Movement of a bean shoot: an introduction to chronobiology

An active learning exercise that focuses on movements (circumnutations) of climbing bean plants (Phaseolus vulgaris L.; cv. Kentucky Wonder, pole bean) has been successfully incorporated into the curriculum of educational institutions to introduce the subject of chronobiology to students. This didactic activity, which involves an ultradian rhythm, can be completed within a span of 2-4 h, fits into the schedule of various courses, uses materials commonly found in classrooms, requires a time commitment of only a few minutes from each student, and can be modified to include a circadian rhythm project. Ultimately, students develop a better understanding about parameters and characteristics of rhythms, analytical procedures, and the temporal organization of life.

Efficient but aberrant cleavage of mitochondrial precursor proteins by the chloroplast stromal processing peptidase

Cytosol-synthesized chloroplast and mitochondrial precursor proteins are proteolytically processed after import by highly specific, metal-dependent soluble enzymes: the stromal processing peptidase (SPP) and the matrix processing peptidase (MPP), respectively. We have used in vitro processing assays to compare the reaction specificities of highly purified preparations of pea SPP and Neurospora crassa MPP, both of which are unable to cleave a variety of 'foreign' proteins. We show that SPP can cleave all five mitochondrial precursor proteins tested, namely cyclophilin, the beta subunit of the F1-ATPase complex, the Rieske FeS protein, the alpha-MPP subunit and cytochrome b2. In contrast, MPP is unable to cleave any chloroplast precursor proteins tested. Several of the mitochondrial precursor proteins are cleaved more efficiently by SPP than are many authentic chloroplast precursor proteins but, in each case, cleavage takes place at a site or sites which are N-terminal to the authentic MPP site; pre-cyclophilin is cleaved 5 residues upstream of the MPP site and the precursor of the beta subunit of the F1-ATPase complex is cleaved at sites 5 and 12 residues upstream. We discuss the implications of these data for the SPP reaction mechanism.

Separation of two classes of plastid DNA-dependent RNA polymerases that are differentially expressed in mustard (Sinapis alba L.) seedlings

Chloroplast and etioplast in vitro transcription systems from mustard have different functional properties, which is reflected in differences in phosphorylation status. Here we report another transcription control mechanism, which involves two plastid DNA-dependent RNA polymerases designated as peak A and peak B enzymes. Both are large multi-subunit complexes, but differ in their native molecular mass (> 700 kDa for peak A and ca. 420 kDa for peak B) and in their polypeptide composition. The A enzyme is composed of at least 13 polypeptides, while the B enzyme contains only four putative subunits. Peak B activity is inhibited by rifampicin, whereas that of peak A is resistant. RNA polymerase activity was compared for plastids from cotyledons of 4-day-old seedlings that were grown either under continuous light (chloroplasts) or in darkness (etioplasts), or were first dark-grown and then transferred to light for 16 h ('intermediate-type' plastids). While the total activity was approximately the same in all three cases, enzyme B was the predominant activity obtained from etioplasts and enzyme A that obtained from chloroplasts. Both had equal activity in preparations from the 'intermediate-type' plastid form. Both activation/inactivation and differential gene expression seem to play a role in the regulation of the plastid transcription machinery.

Hypoglycaemic effects of Andrographis paniculata Nees on non-diabetic rabbits

So far known Andrographis paniculata Nees (AP) is a hepatoprotective, antiplatelet and antithrombotic drug. In this experiment its hypoglycaemic effect has been tried in various way. Water extract of AP 10 mg/kg body weight can prevent induction of hyperglycaemia significantly (P < 0.001) induced by oral administration of glucose 2 mg/kg body weight. But any how failed to do so in adrenaline induced hyperglycaemia. It also failed to demonstrate any "fasting blood sugar lowering effect" upon chronic administration (6 weeks) of AP. So probably AP prevents glucose absorption from gut. Whole experiment was done on rabbits.

Observations on the effect of areca nut extracts on oral fibroblast proliferation

The effects of aqueous extracts of raw, baked and boiled areca nuts were tested on cultured human buccal mucosa fibroblasts. Cells were exposed to extract concentrations of 0, 50, 100, 150, 300 and 500 micrograms/ml. The arecoline and arecaidine content was determined in the extracts with HPLC and raw nut contained 5.5% m/m, baked nut 6.6% m/m and boiled nut 7.1% m/m. Extract concentrations of 50 to 150 micrograms/ml inhibited cell growth in a concentration-dependent manner but did not lead to total cell death during a 7 day period. However, total cell death did occur with concentrations of 300 and 500 micrograms/ml. It is concluded that areca nut extract is toxic to cultured fibroblasts and inhibits their proliferation in a concentration-dependent manner.

Antiviral activity of African medicinal plants

Plants from Africa and Mauritius with a history of use in traditional medicine have been investigated for their antiviral activities. Extracts were tested against poliovirus, herpes simplex virus and rhinovirus in plaque reduction assays. Their general toxicity and effects on interferon production were also studied.

Restriction fragment length polymorphism evidence for genetic homology within a pathovar of Pseudomonas syringae

Pseudomonas syringae pv. phaseolicola NPS3121 hrp sequences were used as hybridization probes in a restriction fragment length polymorphism (RFLP) analysis of 24 P. syringae pv. tabaci strains as a means to evaluate the genetic and taxonomic relationship of pathovars of P. syringae. Southern blot analyses of genomic restriction digests, with hrpA-S sequences as hybridization probes, and restriction analyses of PCR-amplified DNA of regions within hrpD were conducted. The resulting RFLP patterns were uniform for 23 of the 24 isolates tested, with strain BR2R having a unique pattern. BR2R is a pathogen of bean which was classified as pathovar tabaci because of its ability to produce tabtoxin, but unlike the other 23 tabaci strains in this study, it does not incite disease symptoms on tobacco. When a DNA fragment containing hrpM sequences was used as a hybridization probe, the tabaci isolates could be divided into three groups on the basis of the RFLP patterns : BR2R, Pt11528R and Pt113R, and the remaining strains. For all of the above analyses, BR2R shared identical RFLP patterns with P. syringae pv. phaseolicola NPS3121, also a bean pathogen which does not cause disease on tobacco. However, BR2R AND NPS3121 could be differentiated from each other on the basis of the RFLP patterns from restriction analysis of PCR-amplified DNA of argF, while the remaining tabaci strains had a third pattern. These studies indicate that hrp genes and argF are conserved in strains of P. syringae pathogenic to tobacco, suggesting that P. syringae strains pathogenic to specific hosts may have a high level of genetic similarity. We believe that these analyses have shown that distinct identifiable genetic differences may be correlated with host range and suggest that such information may be useful for assigning pathovar designations.

Symbiotic host specificity between leguminous plants and rhizobia is determined by substituted and acylated glucosamine oligosaccharide signals

Rhizobia are nitrogen-fixing bacteria which invade root hairs of leguminous plants and induce, in a specific manner, the formation of root nodules in which they fix nitrogen. The early steps of the symbiosis can be considered as a reciprocal molecular communication between the two partners. Initially, the plant excretes a gene inducer which stimulates the expression of bacterial nodulation genes. These nodulation genes are responsible for the synthesis of extracellular host-specific signals, called nodulation factors. The bacterial nodulation factors were isolated and structurally identified as substituted and N-acylated chitin oligosaccharides. These prokaryotic lipo-oligosaccharide signals play a key role in the symbiosis by controlling the host specificity of the bacteria. They constitute a new class of signalling molecules able to elicit nodule organogenesis in leguminous plants in the absence of bacteria.

Inhibition of thromboxane A2 biosynthesis in vitro by the main components of Crataegus oxyacantha (Hawthorn) flower heads

A hydro-alcoholic extract from Crataegus o. (Co) flower heads inhibited thromboxane A2 (TXA2) biosynthesis in vitro. This present study aims to find out which are the active principles. The main components, as revealed by chromatography, were tested. We also took into consideration catechin and epicatechin: although they do not appear as such with chromatography because of their polymerisation or-and condensed structure, these two proanthocyanidins seem to play a major role in the mentioned activity of the plant.

Effect of garlic on lead contents in chicken tissues

Lead has been indicted to be involved in the aetiology of human and animal diseases. In view of earlier literature indicating that garlic antagonized lead toxicity, we have investigated the possible use of garlic feeding to clean up lead contents from chickens which had been exposed to natural or experimental lead pollution and consequently eliminate one of the sources of lead pollution to human consumers. Groups of chickens (10 birds each) were given lead alone (lead acetate equivalent to 5 mg lead/kg B.W.) or both lead and garlic simultaneously or lead followed by garlic post-treatment or garlic alone or distilled water. Lead concentrations were reduced in muscle and liver tissues of chickens given both lead and garlic simultaneously or as a post-treatment. Reduction in tissue-lead concentrations were greater in birds given garlic as a post-treatment than those given garlic simultaneously with lead. The results indicate that garlic contain chelating compounds capable of enhancing elimination of lead. Garlic feeding can be exploited to safeguard human consumers by minimizing lead concentrations in meat of food animals which had been grown in a lead polluted environment.

Interactions of ginseng extract, ginseng separated fractions, and some triterpenoid saponins with glucose transporters in sheep erythrocytes

The effects of Panax ginseng extract, ginseng saponins, and some other triterpenoid saponins on glucose uptake were examined by using sheep erythrocytes. Initial rates of glucose transport were determined by measurements of 2-deoxy-D-glucose (2-DG) uptake. From kinetic analysis apparent Km and Vmax values of facilitated glucose transport in sheep erythrocytes were calculated as 2.3 +/- 0.08 mM and 1.4 +/- 0.05 nmol/min/10(9) cells. The results showed that ginseng extract stimulated glucose uptake in sheep erythrocytes dose-dependently. Ginseng saponins, in general, also stimulated glucose transport. The maximum effect was observed at 1 microM of ginsenoside Rb1 showing an increase of 24 +/- 5% above basal activity. However, ginsenoside Rg3, chikusetsusaponin Ia, and glycyrrhetic acid induced significant inhibitory effects on glucose transport in sheep erythrocytes.

Utility of DNA amplified by degenerate oligonucleotide-primed PCR (DOP-PCR) from the total genome and defined chromosomal regions of field bean

Degenerate oligonucleotide primed (DOP)-PCR has emerged as a simple and rapid method for representative amplification of highly complex genomic DNA from humans, mice and Drosophila. The present paper describes the adaptation of this method for use on a plant species, Vicia faba, with a large genome (2C = 30 pg). Specific low-copy-number sequences as well as highly repeated sequences were detectable among DOP-PCR products obtained from small samples of purified genomic DNA (100 pg), DNA from 10 prophase nuclei, 10 flow-sorted chromosomes or 15 microdissected chromosome segments (satellites) following reamplification with sequence-specific primers and/or Southern hybridization. Biotinylated chromosome-specific DOP-PCR products were used for fluorescent in situ hybridization. All chromosomes showed hybridization signals, with the exception of regions containing Fok elements which are not present in the chromosomal DNA targeted by DOP-PCR.

Bioavailability of glycyrrhizin and licorice extract in rat and human plasma as detected by a HPLC method

The pharmacokinetic behaviour of glycyrrhizin (1) was investigated in order to evaluate the difference in bioavailability after oral administration of licorice extract (LE) or glycyrrhizin (1) to rats and humans. For this study, two reliable HPLC methods were developed for the dosage of the levels of 1 and of its metabolite, the glycyrrhetic acid (2) in plasma samples. The determinations were carried out by HPLC on a reversed phase column with UV detector (251 nm), after a careful extraction step of 1 and 2 from the biological matrix. These methods afford good accuracy and satisfactory precision and they allow the determination of both compounds at levels as low as 200 ng/ml. The analytical results improved the knowledge of 1 pharmacokinetics, showing a significantly reduced bioavailability, when administered as LE compared to 1 when administered as such.

The legumin gene family: a reconstructed Vicia faba legumin gene encoding a high-molecular-weight subunit is related to type B genes

Nucleotide sequence information from a partial genomic clone, a cDNA clone, a RACE clone and a PCR fragment was combined to reconstruct the first reported complete gene sequence encoding a large legumin subunit, designated LelB3. The length difference to the well-characterized major legumin subunits is caused by an extended glutamine/glutamic acid-rich region encoded by the C-terminal part of the alpha chain. Amino acid sequence comparisons reveal that gene LelB3 is more closely related to B-type than to A-type legumin genes of Vicia faba. Gene LelB3 is a member of a small gene family as indicated by published (Pich and Schubert, Biol Zbl 112 (1993); 342-350) and limited own data.

Structure and expression of two plant genes encoding chromoplast-specific proteins: occurrence of partially spliced transcripts

The genes encoding fibrillin and capsanthin-capsorubin synthase are specifically expressed during fruit ripening in Capsicum annuum, leading to the accumulation of these two proteins in chromoplasts. Here, we report for the first time the cloning of genomic DNA fragments encoding these two enzymes, as well as DNA fragments containing upstream regions which are potentially involved in the regulation of the expression of these genes. While the capsanthin-capsorubin synthase gene is uninterrupted, the fibrillin gene is interrupted by two introns, the first one being inefficiently spliced. Occurrence of unspliced transcripts is apparently not related to a post-transcriptional mechanism controlling the synthesis of fibrillin or an alternative polypeptide. This work provides tools for studies on gene activation and intron splicing in plants.

Characterization of binding of Gal beta 4GlcNAc-specific lectins from Erythrina cristagalli and Erythrina corallodendron to glycosphinogolipids. Detection, isolation, and characterization of a novel glycosphinglipid of bovine buttermilk

The lectins from seeds of Erythrina cristagalli and Erythrina corallodendron were characterized for binding to glycolipids, using a chromatogram binding assay, a microtiter well assay, and glycolipids coated on erythrocytes. Both lectins bound to glycolipids having a terminal Gal beta 4GlcNAc sequence and also, with similar affinity, to glycolipids with terminal Fuc alpha 2Gal beta 4GlcNAc (blood group H determinant on a type 2 chain). All other substitutions of Gal beta 4GlcNAc tested abolished the binding. A binding epitope for the Erythrina lectins was considered by comparison of minimum energy conformations of binding and nonbinding glycolipids. A non-acid glycolipid, with lectin binding activity, was found in bovine buttermilk. By mass spectrometry and proton NMR spectroscopy it was shown to be a branched hexaglycosylceramide with the structure Gal beta 4Glc-NAc beta 6(Gal beta 4GlcNAc beta 3)Gal beta 4Glc beta Cer. This glycosphingolipid has not been reported before.

Non-phosphorylating GAPDH of higher plants is a member of the aldehyde dehydrogenase superfamily with no sequence homology to phosphorylating GAPDH

Non-phosphorylating glyceraldehyde 3-phosphate dehydrogenase (GAPDH, NADP-specific, EC 1.2.1.9) operates in the cytosol of autotrophic eukaryotes where it generates NADPH for biosynthetic processes from photosynthetic glyceraldehyde 3-phosphate exported from the chloroplast by the phosphate translocator. Here we report the first cloning and characterization of cDNAs encoding complete polypeptide chains of nonphosphorylating GAPDH from pea and maize by using oligonucleotide probes derived from amino acid sequences determined for the purified enzyme. Unexpectedly, nonphosphorylating GAPDH cannot be aligned with the well-known sequences of phosphorylating GAPDH, but shares about 30% amino acid identity with various specialized and non-specialized aldehyde dehydrogenases (ALDHs) of eubacteria and eukaryotes. A phylogenetic analysis of this ALDH superfamily reveals a complex evolutionary pattern with numerous major branches carrying genes from eubacteria, eukaryotes, or both, encoding enzymes that are specific or non-specific for particular aldehyde substrates. This topology suggests a concomitant emergence of multiple substrate specificities from non-specialized ALDH during an early evolutionary phase of intense metabolic diversification. Although unrelated at the sequence level, non-phosphorylating aldehyde dehydrogenases and phosphorylating GAPDH resemble one another with respect to catalytic hydride transfer and covalent thiol ester formation. Whether or not this reflects an ancestral relationship can only be decided when crystallographic data for ALDH enzymes have become available.

The secA inhibitor, azide, reversibly blocks the translocation of a subset of proteins across the chloroplast thylakoid membrane

The presence of secA and secY gene homologues in the plastid genomes of red algae and cyanophytes has raised the possibility that the products of these genes are involved in protein translocation across the thylakoid membrane. Bacterial SecA proteins are effectively inhibited by azide, and we have tested the effects of this compound on the transport of lumenal proteins across the thylakoid membrane in pea chloroplasts. Recent studies have shown that lumenal proteins are transported by two different mechanisms, one dependent on the thylakoidal delta pH and the other requiring the presence of a stromal protein factor and ATP. In this report we show that azide inhibits the transport across the thylakoid membrane of the latter group of proteins, which includes plastocyanin and the lumenal 33-kDa protein of photosystem II; translocation of proteins by the delta pH-dependent pathway is unaffected. Following import into isolated chloroplasts in the presence of azide, a substantial proportion of plastocyanin and the 33-kDa protein is found as the stromal intermediate form; the proportion increases with lower ATP concentrations, suggesting that azide and ATP may compete for a single site. The presence of azide completely inhibits the import of the 33-kDa protein by isolated thylakoids, but import is restored if the azide is removed from the stromal extract or thylakoids, prior to the import incubation. The data thus indicate that azide reversibly inhibits the transport of a subset of proteins across the thylakoid membrane, consistent with the involvement of a SecA homolog. The results also indicate that azide is potentially a valuable tool for the future assignment of novel lumenal proteins to one of the thylakoidal protein transport mechanisms.

Characterisation and mode of in vitro replication of pea chloroplast OriA sequences

A partially purified replicative system of pea chloroplast that replicates recombinant DNAs containing pea chloroplast origin sequences has been characterised. Polymerisation by this system is very fast and insensitive to chain terminators like dideoxynucleotides, arabinosylcytosine 5'-triphosphate, etc. Both strands of template DNA are synthesized and single-stranded DNA templates undergo more than one round of replication. When sequences of either of the two chloroplast origins of replication (OriA or OriB) are used as templates, the replicative intermediates are found to have sigma structures. Electron microscopic analysis of the sigma structures restricted with various enzymes reveals that the initiation site of in vitro replication maps near the displacement-loop regions where replication initiates also in vivo. Although the observed replication initiation in the OriA recombinant template is chloroplast-DNA-specific, the mode of replication is different from that observed in vivo with intact ctDNA. However, when the template DNA contains both the OriA and OriB sequences, the in vitro replication proceeds in the theta mode, the mode of replication usually observed in vivo.

Targeting of proteins to the thylakoids by bipartite presequences: CFoII is imported by a novel, third pathway

The CFoII subunit of the ATP synthase is an integral component of the thylakoid membrane which is synthesized in the cytosol with a bipartite, lumen-targeting presequence similar in structural terms to those of imported lumenal proteins such as plastocyanin. This presequence is shown to possess a terminal cleavage site for the thylakoidal processing peptidase, but no intermediate site for the stromal processing peptidase. The integration of CFoII into the thylakoid membrane of Pisum sativum has been analysed using in vitro assays for the import of proteins into intact chloroplasts or isolated thylakoids. Efficient integration into thylakoids is observed in the light and dark, and the integration process does not require the presence of either stromal extracts or nucleoside triphosphates. The uncoupler nigericin inhibits integration only very slightly, indicating that the thylakoidal delta pH does not play a significant role in the integration mechanism. In each of these respects, the requirements for CFoII integration differ notably from those determined for integration of the light-harvesting chlorophyll-binding protein of photosystem II. The integration mechanism also differs significantly from the two mechanisms involved in the translocation of lumenal proteins across the thylakoid membrane, since one of these processes requires the presence of stromal protein factors and ATP, and the other mechanism is dependent on the thylakoidal delta pH. This conclusion is reinforced by the finding that saturation of the translocation system for the precursor to the lumenal 23 kDa oxygen-evolving complex protein does not affect integration of CFoII into thylakoids.(ABSTRACT TRUNCATED AT 250 WORDS)