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PubMed2006

The Populus homeobox gene ARBORKNOX1 reveals overlapping mechanisms regulating the shoot apical meristem and the vascular cambium.

Secondary growth is supported by a dividing population of meristematic cells within the vascular cambium whose daughter cells are recruited to differentiate within secondary phloem and xylem tissues. We cloned a Populus Class 1 KNOX homeobox gene, ARBORKNOX1 (ARK1), which is orthologous to Arabidopsis SHOOT MERISTEMLESS (STM). ARK1 is expressed in the shoot apical meristem (SAM) and the vascular cambium, and is down-regulated in the terminally differentiated cells of leaves and secondary vascular tissues that are derived from these meristems. Transformation of Populus with either ARK1 or STM over-expression constructs results in similar morphological phenotypes characterized by inhibition of the differentiation of leaves, internode elongation, and secondary vascular cell types in stems. Microarray analysis showed that 41% of genes up-regulated in the stems of ARK1 over-expressing plants encode proteins involved in extracellular matrix synthesis or modification, including proteins involved in cell identity and signaling, cell adhesion, or cell differentiation. These gene expression differences are reflected in alterations of cell wall biochemistry and lignin composition in ARK1 over-expressing plants. Our results suggest that ARK1 has a complex mode of action that may include regulating cell fates through modification of the extracellular matrix. Our findings support the hypothesis that the SAM and vascular cambium are regulated by overlapping genetic programs.

Amino Acid Sequence↗
PubMed2006

A novel cis-acting element, ESP, contributes to high-level endosperm-specific expression in an oat globulin promoter.

To examine the genetic controls of endosperm (ES) specificity, several cereal seed storage protein (SSP) promoters were isolated and studied using a transient expression analysis system. An oat globulin promoter (AsGlo1) capable of driving strong ES-specific expression in barley and wheat was identified. Progressive 5' deletions and cis element mutations demonstrated that the mechanism of specificity in the AsGlo1 promoter was distinct from that observed in glutelin and prolamin promoters. A novel interrupted palindromic sequence, ACATGTCATCATGT, was required for ES specificity and substantially contributed to expression strength of the AsGlo1 promoter. This sequence was termed the endosperm specificity palindrome (ESP) element. The GCN4 element, which has previously been shown to be required for ES specificity in cereal SSP promoters, had a quantitative role but was not required for tissue specificity. The 960-bp AsGlo1 promoter and a 251-bp deletion containing the ESP element also drove ES-specific expression in stably transformed barley. Reporter gene protein accumulated at very high levels (10% of total soluble protein) in ES tissues of plants transformed with an AsGlo1:GFP construct. Expression strength and tissue specificity were maintained over five transgenic generations. These attributes make the AsGlo1 promoter an ideal promoter for biotechnology applications. In conjunction with previous findings, our data demonstrate that there is more than one genetically distinct mechanism by which ES specificity can be achieved in cereal SSP promoters, and also suggest that there is redundancy between transcriptional and post-transcriptional tissue specificity mechanisms in cereal globulin genes.

Avena↗
PubMed2002

Isolation and characterization of a delta5 FA desaturase from Pythium irregulare by heterologous expression in Saccharomyces cerevisiae and oilseed crops.

By using the polymerase chain reaction approach with two degenerate primers targeting the heme-binding and the third histidine-rich motifs in microsomal carboxyl-directed desaturases, we identified a cDNA PiD5 from Pythium irregulare encoding a delta5 desaturase. The substrate specificity of the enzyme was studied in detail by expressing PiD5 in a yeast (Saccharomyces cerevisiae) mutant strain, AMY-2alpha, where ole1, a delta9 desaturase gene, is disrupted. The result revealed that the encoded enzyme could desaturate unsaturated FA from 16 to 20 carbons beginning with delta9 and delta11 as well as delta8 ethylenic double bonds. Introduction of PiD5 into Brassica juncea under the control of a CaMV 35S constitutive promoter resulted in accumulation of several delta5-unsaturated polymethylene-interrupted FA (delta5-UPIFA) including 18:2-5,9, 18:2-5,11, 18:3-5,9,12, and 18:4-5,9,12,15 in vegetative tissues. The transgenic enzyme could also desaturate the exogenously supplied homo-gamma-linolenic acid (20:3-8,11,14) to arachidonic acid (20:4-5,8,11,14). Introduction of PiD5 into B. juncea and flax under the control of seed-specific promoters resulted in production of delta5-UPIFA, representing more than 10% of the total FA in the seeds.

Cloning, Molecular↗
PubMed1989

Differential growth in plants--a phenomenon that occurs at all levels of organization.

Differential growth is a feature of cells, the organs which they construct and the whole plant itself. The control of differential growth at each of these three levels of organization resides in the level lower than that in which it is expressed. Thus, differential growth of cells is regulated by the patterns of intracellular microtubules and cellulose microfibrils of the walls, that of organs by the pattern of growth of their cells, and that of the organism by the relative rates of organ growth. The latter is, in turn, determined an all-pervading system of correlative interactions. Plant hormones by may play a role in each of these regulatory systems.

Plant Cells↗
PubMed1991

Degradation by Streptomyces viridosporus T7A of plant material grown under elevated CO2 conditions.

The biodegradability of plant material derived from wheat grown under different concentrations of atmospheric CO2 was investigated using the lignocarbohydrate solubilising actinomycete, Streptomyces viridosporus. Growth of S. viridosporus and solubilisation of lignocarbohydrate were highest when wheat grown at ambient CO2 concentrations (350 ppm) was used as C-source. Growth of S. viridosporus and solubilisation were reduced when the plant material was derived from wheat grown at 645 ppm CO2. The results suggest that modifications in plant structure occur when wheat is grown under conditions of elevated atmospheric CO2 which make it more resistant to microbial digestion.

Biodegradation, Environmental↗
PubMed2006

Combinatorial regulation modules on GmSBP2 promoter: a distal cis-regulatory domain confines the SBP2 promoter activity to the vascular tissue in vegetative organs.

The Glycine max sucrose binding protein (GmSBP2) promoter directs phloem-specific expression of reporter genes in transgenic tobacco. Here, we identified cis-regulatory domains (CRD) that contribute with positive and negative regulation for the tissue-specific pattern of the GmSPB2 promoter. Negative regulatory elements in the distal CRD-A (-2000 to -700) sequences suppressed expression from the GmSBP2 promoter in tissues other than seed tissues and vascular tissues of vegetative organs. Deletion of this region relieved repression resulting in a constitutive promoter highly active in all tissues analyzed. Further deletions from the strong constitutive -700GmSBP2 promoter delimited several intercalating enhancer-like and repressing domains that function in a context-dependent manner. Histochemical examination revealed that the CRD-C (-445 to -367) harbors both negative and positive elements. This region abolished promoter expression in roots and in all tissues of stems except for the inner phloem. In contrast, it restores root meristem expression when fused to the -132pSBP2-GUS construct, which contains root meristem expression-repressing determinants mapped to the 44-bp CRD-G (-136 to -92). Thus, the GmSBP2 promoter is functionally organized into a proximal region with the combinatorial modular configuration of plant promoters and a distal domain, which restricts gene expression to the vascular tissues in vegetative organs.

Animals↗
PubMed2004

Arabidopsis stress-inducible gene for arginine decarboxylase AtADC2 is required for accumulation of putrescine in salt tolerance.

Arginine decarboxylase (ADC) catalyzes the first step of polyamine (PA) biosynthesis to produce putrescine (Put) from arginine (Arg). One of the 2 Arabidopsis ADC genes, AtADC2, is induced in response to salt stress causing the accumulation of free Put. To analyze the roles of stress-inducible AtADC2 gene and endogenous Put in stress tolerance, we isolated a Ds insertion mutant of AtADC2 gene (adc2-1) and characterized its phenotypes under salt stress. In the adc2-1 mutant, free Put content was reduced to about 25% of that in the control plants and did not increase under salt stress. Furthermore, the adc2-1 mutant was more sensitive to salt stress than the control plants. The stress sensitivity of adc2-1 was recovered by the addition of exogenous Put. These results indicate that endogenous Put plays an important role in salt tolerance in Arabidopsis. AtADC2 is a key gene for the production of Put under not only salinity conditions, but also normal conditions.

Acclimatization↗
PubMed2004

Symbiotic microorganisms, a key for ecological success and protection of plants.

Plant-associated microbial diversity encompasses symbionts, protecting their host against various aggressions. Mycorrhizal and rhizospheric microorganisms buffer effects of soil toxic compounds and soil-borne pathogens. Endophytic bacteria and fungi, some of which are vertically inherited through seeds, take part in plant protection by acting directly on aggressive factors (mainly pathogens and herbivores) or by enhancing plant responses. Plant protective microbial symbionts determine the ecological success of plants; they drastically modify plant communities and related trophic webs. This review suggests approaches to improve the inventory of diversity and functions of in situ plant-associated microorganisms.

Ecology↗
PubMed2004

MicroRNA regulation of NAC-domain targets is required for proper formation and separation of adjacent embryonic, vegetative, and floral organs.

BACKGROUND: MicroRNAs (miRNAs) are approximately 21 nucleotide (nt) RNAs that regulate gene expression in plants and animals. Most known plant miRNAs target transcription factors that influence cell fate determination, and biological functions of miRNA-directed regulation have been reported for four of 15 known microRNA gene families: miR172, miR159, miR165, and miR168. Here, we identify a developmental role for miR164-directed regulation of NAC-domain genes, which encode a family of transcription factors that includes CUP-SHAPED COTYLEDON1 (CUC1) and CUC2. RESULTS: Expression of a miR164-resistant version of CUC1 mRNA from the CUC1 promoter causes alterations in Arabidopsis embryonic, vegetative, and floral development, including cotyledon orientation defects, reduction of rosette leaf petioles, dramatically misshapen rosette leaves, one to four extra petals, and one or two missing sepals. Reciprocally, constitutive overexpression of miR164 recapitulates cuc1 cuc2 double mutant phenotypes, including cotyledon and floral organ fusions. miR164 overexpression also leads to phenotypes not previously observed in cuc1 cuc2 mutants, including leaf and stem fusions. These likely reflect the misregulation of other NAC-domain mRNAs, including NAC1, At5g07680, and At5g61430, for which miR164-directed cleavage products were detected. CONCLUSIONS: These results demonstrate that miR164-directed regulation of CUC1 is necessary for normal embryonic, vegetative, and floral development. They also show that proper miR164 dosage or localization is required for separation of adjacent embryonic, vegetative, and floral organs, thus implicating miR164 as a common regulatory component of the molecular circuitry that controls the separation of different developing organs and thereby exposes a posttranscriptional layer of NAC-domain gene regulation during plant development.

Amino Acid Sequence↗
PubMed2005

The endophytic fungus Trametes hirsuta as a novel alternative source of podophyllotoxin and related aryl tetralin lignans.

The aryl tetralin lignans are synthesized by Podophyllum sps. and are in great demand worldwide due to their use in synthesis of topoisomerase inhibitors. However, the sustained production of these aryl tetralin lignans requires large-scale harvesting from the natural environments, which has resulted in the plant-endangered status. In view of the difficulties in their total chemical synthesis, cultivation and failure of metabolic engineering approaches, there is a need to search for alternative sources of production of aryl tetralin lignans. We unequivocally established the methodology for isolation, identification, and characterization of a novel fungal endophyte (Trametes hirsuta) that produces aryl tetralin lignans consistently as shown by HPLC, LC-MS, LC/MS-MS and (1)H NMR. The lignans produced by the microorganism are biologically active, and exhibit potent antioxidant, anticancer and radioprotective properties. This strategy promises to improve the production of these therapeutically important compounds at lower costs.

Cell Fractionation↗
PubMed2003

Screening for acetylcholinesterase inhibitory activity in plants used in Thai traditional rejuvenating and neurotonic remedies.

Acetylcholinesterase (AChE) inhibitor has been used as a drug for the symptomatic treatment of Alzheimer's disease. In order to search for new AChE inhibitors, 32 plants used in Thai traditional rejuvenating and neurotonic remedies were collected. The plant methanolic extracts were tested for AChE inhibitory activity using Ellman's colorimetric method in 96-welled microplates. The results showed that the methanolic extracts from roots of Stephania suberosa Forman. and Tabernaemontana divaricata (L.) R.Br. ex Roem. & Schult. at concentration of 0.1 mg/ml inhibited more than 90% of AChE activity. At the same concentration, four extracts, i.e. stems of Piper interruptum Opiz., seeds of Piper nigrum L., rootbarks of Butea superba Roxb. and roots of Cassia fistula L. extracts showed 50-65% inhibitory activity on AChE. The rest of the extracts showed the AChE inhibitory activity below 50%.

Acetylcholinesterase↗
PubMed2004

In vitro antiplasmodial activity of extracts and fractions from seven medicinal plants used in the Democratic Republic of Congo.

The in vitro antiplasmodial activity of seven EtOH extracts and twenty fractions from the partition of the initial ethanolic extracts from seven African medicinal plants used in the Democratic Republic of Congo (DR Congo) for the treatment of malaria was evaluated. The most active EtOH extracts (IC50 < 3 microg/ml) were those from Cassia occidentalis leaves, Euphorbia hirta whole plant, Garcinia kola stem bark and Phyllanthus niruri whole plant. Their respective petroleum ether soluble fractions also exhibited an antiplasmodial activity with IC50 < 3 microg/ml. EtOH extracts from Vernonia amygdalina leaves (5 < IC50 < 10 microg/ml), Tetracera poggei leaves (10 < IC50 < 50 microg/ml) and Morinda morindoides leaves (50 < IC50 < 100 microg/ml) were less active, but their petroleum ether fractions exhibited a pronounced antiplasmodial activity (IC50 < 3 microg/ml). The same observation could also be made for the petroleum ether fraction from Cassia occidentalis, Euphorbia hirta, Garcinia kola and Phyllanthus niruri. Isoamyl alcohol fractions from Euphorbia hirta, Phyllanthus niruri and Vernonia amygdalina showed IC50) values less than 3 microg/ml, and from Cassia occidentalis, Garcinia kola, Morinda morindoides and Tetracera poggei between 10 and 50 microg/ml. The observed antiplasmodial activity may be related to the presence of terpenes, steroids, coumarins, flavonoids, phenolic acids, lignans, xanthones and anthraquinones.

Animals↗
PubMed2004

Screening of selected indigenous plants of Lebanon for antimicrobial activity.

The objective of this study is to test in vitro the antimicrobial efficacy of 39 water and 39 methanol extracts derived from different parts of 27 indigenous wild plant species that have been commonly used in Lebanese folk medicine. The antimicrobial efficacy was determined using the single disk diffusion method, with 10 and 20 microl load extract volume per disc. Nine test microorganisms were used namely, Escherichia coli, Proteus sp., Pseudomonas aeruginosa, Shigella dysenteria, Salmonella enteritidis, Salmonella typhi, Staphylococcus aureus, Streptococcus faecalis, and Candida albicans. Only one water extract out of 39 derived from whole plant of Alchemilla diademata showed an antimicrobial activity against Staphylococcus aureus. The percentage of test organisms that were susceptible to 10 most efficacious methanol plant extracts (20 microl/disc) were as follows: Achillea damascena whole plant (88.8%), Anthemis scariosa flower (88.8%), Cirsium sp. whole plant (88.8%), Centaurea ainetensis flowers (88.8%), Hieracium sp. whole plant (88.8%), Origanum libanoticum whole plant (99.9%), Ranunculus myosuroudes whole plant (88.8%), Nepata curviflora leaf (88.8%), Nepata curviflora stem, and Verbascum leptostychum flower (99.9%). The minimum inhibitory concentration (MIC) was determined on plant extracts that showed high efficacy against the test organisms. The chance to find antimicrobial activities was more apparent in methanol rather than water extracts of the same indigenous plants of Lebanon, with higher antimicrobial activities in 20 microl methanol extract-discs in comparison to that present in the 10 microl discs (P < 0.05).

Anti-Infective Agents↗
PubMed2004

Traditional medicine in north Côte-d'Ivoire: screening of 50 medicinal plants for antibacterial activity.

Sixty-seven crude ethanol extracts from 50 plants (31 families), which are used in North Côte-d'Ivoire as traditional remedies for bacterial diseases, were screened for in vitro activity against Gram negative (Escherichia coli and Pseudomonas aeruginosa) and Gram positive (Staphylococcus aureus, Enterococcus faecalis, Streptococcus pyogenes and Bacillus subtilis) bacteria. Thirty-one extracts showed antibacterial activity only on Gram positive bacteria. Of these, 10 extracts from 10 plant species had a promising level of activity against bacteria including strains resistant to antibiotics such as aminosides, penicillin M, macrolides, lincosamide and streptrogramin B. The most active was Erythrina senegalensis DC (Fabaceae) followed by Bobgunnia madagascariensis (Desv.) J.H. Kirkbr. & Wiersema (Caesalpinaceae), Waltheria lanceolata R. Br. ex Mast. (Sterculiaceae), Uapaca togoensis Pax. (Euphorbiaceae), Ximenia americana L. (Olacaceae), Khaya senegalensis (Ders.) A. Juss. (Meliaceae), Lannea acida A. Rich. (Anacardiaceae), Cissus populnea Guill. & Perr. (Vitaceae), Keetia hispida (Benth.) Bridson (Rubiaceae) and Ficus thonningii (Miq.) A. Rich. (Moraceae). This is the first report of the antibacterial potency of these 10 plant species on a range of bacteria. The results provided evidence that some of the studied plants might indeed be potential sources of new antibacterial agents, also against some antibiotic-resistant strains.

Anti-Bacterial Agents↗
PubMed2004

Ethnomedicine of Dharwad district in Karnataka, India--plants used in oral health care.

The present ethnomedicine survey covers the Dharwad district of Karnataka in southern India. It was revealed that 35 plants belonging to 26 families are being used to treat different types of oral ailments like toothache, plaque and caries, pyorrhea and aphthae. Sixteen of these plants were new claims for the treatment of oral ailments not previously reported in the ethnomedicinal literature of India. Basella alba, Blepharis repens, Capparis sepiaria, Oxalis corniculata and Ricinus communis are used for the treatment of aphthae; Azima tetracantha, Caesalpinia coriaria, Cleome gynandra, Gossypium herbacium, Leucas aspera, Merremia chryseides, Pergularia daemia, Prosopis juliflora and Solanum nigrum are used to treat tooth ache and Cassia hirsuta and Cassia tora are used in the treatment of plaque and caries.

Humans↗
PubMed2004

Effects of Ya-hom on the gastric secretion in rats.

The effects of Ya-hom, Thai traditional recipe, on gastric-secretory function was evaluated to verify its use for stomach discomfort treatment. The actions of Ya-hom on the gastric acid, pepsin and mucus secretions were studied in histamine- and carbachol-induced gastric fistula rats. After the first hour of collection, histamine (10 mg/kg, intramuscular injection) or carbachol (20 microg/kg, intravenous injection) were injected to stimulate gastric secretion, and water or redissolved lyophilized Ya-hom extract (0.5, 1, 2 and 4 g/kg) were intraduodenally injected. The gastric samples were collected every hour for 5 h, at the end of which, the glandular part of the stomach was assayed for the visible mucus content. Ya-hom inhibited both histamine- and carbachol-induced gastric acid, pepsin and soluble mucus secretions in a dose-dependent manner. Ya-hom had a lower maximum inhibition on the acid-stimulating effects of the histamine than that of carbachol. Ya-hom had higher maximum inhibition on the pepsin and soluble mucus-stimulating effects of histamine than that of carbachol. Ya-hom also had a higher elevated effect on histamine-induced visible mucus than that of carbachol. This study reveals that Ya-hom inhibits the stimulatory effects of histamine and carbachol on the acid, pepsin and soluble mucus secretion but potentiates the visible mucus secretion. Attenuating gastric secretion by secretagogues and increasing gastric barrier effects are parts of Ya-hom's action on stomach discomfort treatment.

Animals↗