Showing papers on "Amaranthus hypochondriacus published in 2000"

Increased nutritive value of transgenic potato by expressing a nonallergenic seed albumin gene from Amaranthus hypochondriacus

Abstract: Improvement of nutritive value of crop plants, in particular the amino acid composition, has been a major long-term goal of plant breeding programs. Toward this end, we reported earlier the cloning of the seed albumin gene AmA1 from Amaranthus hypochondriacus. The AmA1 protein is nonallergenic in nature and is rich in all essential amino acids, and the composition corresponds well with the World Health Organization standards for optimal human nutrition. In an attempt to improve the nutritional value of potato, the AmA1 coding sequence was successfully introduced and expressed in tuber-specific and constitutive manner. There was a striking increase in the growth and production of tubers in transgenic populations and also of the total protein content with an increase in most essential amino acids. The expressed protein was localized in the cytoplasm as well as in the vacuole of transgenic tubers. Thus we have been able to use a seed albumin gene with a well-balanced amino acid composition as a donor protein to develop a transgenic crop plant. The results document, in addition to successful nutritional improvement of potato tubers, the feasibility of genetically modifying other crop plants with novel seed protein composition.

Digestive amylase from the larger grain borer, Prostephanus truncatus Horn.

Abstract: A combination of ion-exchange chromatography, preparative electrophoresis and gel filtration chromatography allowed a 1209-fold purification of one of the two major digestive α-amylases from larvae of the larger grain borer, Prostephanus truncatus Horn. The purified enzyme showed a molecular mass of 60.2 kDa, an isoelectric point of 4.7 and an optimal pH for activity of 6.0. The enzyme was heat labile and it was recognized by proteinaceous inhibitors from amaranth seeds (Amaranthus hypochondriacus), whereas extracts from maize (Zea mays) and tepary bean (Phaseolus acutifolius) produced very low inhibition. When the enzyme was measured at different stages of development, maximal activity was found in the second instar larvae. Activity drastically decreased to a very low level during the pupae stage and increased again at the adult stage. A zymogram of the different developmental stages showed two main bands of α-amylase activity, which almost disappeared at the pupae stage to increase again during the adult stage, revealing a new, smaller band. This new band may be required for a better adaptation of the adult insect to its new environment.

Effect of lichen metabolites on thylakoid electron transport and photophosphorylation in isolated spinach chloroplasts.

Abstract: Investigation of the lichen Parmotrema tinctorum led to the isolation of several known compounds. Among them, lecanorin (1), methyl-β-orcinol carboxylate, methyl orsellinate, orcinol, and methyl haematommate (3) caused significant inhibition of the radicle growth and germination of seedlings of Amaranthus hypochondriacus and Echinochloa crusgalli. In addition, lecanorin (1) and gyrophoric acid (2) significantly inhibited the light-dependent synthesis of ATP and uncoupled electron transfer on the reducing side of photosystem II in freshly lysed, illuminated spinach chloroplasts. The targets of 1 and 2 were located at the water-splitting enzyme level and in one of the redox enzymes in the range of electron transport from P680 to QA, respectively.

Phytotoxic compounds from the new coprophilous fungus guanomyces polythrix.

Abstract: Bioactivity-directed fractionation of the fermentation broth and mycelium of the coprophilous fungus Guanomyces polythrix led to the isolation of several phytotoxic compounds, including five new naphthopyranone derivatives (1-5). In addition, rubrofusarin B, emodin, citrinin, and 4-hydroxybenzoic acid methyl ester were obtained. The structures of the new compounds were established by spectral and chiroptical methods. The isolates caused significant inhibition of radicle growth of two weed seedlings (Amaranthus hypochondriacus and Echinochloa crusgalli) and interacted with both spinach and bovine brain calmodulins.

Illumination increases the affinity of phosphoenolpyruvate carboxylase to bicarbonate in leaves of a C4 plant, Amaranthus hypochondriacus.

Abstract: Illumination increased markedly the affinity to bicarbonate of phosphoenolpyruvate carboxylase (PEPC; EC 4.1.1.31) in leaves of Amaranthus hypochondriacus L., a C4 plant. When leaves were illuminated, the apparent Km for (HCO3-) of PEPC decreased by about 50% concurrent with a 2- to 5-fold increase in Vmax and 3- to 4-fold increase in Ki for malate. The inclusion of ethoxyzolamide, an inhibitor of carbonic anhydrase, during the assay had no effect on kinetic and regulatory properties of PEPC indicating that carbonic anhydrase was not involved during light-induced sensitization of PEPC to HCO3-. Pretreatment of leaf discs with cycloheximide (CHX), a cytosolic protein synthesis inhibitor, suppressed significantly the light-enhanced decrease in apparent Km (HCO3-). Further, in vitro phosphorylation of purified dark-form PEPC by protein kinase A (PKA) decreased the apparent Km (HCO3-) of the enzyme, in addition increasing Ki (malate) as expected. Such changes, due to in vitro phosphorylation of purified PEPC by PKA, occurred only with wild-type PEPC, but not in the mutant form of maize (S15D) which is already a mimic of the phosphorylated enzyme. These results suggest that phosphorylation of the enzyme is important during the sensitization of PEPC to HCO3- by illumination in C4 leaves. Since illumination is expected to increase the cytosolic pH and the availability of dissolved HCO3- in mesophyll cells, the sensitization by light of PEPC to HCO3- could be physiologically quite significant.

First report of the characterization of the threatened plant species Amaranthus pumilus (Seabeach amaranth).

Abstract: This paper reports the first ever investigation of the chemical components/composition of the seeds of Amaranthus pumilus (a threatened amaranth species) and compares the results to those of the more commonly cultivated Amaranthus hypochondriacus (Plainsman). This study clearly revealed that much genetic diversity exists between these species, indicating that potential breeding possibilities for the improvement of more commonly cultivated amaranth lines do exist. A. pumilus offers a much larger and more desirable seed size and weight (2-3-fold higher), permitting greater biomass production, in addition to lower levels (half) of free carbohydrate for improved value/performance in diabetic-type diets. In addition to the higher edible oil content found in A. pumilus, its lower saturated/unsaturated ratio (one of the lowest thus far measured) makes it potentially a better source of nutritional oil. In addition to the 2-fold-higher quantity of vitamin E found in A. pumilus, the higher levels of squalene also found may one day serve as a renewable crop source of this compound and may diminish the world's dependence upon marine animals. Considering the imminent danger posed to the survival of the seabeach amaranth in its native environment, it is hoped this study will raise public awareness of the importance of this species and thereby protect it from reaching extinction.

Phytotoxic compounds from Xanthocephalum gymnospermoides var. eradiatum.

Abstract: Investigation of the aerial parts of Xanthocephalum gymnospermoides var eradiatum led to the isolation of two new labdane-type of diterpenes, namely, 8 alpha,13S-epoxylabdane-14S,15-diol (1) and methyl grindelate (2). In addition, grindelic acid (3), 7 alpha, 8 alpha-epoxygrindelic acid (4), 7 alpha-hydroxy-8(17)dehydrogrindelic acid (5), 17-hydroxygrindelic acid (6) and 4,5-epoxy-beta-caryophyllene (7) were obtained. The isolated compounds were characterized by spectral means. The absolute configuration of compound 1 was established by chemical correlation with 8 alpha,13S-epoxy-15-nor-labdan-14-oic acid methyl ester of known absolute stereochemistry and by using the advanced Mosher's ester methodology. The results of the present investigation indicated that the known compound barbatol (8) could be an enantiomer of compound 1. Compounds 1-3 and 7 caused significant inhibition of the radicle growth of seedlings of Amaranthus hypochondriacus.

Modulation of phosphoenolpyruvate carboxylase phosphorylation in leaves of Amaranthus hypochondriacus, a NAD-ME type of C4 plant.

Abstract: PEP carboxylase (PEPC) in leaves of C4 plants is activated by phosphorylation of enzyme by a PEPC-protein kinase (PEPC-PK). We reevaluated the pattern of PEPC phosphorylation in leaf extracts of Amaranthus hypochondriacus. It was dependent on Ca2+, the optimum concentration of which for stimulation was 10 mM. The extent of stimulation was inhibited by 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA), a Ca2+ chelator. The inhibition by BAPTA was relieved by the addition of Ca2+ but not by the addition of Mg2+. The stimulation by Ca2+ of PEPC phosphorylation was marginally enhanced by calmodulin (CaM), but not by diacylglycerol (DAG). Phosphorylation was strongly restricted by Ca2+ or Ca2+-CaM-dependent protein kinase inhibitors. Thus phosphorylation of PEPC is Ca2+-dependent in leaves of A. hypochondriacus and a calcium-dependent protein kinase (CDPK) may modulate PEPC-PK and subsequently the phosphorylation status of PEPC.

Purification and Stability during Storage of Phoshoenolpyruvate Carboxylase from Leaves of Amaranthus hypochondriacus, a NAD-ME Type C4 Plant

Abstract: A traditional method is reported for purification of phosphoenolpyruvate carboxylase (PEPC; EC 41131) from leaves of Amaranthus hypochondriacus L with a high yield of 50 %, 135-fold purification, and specific activity of 900 mmol kg−1(protein) s−1 PEPC was purified from light-adapted leaves of A hypochondriacus, involving 40–60 % ammonium sulphate fractionation, followed by chromatography on columns of DEAE-Sepharose, hydroxylapatite (HAP), and Seralose 6-B The enzyme appeared as a single band on 10 % SDS-PAGE, with a molecular mass of about 100 kDa Kinetic studies with purified enzyme confirmed the PEPC to be the light-form of the enzyme Glycerol generally increased the stability of PEPC The stability and storage of the purified enzyme was studied at temperatures of 4 °C, −20 °C, and liquid nitrogen PEPC maintained its activity for up to 3 months upon storage with 50 % (v/v) glycerol in liquid nitrogen

Separation of the Pigment of an Amaranth

Abstract: It is known that current quality requirements require the utilization of natural colorants in the foods. The objective of the present work is to extract the pigment amaranthus from fresh leaves of Amaranthus hypochondriacus L. cv Don Pedro to characterize it through spectroscopic techniques, to be used as natural colorants.