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PubMed2001

Plant--fungal interactions: the search for phytoalexins and other antifungal compounds from higher plants.

A brief review is given of some biological, chemical and chemotaxonomic aspects of phytoalexin research. Emphasis is placed on the search for antifungal compounds in the plant families Leguminosae and Rosaceae, and in rice, Oryza sativa. The possible role of phytoalexins in the resistance of rice plants against the fungus Pyricularia oryzae (= Magnaporthe grisea) is discussed, and the future prospects of phytoalexin research are outlined.

Antifungal Agents↗
PubMed2004

Apoptosis in plants: specific features of plant apoptotic cells and effect of various factors and agents.

Apoptosis is an integral part of plant ontogenesis; it is controlled by cellular oxidative status, phytohormones, and DNA methylation. In wheat plants apoptosis appears at early stages of development in coleoptile and initial leaf of 5- to 6-day-old seedlings. Distinct ultrastructural features of apoptosis observed are (1). compaction and vacuolization of cytoplasm in the apoptotic cell, (2). specific fragmentation of cytoplasm and appearance in the vacuole of unique single-membrane vesicles containing active organelles, (3). cessation of nuclear DNA synthesis, (4). condensation and margination of chromatin in the nucleus, (5). internucleosomal fragmentation of nuclear DNA, and (6). intensive synthesis of mitochondrial DNA in vacuolar vesicles. Peroxides, abscisic acid, ethylene releaser ethrel, and DNA methylation inhibitor 5-azacytidine induce and stimulate apoptosis. Modulation of the reactive oxygen species (ROS) level in seedling by antioxidants and peroxides results in tissue-specific changes in the target date for the appearance and the intensity of apoptosis. Antioxidant butylated hydroxytoluene (BHT) reduces the amount of ROS and prevents apoptosis in etiolated seedlings, prolongs coleoptile life span, and prevents the appearance of all apoptotic features mentioned. Besides, BHT induces large structural changes in the organization of all cellular organelles and the formation of new unusual membrane structures in the cytoplasm. BHT distorts mitosis and this results in the appearance of multiblade polyploid nuclei and multinuclear cells. In roots of etiolated wheat seedlings, BHT induces differentiation of plastids with the formation of chloro(chromo)plasts. Therefore, ROS controlled by BHT seems to regulate mitosis, trigger apoptosis, and control plastid differentiation and the organization of various cellular structures formed by endocytoplasmic reticulum.

Antioxidants↗
PubMed1996

The oxidative burst protects plants against pathogen attack: mechanism and role as an emergency signal for plant bio-defence--a review.

Various aspects, mechanisms and functions of the oxidative burst with generation of O2- superoxide anions in plant cells, which is stimulated by active defence-inducing agents such as fungal infection or elicitor treatment, were reviewed mainly on the basis of experimental evidence obtained in a system of Solanaceae plants and Phytophthora spp. The oxidative burst may be due to an O(2-)generating NADPH oxidase in the plasma membrane, which is activated with combinations of cytosolic proteins, Ca2+, calmodulin and protein kinase, following stimulation by elicitor molecules. The oxidative burst may play the role of an internal emergency signal for induction of the metabolic cascade for active defence.

Cells, Cultured↗
PubMed1975

Hydrolysis of plant cuticle by plant pathogens. Purification, amino acid composition, and molecular weight of two isozymes of cutinase and a nonspecific esterase from Fusarium solani f. pisi.

The extracellular fluid of the plant pathogen, Fusarium solani f. pisi, grown on the plant cuticular polymer, cutin, was shown to contain cutinase and p-nitrophenyl palmitate hydrolase activities (R.E. Purdy and P.E. Kolattukudy (1973), Arch. Biochem. Biophys. 159, 61). From this extracellular fluid two isozymes of cutinase and a nonspecific esterase (p-nitrophenyl palmitate hydrolase) were isolated using Sephedex G-100 gel filtration, QAE-Sephadex chromatography, and SE-Sephedex chromatography. Phenolics contained in the extracellular fluid were found to be associated with the cutinase but not with the nonspecific esterase, and the phenolic materials were removed from cutinase at the QAE-Sephedex step. A 34-fold purification of the nonspecific esterase and a 6.5-fold purification of cutinase were achieved by the procedure described. The two isozymes of cutinase (I and II) and the nonspecific esterase were homogeneous as judged by polyacrylamide disc gel electrophoresis and sedimentation equilibrium centrifugation. Molecular weights of cutinase I, cutinase II, and the nonspecific esterase were determined by Sephedex G-100 gel filtration, sedimentation equilibrium centrifugation, amino acid composition, and sodium dodecyl sulfate polyacrylamide disc gel electrophoresis. The values obtained with these techniques agreed with each other and were about 22,000 for both cutinases and 52,000 for the nonspecific esterase. The dodecyl sulfate gel electrophoresis indicated that a small portion of cutinase II contained proteolylic clips, near the middle of the polypeptide chain, and that the nonspecific esterase might also have undergone some proteolylic modification. The amino acid composition of cutinase I was similar to that of cutinase II except for the presence of a larger number of tryptophan residues in the latter, while the amino acid composition of the nonspecific esterase showed more differences from that of either cutinase.

Amino Acids↗
PubMed2003

Simple detection method of powerful antiradical compounds in the raw extract of plants and its application for the identification of antiradical plant constituents.

A simple detection method for a powerful radical scavenging compound in a mixture containing a large variety of compounds, such as the raw extract of edible plants, was developed using 1,1-diphenyl-2-picrylhydrazyl (DPPH) as the radical reagent. The method was established on the basis of the features of the typical chain-breaking antioxidation reaction mechanism, which suggests that the radical scavenging antioxidant should be converted to other stable nonradical compounds during the reaction. This method requires only a simple HPLC instrument, and the disappearance or decrease in the peak intensity, which is induced by the addition of DPPH. This change is monitored by the HPLC to detect the powerful radical scavenger from the complex mixture. The method was applied to the detection and identification of the most powerful antiradical compound in the extracts of three antioxidatively active plant extracts (Psidium guajava, Citrus depressa, and Hypericum chinense). The radical scavenging efficiency of a newly identified compound from H. chinense was also compared with that of Trolox and catechin using the method.

Antioxidants↗
PubMedDate not supplied

Toxicants from mangrove plants, VI. Heritonin, a new piscicide from th mangrove plant Heritiera littoralis.

The mangrove plant Heritiera littoralis has been utilized by natives of the Philippines as a fish poison. The petroleum ether extract of this plant has shown toxicity to fish (Tilapia nilotica). A new piscicide, which was assigned the name heritonin [1], has been identified as one of the compounds with ichthyotoxicity. The structure was elucidated by spectroscopic methods.

Animals↗
PubMedDate not supplied

A simplified plaque reduction assay for antiviral agents from plants. Demonstration of frequent occurrence of antiviral activity in higher plants.

An improved plaque reduction assay for antiviral activity was developed and used to examine extracts from sixty-one higher plants. Substantial antiviral activity was observed in ca. 20%, which is higher than might be expected given the limited metabolic differences between viruses and their hosts. The frequent antiviral activity may represent phytoalexins elaborated to protect against plant viruses.

Antiviral Agents↗
PubMed2001

NtSET1, a member of a newly identified subgroup of plant SET-domain-containing proteins, is chromatin-associated and its ectopic overexpression inhibits tobacco plant growth.

The SET- and chromo-domains are recognized as signature motifs for proteins that contribute to epigenetic control of gene expression through effects on the regional organization of chromatin structure. This paper reports the identification of a novel subgroup of SET-domain-containing proteins in tobacco and Arabidopsis, which show highest homologies with the Drosophila position-effect-variegation repressor protein SU(VAR)3-9 and the yeast centromer silencing protein CLR4. The tobacco SET-domain-containing protein (NtSET1) was fused to the green fluorescence protein (GFP) that serves as a visual marker for localization of the recombinant protein in living cells. Whereas control GFP protein alone was uniformly dispersed within the nucleus and cytoplasm, the NtSET1-GFP fusion protein showed a non-uniform localization to multiple nuclear regions in interphase tobacco TBY2 cells. During mitosis, the NtSET1-GFP associated with condensed chromosomes with a non-random distribution. The NtSET1 thus appears to have distinct target regions in the plant chromatin. Overexpression of the NtSET1-GFP in transgenic tobacco inhibited plant growth, implicating the possible involvement of the NtSET1 in transcriptional repression of growth control genes through the formation of higher-order chromatin domains.

Amino Acid Sequence↗
PubMed2000

Diseases of plants transmissible between plants and man (Phytonoses) exist--follow-up paper.

The purpose of this paper is to revise the original paper by qualifying a statement made therein and making two sections more inclusive. The qualification is the insertion of the word 'adult' before the word 'volunteers' in one sentence. The scope of the first section is increased by: (i) drawing attention to the possibility that besides other organisms (i.e. non-mycoplasma-like organisms (non-MLOs)) and viruses that could be inadvertently transmitted between members of the plant and animal kingdoms, other infectious entities including viroids and prions and/or prion-like elements should also be considered in this regard; and (ii) the need to consider the possible transmission of either antibiotic-resistant MLOs and/or MLOs harbouring entities that are either naturally infectious and pathogenic for man or may opportunistically infect man. The scope of the second section is increased by proposing additional possible mechanisms of transmission of MLOs between plants and man.

Animals↗
PubMed1998

MP2C, a plant protein phosphatase 2C, functions as a negative regulator of mitogen-activated protein kinase pathways in yeast and plants.

By interference of the yeast pheromone mitogen-activated protein kinase (MAPK) pathway with an alfalfa cDNA expression library, we have isolated the MP2C gene encoding a functional protein phosphatase type 2C. Epistasis analysis in yeast indicated that the molecular target of the MP2C phosphatase is Ste11, a MAPK kinase kinase that is a central regulator of the pheromone and osmosensing pathways. In plants, MP2C functions as a negative regulator of the stress-activated MAPK (SAMK) pathway that is activated by cold, drought, touch, and wounding. Although activation of the SAMK pathway occurs by a posttranslational mechanism, de novo transcription and translation of protein factor(s) are necessary for its inactivation. MP2C is likely to be this or one of these factors, because wound-induced activation of SAMK is followed by MP2C gene expression and recombinant glutathione S-transferase-MP2C is able to inactivate extracts containing wound-induced SAMK. Wound-induced MP2C expression is a transient event and correlates with the refractory period, i.e., the time when restimulation of the SAMK pathway is not possible by a second stimulation. These data suggest that MP2C is part of a negative feedback mechanism that is responsible for resetting the SAMK cascade in plants.

Amino Acid Sequence↗
PubMed2003

Micronutrient fortification of plants through plant breeding: can it improve nutrition in man at low cost?

Can commonly-eaten food staple crops be developed that fortify their seeds with essential minerals and vitamins? Can farmers be induced to grow such varieties? If so, would this result in a marked improvement in human nutrition at a lower cost than existing nutrition interventions? An interdisciplinary international effort is underway to breed for mineral- and vitamin-dense varieties of rice, wheat, maize, beans and cassava for release to farmers in developing countries. The biofortification strategy seeks to take advantage of the consistent daily consumption of large amounts of food staples by all family members, including women and children as they are most at risk for micronutrient malnutrition. As a consequence of the predominance of food staples in the diets of the poor, this strategy implicitly targets low-income households. After the one-time investment is made to develop seeds that fortify themselves, recurrent costs are low and germplasm may be shared internationally. It is this multiplier aspect of plant breeding across time and distance that makes it so cost-effective. Once in place, the biofortified crop system is highly sustainable. Nutritionally-improved varieties will continue to be grown and consumed year after year, even if government attention and international funding for micronutrient issues fades. Biofortification provides a truly feasible means of reaching malnourished populations in relatively remote rural areas, delivering naturally-fortified foods to population groups with limited access to commercially-marketed fortified foods that are more readily available in urban areas. Biofortification and commercial fortification are, therefore, highly complementary. Breeding for higher trace mineral density in seeds will not incur a yield penalty. Mineral-packed seeds sell themselves to farmers because, as recent research has shown, these trace minerals are essential in helping plants resist disease and other environmental stresses. More seedlings survive and initial growth is more rapid. Ultimately, yields are higher, particularly in trace mineral-'deficient' soils in arid regions.

Biological Availability↗
PubMed2000

pH, abscisic acid and the integration of metabolism in plants under stressed and non-stressed conditions: cellular responses to stress and their implication for plant water relations.

A paradigm for the response of plants to stress is presented which suggests that plants move towards a state of minimal metabolic activity as a stress intensifies and remain in that state until that stress is relieved. The paradigm is based on the proposition that cells that interface with the transpiration stream employ variations on the following theme to move towards that state. Tension on the apoplastic water opens a mechanosensitive Ca2+ channel, a response that is augmented by apoplastic ABA. The resulting elevated cytoplasmic Ca2+ deactivates a plasmalemma H+/ATPase and also activates a K(+)-H+ symport. The inflow of K+ and H+ depolarizes the membrane and renders the apoplast less acidic, the protons being removed to the vacuole and the K+ ions being re-exported via the K+ outward rectifying channel. The onset of darkness in guard and mesophyll cells deactivates the plasmalemma H+/ATPase and then the events outlined above ensue except that these cells do not appear to utilize either Ca2+ or ABA during these changes. In stressed cells it is proposed that elevated cytoplasmic Ca2+ activates the release of an ABA precursor from a stored form. ABA is then released in the apoplast after export of the precursor if the activity of the K(+)-H+ symport has brought the apoplastic pH close to 7.0. It is proposed that aquaporins in the xylem parenchyma and mesophyll cells are opened by elevated cytoplasmic Ca2+ when the water potential of the transpiration stream is high so that water can be stored in the 'xylem parenchyma reservoir'. The water in this reservoir is then used to increase the water potential in the transpiration stream when the water column is under tension and to help repair embolisms by a mechanism that resembles stomatal closure.

Abscisic Acid↗
PubMed1986

Light regulation of a SSRubisco-nos chimaeric gene: photoregulatory control sequences from a C3 plant function in cells of a CAM plant.

A SSRubisco-nos chimaeric gene has been constructed, in an oncogenic Ti-plasmid vector. A 900bp soybean SSRubisco upstream fragment, carrying CAAT and TATA boxes and transcription initiation point, was fused to the nos coding region, the fusion site being within the 5'-untranslated region. When this chimaeric construct was transferred to Kalanchoe cells, nos expression was shown to be light-regulated. Thus DNA sequences responsible for light-dark control of gene expression are wholly or partly contained within the 900bp soybean SSRubisco upstream region. Moreover, this is the first demonstration that photoregulatory elements in a gene derived from a C3 plant, function in cells of a plant exhibiting the CAM trait.

Base Sequence↗
PubMed2004

Positioning Arabidopsis in plant biology. A key step toward unification of plant research.

One of the major challenges in biological investigation involves developing a robust predictive framework in which biological outputs can be predicted from input data and knowledge of the state of the system. Currently, genomics-based strategies provide a strong framework for integrating biological knowledge within a species and linking knowledge between diverse organisms, as DNA sequence is a durable, accurate, and complete record of biological information. As such, it provides the best source of information upon which predictive rules can start to be built, tested, and generalized. Generalization is a key component of predictive biology because it defines the extent to which we can accurately predict from one instance to another. In plant science, several important research themes are concerned with generalization, and progress in these areas is reviewed here. The importance of developing a framework for predictive biology that includes a much wider variety of plant species is also emphasized.

Arabidopsis↗
PubMed1990

The influence of selected tannin-containing plant species on the tenacity of pathogenic bacteria in an in-vitro rumen system. 1. Communication: the influence of selected plant species on the tenacity of Cl. perfringens.

The effect of plant species containing tannins on the tenacity of Cl. perfringens was elucidated. Trials were purchased in physiological saline solution and in a rumen-fluid-medium under anaerobic conditions. The results obtained show, that within minutes the tenacity of Cl. perfringens can be reduced by some of the tested plant material not only in physiological saline solution but also in a rumen-fluid-medium. The results indicate that the reaction of some vegetable tannins and Clostridium perfringens germs is a specific one and could be used in controlling diseases caused by Clostridium perfringens.

Acacia↗
PubMed2026

Complete genome sequence of Bacillus subtilis strain S-LA1, a potential plant probiotic endophyte from the medicinal plant Leucas aspera.

Bacillus subtilis strain S-LA1 is an endophytic bacterium isolated from Leucas aspera roots that harbors a 4.2 Mbp genome predicted to encode several traits for nutrient acquisition, plant growth promotion, and plant probiotic efficacy. Genomic characterization underscores its potential as a microbial resource supporting sustainable agriculture and crop disease management strategies.

Bacillus↗
PubMed1986

Evidence that the amino acid composition of the particle proteins of plant viruses is characteristic of the virus group. II. Discriminant analysis according to structural biological and classification properties of plant viruses.

The amino acid composition (AAC) of the coat proteins (CPs) of 126 plant viruses or strains were analyzed by stepwise discriminant analysis. The criteria chosen for discrimination were: the structure of virus particles (3 clusters); the mode of of transmission of the viruses (6 clusters); and the grouping of viruses according to the classification of the International Committee on Taxonomy of Viruses (23 groups). Statistically significant correlations were obtained with different groups of discriminant amino acids. The results confirm that the AAC of the CPs contains all the information needed for a quantitative classification of plant viruses. These results and possible explanations of these clustering patterns are discussed.

Amino Acids↗
PubMed2005

Plant genotoxicity: a molecular cytogenetic approach in plant bioassays.

It is important for the prevention of DNA changes caused by environment to understand the biological consequences of DNA damages and their molecular modes of action that lead to repair or alterations of the genetic material. Numerous genotoxicity assay systems have been developed to identify DNA reactive compounds. The available data show that plant bioassays are important tests in the detection of genotoxic contamination in the environment and the establishment of controlling systems. Plant system can detect a wide range of genetic damage, including gene mutations and chromosome aberrations. Recently introduced molecular cytogenetic methods allow analysis of genotoxicity, both at the chromosomal and DNA level. FISH gives a new possibility of the detection and analysis of chromosomal rearrangements in a great detail. DNA fragmentation can be estimated using the TUNEL test and the single cell gel electrophoresis (Comet assay).

Biological Assay↗