecoma they are C-4 formylated. The species from Bignonieae are poorly investigated and only few reports have been published, however, the iridoids found are mainly C-4 carboxylated. The only exception, Dolichandra cynanchoides (=Macfadyena cynanchoides), with decarboxylated iridoids, is also morphologically abnormal in Bignonieae.
Small bacteriocin was isolated from the culture broth of the gram-negative bacterium Rhizobium leguminosarum, which forms symbiotic nitrogen-fixing root nodules on a number of leguminous plants. The structure of the molecule was elucidated by spectroscopic methods and identified as N-(3R-hydroxy-7-cis-tetradecanoyl)-L-homoserine lactone. The absolute configuration of both asymmetric carbon atoms in the molecule was determined by the use of the chiral solvating agents S-(+)- and R-(-)-2,2,2-trifluoro-1-(9-anthryl)-ethanol. small bacteriocin is structurally related to the quorum sensing co-transcription factors for genes from other bacteria such as Vibrio fischeri, Pseudomonas aeruginosa, Erwinia carotovora, and Agrobacterium tumefaciens which are involved in animal-microbe or plant-microbe interactions. The mechanism of regulation of such interactions by this kind of co-transcription factors is still unknown in R. leguminosarum.
Nodulation (root nodule formation) in legume roots is initiated by the induction of cell divisions and formation of root nodule primordia in the plant root cortex, usually in front of the protoxylem ridges of the central root cylinder. We isolated a factor from the central cylinder (stele) of pea roots which enhances hormone-induced cell proliferation in root cortex explants at positions similar to those of nodule primordia. The factor was identified as uridine. Uridine may act as a morphogen in plant roots at picomolar concentrations.
Inoculation of Vicia sativa subsp. nigra (V. sativa) roots with Rhizobium leguminosarum biovar. viciae (R.l. viciae) bacteria substantially increases the ability of V. sativa to induce rhizobial nodulation (nod) genes. This increase is caused by the additional release of flavanones and chalcones which all induce the nod genes of R.l. viciae (K. Recourt et al., Plant Mol Biol 16: 841-852). In this paper, we describe the analyses of the flavonoids present in roots of V. sativa. Independent of inoculation with R.l. viciae, these roots contain four 3-O-glycosides of the flavonol kaempferol. These flavonoids appeared not capable of inducing the nod genes of R.l. viciae but instead are moderately active in inhibiting the activated state of those nod genes. Roots of 7-day-old V. sativa seedlings did not show any kaempferol-glycosidase activity consistent with the observation that kaempferol is not released upon inoculation with R.l. viciae. It is therefore most likely that inoculation with infective (nodulating) R.l. viciae bacteria results in de novo flavonoid biosynthesis and not in liberation of flavonoids from a pre-existing pool.
Three strains derived from one cell line of a suspension culture of TABERNAEMONTANA DIVARICATA were obtained by subculturing on three different media: (i) Strain A: normal MS-medium (1), (ii) Strain S: medium in which the carbon source was starch instead of sucrose, and (iii) Strain N: medium in which the ammonium/nitrate ratio was changed from 1: 2 to 1:1. The alkaloid contents of all three strains were compared at each subculture for nearly one year. Strain N showed after its initiation a gradually increasing alkaloid production up to levels of about 500 microg/gDW. Strain A (on the original medium) showed a stable, but low alkaloid production (+/- 20 microg/gDW) while strain S turned into a non-producing line. The dissimilation curves, morphology, intracellular carbohydrates, and free amino acid pools of all three strains were determined. Strain N showed the highest biomass, the least dissimilation, most plastids, most intracellular carbohydrates, and high levels of arginine and glutamine, while strain S showed the lowest biomass, most dissimilation, no plastids, little intracellular carbohydrates, and high levels of arginine, phenylalanine, and tyrosine. The observed differences are discussed and evidence is provided that the differences are not caused by genetic instability.
Flavonoids released by roots of Vicia sativa subsp. nigra (V. sativa) activate nodulation genes of the homologous bacterium Rhizobium leguminosarum biovar viciae (R. l. viciae). Inoculation of V. sativa roots with infective R. l. viciae bacteria largely increases the nod gene-inducing ability of V. sativa root exudate (A.A.N. van Brussel et al., J Bact 172: 5394-5401). The present study showed that, in contrast to sterile roots and roots inoculated with R. l. viciae cured of its Sym plasmid, roots inoculated with R. l. viciae harboring its Sym plasmid released additional nod gene-inducing flavonoids. Using 1H-NMR, the structures of the major inducers released by inoculated roots, 6 flavanones and 2 chalcones, were elucidated. Roots extracts of (un)inoculated V. sativa contain 4 major non-inducing, most likely glycosylated, flavonoids. Therefore, the released flavonoids may either derive from the root flavonoids or inoculation with R. l. viciae activates de novo flavonoid biosynthesis.
Alkaloid production in TABERNAEMONTANA PANDACAQUI cultures is dependent on the degree of differentiation. At high levels of production the major alkaloid found was 3 S-hydroxyvoacangine. This alkaloid has not previously been isolated from any plant. Micropropagation of T. PANDACAQUI was quick and highly efficient.
The 6-methoxyflavones hispidulin and eupafolin have been identified for the first time from the aerial parts of Eupatorium cannabinum L. The presence of the previously known flavonol glycosides astragalin, kaempferol-3-rutinoside, hyperoside, isoquercitrin and rutin could be confirmed. Hispidulin, eupafolin and rutin were screened for cytotoxicity in vitro.
Root exudate of Vicia sativa contains 7 inducers for the nodA promoter of Rhizobium leguminosarum biovar viciae. Six of these inducers are flavanones. One inducer was identified as 3,5,7,3'-tetrahydroxy-4'-methoxyflavanone, and a second inducer most likely is 7,3'-dihydroxy-4'-methoxyflavanone. The inducing activity of these compounds and the other inducers depends on the nodD gene present in the test strains, which originated either from R. leguminosarum biovars viciae or trifolii, or from R. meliloti. Three inducers are 'common', three others almost exclusively induce the nodA promoter in the presence of the R. leguminosarum biovar viciae nodD gene, and the last one is active with the noD genes of either R. leguminosarum biovar viciae or that of R. meliloti. Testing of a large number of flavonoids revealed two classes of structural features required for inducing ability: (i) features required for induction in general, and (ii), features restricting the inducing ability to (a) specific nodD gene(s). These features are discussed in relation to current models of the process of nodD-mediated transcription activation of the inducible nod genes.