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At least 1,171 records · Page 65Linked to original sources
PubMed2001

Resistance of a soybean cell line to oxyfluorfen by overproduction of mitochondrial protoporphyrinogen oxidase.

The diphenyl ether herbicide oxyfluorfen (2-chloro-4-trifluoromethylphenyl 3-ethoxy-4-nitrophenyl ether) inhibits protoporphyrinogen oxidase (Protox) which catalyzes the oxidation of protoporphyrinogen IX (Protogen) to protoporphyrin IX (Proto IX), the last step of the common pathway to chlorophyll and haeme biosynthesis. We have selected an oxyfluorfen-resistant soybean cell line by stepwise selection methods, and the resistance mechanism has been investigated. No growth inhibition was observed in resistant cells at a concentration of 10(-7) M oxyfluorfen, a concentration at which normal cells did not survive. While the degree of inhibition of total extractable Protox by oxyfluorfen was the same in both cell types, the enzyme activity in the mitochondrial fraction from non-treated resistant cells was about nine-fold higher than that from normal cells. Northern analysis of mitochondrial Protox revealed that the concentration of mitochondrial Protox mRNA was much higher in resistant cells than that in normal cells. There were no differences in the absorption and metabolic breakdown of oxyfluorfen. The growth of resistant cells was also insensitive to oxadiazon [5-tert-butyl-3-(2,4-dichloro-5-isopropoxyphenyl)-1,3,4-oxadiazol-2-(3H)- one], the other chemical class of Protox inhibitor. Therefore, the resistance of the selected soybean cell line to oxyfluorfen is probably mainly due to the overproduction of mitochondrial Protox.

Blotting, Northern↗
PubMed1996

Primary structure and expression of plant homologues of animal and fungal thioredoxin-dependent peroxide reductases and bacterial alkyl hydroperoxide reductases.

Higher plants express genes encoding peroxiredoxins of the two-cysteine type. This is concluded from the isolation of cDNAs from spinach (Spinacia oleracea) and barley (Hordeum vulgare cv. Gerbel) which are homologous to animal, fungal, and bacterial two-cysteine peroxiredoxins. Northern blot analysis indicated the presence of at least one corresponding gene in all angiosperms analyzed suggesting that bas1 is a member of an ubiquitous gene family encoding a protein of fundamental importance in oxidative stress defense also in plants. In barley, expression increased upon application of methyl viologen but was not affected by ozone. mRNA levels increased during deetiolation in the light. Maximal abundance of bas1 transcripts was observed in young developing shoot segments where cell division and elongation take place. Expression was insignificant in roots. The amount of bas1 protein was high in the leaf blade, particularly in etiolated plants, and did not respond to oxidative stress. bas1 protein was not detected in roots. From our data, we suggest that bas1 is an antioxidant enzyme particularly important in the developing shoot and photosynthesizing leaf.

Amino Acid Sequence↗
PubMed1997

The endomembrane sheath: a key structure for understanding the plant cell?

Recent evidence suggests that integrin is abundant in endomembranes of plant cells, and the endomembranes are clad by a sheath of cytoskeleton including F-actin. A role for endomembrane integrin and the endomembrane sheath is proposed: this system might orchestrate metabolic regulation by providing and modulating loci for channelling, and might accelerate channeling as needed by dragging the endoplasmic reticulum (ER) and organelles through the cytoplasm. To accomplish this "streaming", F-actin might lever against the rest of the endomembrane sheath and the ER might also lever against adhesion sites (i.e., plasmodesmata and plasmalemmal control centers). As an important agent in the control of cellular activities, according to this model, the endomembrane sheath would play a major part in responses to diverse signals and stresses, and under extreme stress cell survival would depend on the ability of the system to maintain enough integrity to direct critical syntheses and degradations.

Actins↗
PubMed2003

Ecophysiological aspects of allelopathy.

Allelochemicals play an important role in explaining plant growth inhibition in interspecies interactions and in structuring the plant community. Five aspects of allelochemicals are discussed from an ecophysiological perspective: (i) biosynthesis, (ii) mode of release, (iii) mode of action, (iv) detoxification and prevention of autotoxicity, and (v) joint action of allelochemicals. A discussion on identifying a compound as an allelochemical is also presented.

Ecology↗
PubMed1976

Physical studies on the size and structure of the covalently closed circular chloroplast DNA from higher plants.

The size and structure of the covalently closed circular chloroplast DNAs (ctDNA) from pea, lettuce, and spinach plants, have been studied by analytical ultracentrifugation. The values of so20,w,Na+ of the native and denatured forms of the open and closed circular DNAs from these plants have been determined. The absolute molecular weight of purified closed circular pea ctDNA monomers has been determined by buoyant equilibrium sedimentation to be 89.1 (S.D. +/- 0.7)-10(6). The value of the so20,w,Na+ of open circular pea ctDNA and its molecular weight, in conjunction with corresponding values for other sizes of circular DNA, has been used to derive an empirical relationship between so20,w,Na+ and molecular weight for open circular DNAs. Using this relationship, the molecular weights of lettuce and spinach ctDNAs have been determined to be 98.2 (S.D. +/- 1.5)-10(6) and 97.2 (S.D. +/- 1.5)-10(6), respectively. At pH values 12.7 and 13, closed circular lettuce and pea ctDNAs have been found to exist as mixtures of reversibly and irreversibly denatured closed circular DNAs.

Animals↗
PubMed1996

Further polyoxypregnanes from Marsdenia tenacissima.

Two new polyoxypregnanes, designated marstenacigenins A and B, along with a known compound, dresgenin, were isolated from the mild acid hydrolysate of the ethanol extract of the stems of Marsdenia tenacissima. Their structures were deduced by a combination of 1D and 2D NMR spectroscopic techniques as 12 beta-cinnamoyl-dihydrosarcostin and 12 beta,20-dibenzoyldihydrosarcostin, respectively.

Magnetic Resonance Spectroscopy↗
PubMed1995

Three diterpene dilactone glycosides from Podocarpus nagi.

Three water-soluble constituents, nagilactosides C-E, were isolated from Podocarpus nagi. Their structures were determined by chemical and spectroscopic methods, respectively. Nagilactoside C was identified as 1-deoxy-nagilactone A-2 alpha-O-beta-D-glucopyranosyl-(1-->3)-beta-D-glucopyranoside, nagilactoside D as 1-deoxy-nagilactone A-2 alpha-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranoside, and nagilactoside E as nagilactone A-1 beta-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyransoide.

Carbohydrate Conformation↗
PubMed1984

The influence of gravity on the structure and functions of plant material.

Growth process generate plant form and relate to most physiological functions. The Earth's gravity force affects plant growth in both obvious and subtle ways. It is a major environmental influence on morphology and physiology of plants. Gravity is less important as an agent for plant stress than as an environmental signal to guide growth. The plant's bioaccelerometers are remarkably sensitive, especially in hypogravity. Simulation (clinostat) studies and experiments in satellite laboratories are needed to understand the sensing, transduction, and response characteristics of g related mechanisms. By examining how plants alter growth processes to accomplish developmental or physiological "objectives" we may find it pragmatically desirable to ask ourselves how we might design a plant to achieve such responses to environmental influences. Examples of this design engineering approach for gravity related effects are described as an aid to experimentation.

Biological Transport↗
PubMed2005

Profiling of structurally labile oxylipins in plants by in situ derivatization with pentafluorobenzyl hydroxylamine.

A GC-MS-based method for the simultaneous quantification of common oxylipins along with labile and highly reactive compounds based on in situ derivatization with pentafluorobenzyl hydroxylamine to the corresponding O-2,3,4,5,6-pentafluorobenzyl oximes (PFB oximes) is presented. The approach covers oxo derivatives such as jasmonic acid (JA), 12-oxophytodienoic acid (OPDA), certain phytoprostanes, unsaturated oxo-acids, oxo-hydroxy acids, and aldehyde fragments from the polar head of fatty acids. In the positive electron impact-MS mode, the PFB oximes display characteristic fragment ions that greatly facilitate the identification of oxylipins in complex matrices. In addition, the fluorinated derivatives allow a highly selective and low-background analysis by negative chemical ionization. Besides showing the general value of the method for the identification of a broad range of oxylipins (18 examples), we also demonstrate sensitivity, linearity, and reproducibility for the quantification of JA, OPDA, 11-oxo-9-undecenoic acid, and 13-oxo-9,11-tridecadienoic acid. The efficiency of the method is demonstrated by differential profiling of these four oxylipins in lima bean leaves after mechanical wounding and feeding by the herbivore Spodoptera littoralis. Caterpillar feeding induced several oxylipins, whereas after wounding only the level of JA increased. The rapid in situ derivatization prevents the isomerization of cis-JA to trans-JA. The resting level of JA in lima beans showed an isomer ratio of 80:20 for trans/cis-JA. After wounding, de novo synthesis of JA alters the ratio to 20:80 in favor of the cis isomer.

Animals↗
PubMed2003

A rapid screening assay for inhibitors of 11beta-hydroxysteroid dehydrogenases (11beta-HSD): flavanone selectively inhibits 11beta-HSD1 reductase activity.

A rapid screening assay for chemicals inhibiting 11beta-hydroxysteroid dehydrogenase (11beta-HSD) type 1 or type 2 using lysates from stably transfected cells was developed. Here, we tested a series of environmental chemicals for anti-11beta-HSD activities. Inhibition of 11beta-HSD2, which may cause cortisol-dependent activation of the mineralocorticoid receptor with sodium retention and hypertension, was observed for several compounds, with diethylcarbamate being the most potent inhibitor (IC50 6.3 microM). Abietic acid inhibited both 11beta-HSD1 (IC50 27 microM for reduction and 2.8 microM for oxidation) and 11beta-HSD2 (IC50 12 microM). Our results demonstrate for the first time that flavanone selectively inhibits 11beta-HSD1 reductase activity: this enzyme being considered as essential for the local activation of glucocorticoids and representing a potential target for the therapeutic treatment of diabetes type 2. Flavanone and 2'-hydroxyflavanone efficiently inhibited reductive (IC50 18 and 10 microM) but not oxidative activity. We observed a reduced inhibitory effect of hydroxylated flavanone derivatives and of flavones containing a double-bond between atom C2 and C3. Flavanone was specific for 11beta-HSD1 and did not inhibit 11beta-HSD2. Our results reveal that a variety of environmental compounds exert distinct inhibitory effects on 11beta-HSD1 and 11beta-HSD2, opening the possibility for selectively modulating local cortisone/cortisol availability in vivo.

11-beta-Hydroxysteroid Dehydrogenase Type 1↗
PubMed2005

Engineering of plant natural product pathways.

Although many important and valuable traits are associated with plant natural products, engineering natural product pathways for plant improvement has often been limited by a lack of understanding of their biochemistry, and by the need for coordinate regulation of multiple gene activities. New approaches are facilitating both the discovery of genes that encode natural products and pathway engineering. Notable successes have been reported in altering complex pathways to improve plant quality and resistance to biotic and abiotic stresses.

Biological Factors↗
PubMed2005

Plant secondary metabolism glycosyltransferases: the emerging functional analysis.

Glycosylation is a widespread modification of plant secondary metabolites. It is involved in various functions, including the regulation of hormone homeostasis, the detoxification of xenobiotics and the biosynthesis and storage of secondary compounds. In plants, these reactions are controlled by a specific subclass of the ubiquitous glycosyltransferase family. Although these enzymes have been studied intensively for many years, to date only a handful have been characterized in planta. Plant genome projects have uncovered unsuspected complexity within this family that is hindering the characterization of single genes. However, genome information also paves the way for the development of functional genomic approaches. Here, we highlight recent progress and the outcomes of novel strategies developed to uncover the physiological roles of these glycosyltransferases.

Genome, Plant↗
PubMed2004

The Vr-PLC3 gene encodes a putative plasma membrane-localized phosphoinositide-specific phospholipase C whose expression is induced by abiotic stress in mung bean (Vigna radiata L.).

Phosphoinositide-specific phospholipase C (PI-PLC) catalyzes the hydrolysis of phosphatidylinositol 4,5-bisphosphate to generate inositol 1,4,5-trisphosphate and diacylglycerol, both of which act as secondary messengers in animal cells. In this report, we identified in Vigna radiata L. (mung bean) three distinct partial cDNAs (pVr-PLC1, pVr-PLC2, and pVr-PLC3), which encode forms of putative PI-PLC. All three Vr-PLC genes were transcriptionally active and displayed unique patterns of expression. The Vr-PLC1 and Vr-PLC2 transcripts were constitutively expressed to varying degrees in every tissue of mung bean plants examined. In contrast, the Vr-PLC3 mRNA level was very low under normal growth conditions and was rapidly induced in an abscisic acid-independent manner under environmental stress conditions (drought and high salinity). An isolated genomic clone, about 8.2 kb in length, showed that Vr-PLC1 and Vr-PLC3 are in tandem array in the mung bean genome. The predicted primary sequence of Vr-PLC3 (M(r)=67.4 kDa) is reminiscent of the delta-isoform of animal enzymes which contain core sequences found in typical PI-PLCs, such as the catalytic domain comprising X and Y motifs, a lipid-binding C2 domain, and the less conserved EF-hand domain. Results of in vivo targeting experiment using a green fluorescent protein (GFP) showed that the GFP-Vr-PLC3 fusion protein was localized primarily to the plasma membrane of the Arabidopsis protoplast. The C2 domain was essential for Vr-PLC3 to be targeted to the plasma membrane. The possible biological functions of stress-responsive Vr-PLC3 in mung bean plants are discussed.

Amino Acid Sequence↗