摘要 :
Peptides with antimicrobial properties are present in most if not all plant species. All plant antimicrobial peptides isolated so far contain even numbers of cysteines (4, 6, or 8), which are all pairwise connected by disulfide br...
展开
Peptides with antimicrobial properties are present in most if not all plant species. All plant antimicrobial peptides isolated so far contain even numbers of cysteines (4, 6, or 8), which are all pairwise connected by disulfide bridges, thus providing high stability to the peptides. Based on homologies at the primary structure level, plant antimicrobial peptides can be classified into distinct families including thionins, plant defensins, lipid transfer proteins, and hevein- and knottin-type antimicrobial peptides. Detailed three-dimensional structure information has been obtained for one or more members of these peptide families. All antimicrobial peptides studied thus far appear to exert their antimicrobial effect at the level of the plasma membrane of the target microorganism, but the different peptide types are likely to act via different mechanisms. Antimicrobial peptides can occur in all plant organs. In unstressed organs, antimicrobial peptides are usually most abundant in the outer cell layer lining the organ, which is consistent with a role for the antimicrobial peptides in constitutive host defense against microbial invaders attacking from the outside. Thionins are predominantly located intracellularly but are also found in the extracellular space, whereas most plant defensins and lipid transfer proteins are deposited exclusively in the extracellular space. In a number of plant species, a strong induction of genes expressing either thionins, plant defensins, or lipid transfer proteins has been observed on infection of the leaves by microbial pathogens. Hence, antimicrobial peptides can also take part in the inducible defense response of plants. Constitutive expression in transgenic plants of heterologous antimicrobial peptide genes has been achieved, which in some cases has led to enhanced resistance to particular microbial plant pathogens.
收起
摘要 :
Wheat bran extract (WBE) is a food-grade preparation that is highly enriched in arabinoxylan-oligosaccharides. As part of the safety evaluation of WBE, its genotoxic potential was assessed in a bacterial reverse mutagenicity assay...
展开
Wheat bran extract (WBE) is a food-grade preparation that is highly enriched in arabinoxylan-oligosaccharides. As part of the safety evaluation of WBE, its genotoxic potential was assessed in a bacterial reverse mutagenicity assay (Ames test) and a chromosome aberration assay on Chinese hamster lung fibroblast cells. These in vitro genotoxicity assays showed no evidence of mutagenic or clastogenic activity with WBE. The safety of WBE was furthermore evaluated in a subchronic toxicity study on rats that were fed a semisynthetic diet (AIN 93G) containing 0.3%, 1.5%, or 7.5% WBE for 13 weeks, corresponding to an average intake of 0.2, 0.9, and 4.4 g/kg body weight (bw) per day, with control groups receiving the unsupplemented AIN 93G, AIN 93G with 7.5% inulin, or AIN 93G with 7.5% wheat bran. Based on this rat-feeding study, the no-observed-adverse-effect level (NOAEL) for WBE was determined as 4.4 g/kg (bw)/d, the highest dose tested.
收起
摘要 :
Wheat bran extract (WBE) is a food-grade preparation that is highly enriched in arabinoxylan-oligosaccharides. As part of the safety evaluation of WBE, its genotoxic potential was assessed in a bacterial reverse mutagenicity assay...
展开
Wheat bran extract (WBE) is a food-grade preparation that is highly enriched in arabinoxylan-oligosaccharides. As part of the safety evaluation of WBE, its genotoxic potential was assessed in a bacterial reverse mutagenicity assay (Ames test) and a chromosome aberration assay on Chinese hamster lung fibroblast cells. These in vitro genotoxicity assays showed no evidence of mutagenic or clastogenic activity with WBE. The safety of WBE was furthermore evaluated in a subchronic toxicity study on rats that were fed a semisynthetic diet (AIN 93G) containing 0.3%, 1.5%, or 7.5% WBE for 13 weeks, corresponding to an average intake of 0.2, 0.9, and 4.4 g/kg body weight (bw) per day, with control groups receiving the unsupplemented AIN 93G, AIN 93G with 7.5% inulin, or AIN 93G with 7.5% wheat bran. Based on this rat-feeding study, the no-observed-adverse-effect level (NOAEL) for WBE was determined as 4.4 g/kg (bw)/d, the highest dose tested.
收起
摘要 :
The introduction and expression of several transgenes is frequently required in either basic or applied studies in plant biotechnology. For instance, the expression of polygenic agronomic characteristics in plants or the manipulat...
展开
The introduction and expression of several transgenes is frequently required in either basic or applied studies in plant biotechnology. For instance, the expression of polygenic agronomic characteristics in plants or the manipulation of complex biosynthetic pathways requires introduction of multiple transgenes into the plant genome. Hence, full exploitation of the potential for manipulating plant metabolism awaits the development and adoption of methods for the routine introduction or manipulation of multiple transgenes. This review describes the generation of plants with multiple transgenes and summarizes our current understanding of the different approaches for obtaining these transgenic plants.
收起
摘要 :
In wheat endosperm, the main isoforms of puroindolines (PIN-a and PIN-b) and non-specific lipid transfer protein (ns-LTP1e1), structurally related lipid binding proteins were asynchronously synthesized during maturation and partia...
展开
In wheat endosperm, the main isoforms of puroindolines (PIN-a and PIN-b) and non-specific lipid transfer protein (ns-LTP1e1), structurally related lipid binding proteins were asynchronously synthesized during maturation and partially degraded duringgermination. These proteins were not detected in roots and hypocotyls of seedlings, while ns-LTP1e1, but not PINs, was synthesized during germination in the scutellum and/or mesocotyl. In mature wheat seeds, ns-LTP1-e1 was specifically localised withinaleurone cells but not in cell walls in marked contrast with most other plant ns-LTP1s. PINs are both located in the starchy endosperm and in the aleurone layer. In the latter cells, PINs and ns-LTP1-e1 were both localised in small inclusions within protein-rich aleurone grains. In the mature starchy endosperm, PINs were localised in the protein matrix and at the interface between starch granules and protein matrix. It was shown that both PIN-a and PIN-b, have antifungal properties in vitro, and a synergistic enhancement of the antifungal properties of alpha-purothionins (alpha-PTH) was observed in the presence of PINs. This synergism could have biological significance since alpha-PTH and PINs are both located in the protein matrix of starchy endosperm. ns-LTP1e1 was not capable to inhibit growth of fungi and a synergy rather weak in comparison with PINs was also observed between ns-LTP1e1 and alpha-PTH.
收起
摘要 :
Kip-related proteins (KRPs) play a major role in the regulation of the plant cell cycle. We report the identification of five putative rice (Oryza sativa) proteins that share characteristic motifs with previously described plant K...
展开
Kip-related proteins (KRPs) play a major role in the regulation of the plant cell cycle. We report the identification of five putative rice (Oryza sativa) proteins that share characteristic motifs with previously described plant KRPs. To investigate the function of KRPs in rice development, we generated transgenic plants overexpressing the Orysa;KRP1 gene. Phenotypic analysis revealed that overexpressed KRP1 reduced cell production during leaf development. The reduced cell production in the leaf meristem was partly compensated by an increased cell size, demonstrating the existence of a compensatory mechanism in monocot species by which growth rate is less reduced than cell production, through cell expansion. Furthermore, Orysa;KRP1 overexpression dramatically reduced seed filling. Sectioning through the overexpressed KRP1 seeds showed that KRP overproduction disturbed the production of endosperm cells. The decrease in the number of fully formed seeds was accompanied by a drop in the endoreduplication of endosperm cells, pointing toward a role of KRP1 in connecting endocycle with endosperm development. Also, spatial and temporal transcript detection in developing seeds suggests that Orysa;KRP1 plays an important role in the exit from the mitotic cell cycle during rice grain formation.
收起
摘要 :
The PDF1.2 gene of Arabidopsis thaliana encodes a plant defensin that is systemically induced by a SA-independent signalling pathway. Traditionally, tobacco has been used to analyse pathogen-induced systemic responses. To determin...
展开
The PDF1.2 gene of Arabidopsis thaliana encodes a plant defensin that is systemically induced by a SA-independent signalling pathway. Traditionally, tobacco has been used to analyse pathogen-induced systemic responses. To determine whether a similarsystemic signalling pathway exists in tobacco, the promoter region of the PDF1.2 gene was fused to the uidA reporter gene encoding beta-glucuronidase (GUS) and introduced into tobacco (cv. Xanthi-nc NN). The transgenic tobacco plants showed no increasein GUS activity after treatment with salicylate but treatment of seedlings and mature leaves with jasmonic acid, methyl viologen and rose bengal led to an induction of GUS activity, with jasmonic acid being the strongest inducer. Exposure of mature transgenic plants to ethylene also led to a significant induction of GUS. Wounding resulted in highly localised induction at wound sites. Inoculation of leaves with the compatible pathogens Phytophthora parasitica var. nicotianae [Phytophthora nicotianae var.parasitica], Cercospora nicotianae and the incompatible tobacco mosaic tobamovirus (TMV) all led to strong GUS induction. The systemic signalling of the PDF1.2 promoter was investigated by either inoculation of a lower leaf with TMV or treatment of thisleaf with jasmonic acid. Increased GUS activity was observed in the non-inoculated upper leaves at 4-6 days after treatment. Treatment of the plants with TMV induced GUS mRNA and PR1a mRNA locally and systemically while jasmonic acid treatment induced GUS mRNA only. These results are consistent with the existence of a pathogen-induced, salicylate-independent systemic signalling pathway, possibly involving ethylene and jasmonate signalling components, in both tobacco and Arabidopsis.
收起
摘要 :
We have constructed a binary vector for Agrobacterium-mediated plant transformation, which has a multiple cloning site consisting of 13 hexanucleotide restriction sites, 6 octanucleotide restriction sites and 5 homing endonuclease...
展开
We have constructed a binary vector for Agrobacterium-mediated plant transformation, which has a multiple cloning site consisting of 13 hexanucleotide restriction sites, 6 octanucleotide restriction sites and 5 homing endonuclease sites. The homing endonuclease sites have the advantages to be extremely rare in natural sequences and to allow unidirectional cloning. We have also constructed a set of auxiliary vectors allowing the assembly of expression cassettes flanked by homing endonuclease sites. The expression cassettes assembled in these auxiliary vectors can be transferred into the binary vector with virtually no risk of cutting the vector within previously introduced sequences. This vector set is ideally suited for the construction of plant transformation vectors containing multiple expression cassettes and/or other elements such as matrix attachment regions. With this modular vector system, six different expression units were constructed in as many auxiliary vectors and assembled together in one plant transformation vector. The transgenic nature of Arabidopsis thaliana plants, transformed with this plant transformation vector, was assessed and the expression of each of the six genes was demonstrated. [References: 41]
收起
摘要 :
Rs-AFPs are antifungal proteins, isolated from radish (Raphanus sativus) seed or leaves, which consist of 50 or 51 amino acids and belong to the plant defensin family of proteins. Four highly homologous Rs-AFPs have been isolated ...
展开
Rs-AFPs are antifungal proteins, isolated from radish (Raphanus sativus) seed or leaves, which consist of 50 or 51 amino acids and belong to the plant defensin family of proteins. Four highly homologous Rs-AFPs have been isolated (Rs-AFP1-4). The structure of Rs-AFP1 consists of three beta-strands and an alpha-helix, and is stabilized by four cystine bridges. Small peptides deduced from the native sequence, still having biological activity, are not only important tools to study structure-function relationships, but may also constitute a commercially interesting target. In an earlier study, we showed that the antifungal activity of Rs-AFP2 is concentrated mainly in the beta2-beta3 loop. In this study, we synthesized linear 19-mer peptides, spanning the entire beta2-beta3 loop, that were found to be almost as potent as Rs-AFP2. Cysteines, highly conserved in the native protein, are essential for maintaining the secondary structure of the protein. Surprisingly, in the 19-mer loop peptides, cysteines can be replaced by alpha-aminobutyric acid, which even improves the antifungal potency of the peptides. Analogous cyclic 19-mer peptides, forced to adopt a hairpin structure by the introduction of one or two non-native disulfide bridges, were also found to possess high antifungal activity. The synthetic 19-mer peptides, like Rs-AFP2 itself, cause increased Ca2+ influx in pregerminated fungal hyphae.
收起
摘要 :
Inoculation of wild-type Arabidopsis plants with the fungus Alternaria brassicicola results in systemic induction of genes encoding a plant defensin (PDF1.2), a basic chitinase (PR-3), and an acidic hevein-like protein (PR-4). Pat...
展开
Inoculation of wild-type Arabidopsis plants with the fungus Alternaria brassicicola results in systemic induction of genes encoding a plant defensin (PDF1.2), a basic chitinase (PR-3), and an acidic hevein-like protein (PR-4). Pathogen-induced induction of these three genes is almost completely abolished in the ethylene-insensitive Arabidopsis mutant ein2-1. This indicates that a functional ethylene signal transduction component (EIN2) is required in this response. The ein2-1 mutants were found to be markedly more susceptible than wild-type plants to infection by two different strains of the gray mold fungus Botrytis cinerea. In contrast, no increased fungal colonization of ein2-1 mutants was observed after challenge with avirulent strains of either Peronospora parasitica or A. brassicicola. Our data support the conclusion that ethylene-controlled responses play a role in resistance of Arabidopsis to some but not all types of pathogens.
收起
原文获取