Biosynthesis of L-ascorbic acid and conversion of carbons 1 and 2 of L-ascorbic acid to oxalic acid occurs within individual calcium oxalate crystal idioblasts.
L-Ascorbic acid (AsA) and its metabolic precursors give rise to oxalic acid (OxA) found in calcium oxalate crystals in specialized crystal idioblast cells in plants; however, it is not known if AsA and OxA are synthesized within the crystal idioblast cell or transported in from surrounding mesophyll cells. Isolated developing crystal idioblasts from Pistia stratiotes were used to study the pathway of OxA biosynthesis and to determine if idioblasts contain the entire path and are essentially independent in OxA synthesis. Idioblasts were supplied with various (14)C-labeled compounds and examined by micro-autoradiography for incorporation of (14)C into calcium oxalate crystals. [(14)C]OxA gave heavy labeling of crystals, indicating the isolated idioblasts are functional in crystal formation. Incubation with [1-(14)C]AsA also gave heavy labeling of crystals, whereas [6-(14)C]AsA gave no labeling. Labeled precursors of AsA (L-[1-(14)C]galactose; D-[1-(14)C]mannose) also resulted in crystal labeling, as did the ascorbic acid analog, D-[1-(14)C]erythorbic acid. Intensity of labeling of isolated idioblasts followed the pattern OxA > AsA (erythorbic acid) > L-galactose > D-mannose. Our results demonstrate that P. stratiotes crystal idioblasts synthesize the OxA used for crystal formation, the OxA is derived from the number 1 and 2 carbons of AsA, and the proposed pathway of ascorbic acid synthesis via D-mannose and L-galactose is operational in individual P. stratiotes crystal idioblasts. These results are discussed with respect to fine control of calcium oxalate precipitation and the concept of crystal idioblasts as independent physiological compartments. (+info)
Interaction of sulfate assimilation with carbon and nitrogen metabolism in Lemna minor.
Cysteine synthesis from sulfide and O-acetyl-L-serine (OAS) is a reaction interconnecting sulfate, nitrogen, and carbon assimilation. Using Lemna minor, we analyzed the effects of omission of CO(2) from the atmosphere and simultaneous application of alternative carbon sources on adenosine 5'-phosphosulfate reductase (APR) and nitrate reductase (NR), the key enzymes of sulfate and nitrate assimilation, respectively. Incubation in air without CO(2) led to severe decrease in APR and NR activities and mRNA levels, but ribulose-1,5-bisphosphate carboxylase/oxygenase was not considerably affected. Simultaneous addition of sucrose (Suc) prevented the reduction in enzyme activities, but not in mRNA levels. OAS, a known regulator of sulfate assimilation, could also attenuate the effect of missing CO(2) on APR, but did not affect NR. When the plants were subjected to normal air after a 24-h pretreatment in air without CO(2), APR and NR activities and mRNA levels recovered within the next 24 h. The addition of Suc and glucose in air without CO(2) also recovered both enzyme activities, with OAS again influenced only APR. (35)SO(4)(2-) feeding showed that treatment in air without CO(2) severely inhibited sulfate uptake and the flux through sulfate assimilation. After a resupply of normal air or the addition of Suc, incorporation of (35)S into proteins and glutathione greatly increased. OAS treatment resulted in high labeling of cysteine; the incorporation of (35)S in proteins and glutathione was much less increased compared with treatment with normal air or Suc. These results corroborate the tight interconnection of sulfate, nitrate, and carbon assimilation. (+info)
Fatty acid composition of Dracunculus vulgaris Schott (Araceae) seed oil from Turkey.
Dracunculus vulgaris Schott is only one taxon of the genus Dracunculus (Araceae) in Turkey. The tubers and the fruits with the seeds of D. vulgaris have long been in use for the treatment of rheumatism and hemorrhoids, respectively. The fatty acid composition of D. vulgaris seeds have been analyzed as their methyl esters by GC and GC-mass spectrometry. C16:0, C16:1n-7, C18:1n-9, C18:1n-7 (cis -vaccenic acid), C18:2n-6 and 13-phenyl tridecanoic acids were found to be the main components in the seed oil. (+info)
Identification of Streptomyces coelicolor proteins that are differentially expressed in the presence of plant material.
Streptomyces coelicolor and Lemna minor were used as a model to study the modulation of bacterial gene expression during plant-streptomycete interactions. S. coelicolor was grown in minimal medium with and without L. minor fronds. Bacterial proteomes were analyzed by two-dimensional gel electrophoresis, and a comparison of the two culture conditions resulted in identification of 31 proteins that were induced or repressed by the presence of plant material. One-half of these proteins were identified by peptide mass fingerprinting by using matrix-assisted laser desorption ionization-time of flight mass spectrometry. The induced proteins were involved in energetic metabolism (glycolysis, pentose phosphate pathway, oxidative phosphorylation), protein synthesis, degradation of amino acids, alkenes, or cellulose, tellurite resistance, and growth under general physiological or oxidative stress conditions. The repressed proteins were proteins synthesized under starvation stress conditions. These results suggest that root exudates provide additional carbon sources to the bacteria and that physiological adaptations are required for efficient bacterial growth in the presence of plants. (+info)
Isolation of a crystal matrix protein associated with calcium oxalate precipitation in vacuoles of specialized cells.
The formation of calcium (Ca) oxalate crystals is considered to be a high-capacity mechanism for regulating Ca in many plants. Ca oxalate precipitation is not a stochastic process, suggesting the involvement of specific biochemical and cellular mechanisms. Microautoradiography of water lettuce (Pistia stratiotes) tissue exposed to 3H-glutamate showed incorporation into developing crystals, indicating potential acidic proteins associated with the crystals. Dissolution of crystals leaves behind a crystal-shaped matrix "ghost" that is capable of precipitation of Ca oxalate in the original crystal morphology. To assess whether this matrix has a protein component, purified crystals were isolated and analyzed for internal protein. Polyacrylamide gel electrophoresis revealed the presence of one major polypeptide of about 55 kD and two minor species of 60 and 63 kD. Amino acid analysis indicates the matrix protein is relatively high in acidic amino acids, a feature consistent with its solubility in formic acid but not at neutral pH. 45Ca-binding assays demonstrated the matrix protein has a strong affinity for Ca. Immunocytochemical localization using antibody raised to the isolated protein showed that the matrix protein is specific to crystal-forming cells. Within the vacuole, the surface and internal structures of two morphologically distinct Ca oxalate crystals, raphide and druse, were labeled by the antimatrix protein serum, as were the surfaces of isolated crystals. These results demonstrate that a specific Ca-binding protein exists as an integral component of Ca oxalate crystals, which holds important implications with respect to regulation of crystal formation. (+info)
Genetic relationships of Aglaonema species and cultivars inferred from AFLP markers.
BACKGROUND AND AIMS: Aglaonema is an important ornamental foliage plant genus, but genetic relationships among its species and cultivars have not been reported. This study analysed genetic relatedness of 54 cultivars derived from nine species using amplified fragment length polymorphism (AFLP) markers. METHODS: Initially, 48 EcoRI + 2/MseI + 3 primer set combinations were screened, from which six primer sets that showed clear scoreable and highly polymorphic fragments were selected and used for AFLP reactions. AFLP fragments were scored and entered into a binary data matrix as discrete variables. Jaccard's coefficient of similarity was calculated for all pair-wise comparisons among the 54 cultivars, and a dendrogram was constructed by the unweighted pair-group method using the arithmetic average (UPGMA). KEY RESULTS: The number of AFLP fragments generated per primer set ranged from 59 to 112 with fragment sizes varying from 50 to 565 bp. A total of 449 AFLP fragments was detected, of which 314 were polymorphic (70 %). All cultivars were clearly differentiated by their AFLP fingerprints. The 54 cultivars were divided into seven clusters; cultivars within each cluster generally share similar morphological characteristics. Cluster I contains 35 cultivars, most of them are interspecific hybrids developed mainly from A. commutatum, A. crispum or A. nitidum. However, Jaccard's similarity coefficients among these hybrids are 0.84 or higher, suggesting that these popular hybrid cultivars are genetically much closer than previously thought. This genetic similarity may imply that A. nitidum and A. crispum are likely progenitors of A. commutatum. CONCLUSIONS: Results of this study demonstrate the efficiency and ease of using AFLP markers for investigating genetic relationships of ornamental foliage plants, a group usually propagated vegetatively. The AFLP markers developed will help future Aglaonema cultivar identification, germplasm conservation and new cultivar development. (+info)
Effects of a PAL inhibitor on phenolic accumulation and UV-B tolerance in Spirodela intermedia (Koch.).
Duckweed (Spirodela intermedia) was grown axenically on 1/2 strength Hutner's nutrient solution plus 1% sucrose, with the l-phenylalanine ammonia-lyase (PAL) inhibitor 2-aminoindan-2-phosphonic acid (AIP) at 0.0, 0.05, or 10 microM, at constant 25 degrees C and a light intensity of 300 micromol m(-2) s(-1) photosynthetically active radiation from CW fluorescent lamps. Growth with 10 microM AIP led to decreased frond area and fresh weight, but dry weight was unchanged. Microscopic examination of fronds revealed increased frond thickness and a lack of reticulate aerenchyma. Ultraviolet epifluorescence microscopy and UV-Vis spectroscopy of methanolic extracts confirmed the dose-dependent inhibition of secondary phenolic synthesis with the near total elimination of secondary phenolic accumulation at the 10 microM level. AIP-treated plants showed increased sensitivity to UV-B as shown by a reduced F(v)/F(m). The results provided direct evidence of the working hypothesis that phenols function to screen UV radiation from reaching photosynthetic tissues or damaging other sensitive tissues. A novel histochemical method employing zirconyl chloride to visualize phenols is discussed. (+info)
Coronamycins, peptide antibiotics produced by a verticillate Streptomyces sp. (MSU-2110) endophytic on Monstera sp.
Coronamycin is a complex of novel peptide antibiotics with activity against pythiaceous fungi and the human fungal pathogen Cryptococcus neoformans. It is also active against the malarial parasite, Plasmodium falciparum, with an IC(50) of 9.0 ng ml(-1). Coronamycin is produced by a verticillate Streptomyces sp. isolated as an endophyte from an epiphytic vine, Monstera sp., found in the Manu region of the upper Amazon of Peru. Bioassay-guided fractionation of the fermentation broths of this endophyte on silica gel and HPLC chromatography yielded two principal, inseparable, peptides with masses of 1217.9 and 1203.8 Da. Three other minor, but related components, are also present in the preparation. Amino acid analysis of coronamycin revealed residues of component 1, component 2, methionine, tyrosine and leucine at a ratio of 2:2:1:1:3. Other compounds with antifungal activities are also produced by this endophytic streptomycete. (+info)