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1.

Key message

Phylloplanins are plant-derived, antifungal glycoproteins produced by leaf trichomes. Expression of phylloplanin-GFP fusion gene to the apoplast of a blue mold susceptible tobacco resulted in increased resistance to this pathogen.

Abstract

Tobaccos and certain other plants secrete phylloplanin glycoproteins to aerial surfaces where they appear to provide first-point-of-contact resistance against fungi/fungi-like pathogens. These proteins can be collected by water washing of aerial plant surfaces, and as shown for tobacco and a sunflower phylloplanins, spraying concentrated washes onto, e.g., turf grass aerial surfaces can provide resistance against various fungi/fungi-like pathogens, in the laboratory. These results suggest that natural-product, phylloplanins may be useful as broad-selectivity fungicides. An obvious question now is can a tobacco phylloplanin gene be introduced into a disease-susceptible plant to confer endogenous resistance. Here we demonstrate that introduction of a tobacco phylloplanin gene—as a fusion with the GFP gene—targeted to the apoplasm can increase resistance to blue mold disease in a susceptible host tobacco.  相似文献   

2.
Overexpression of antifungal pathogenesis-related (PR) proteins in crop plants has the potential for enhancing resistance against fungal pathogens. Thaumatin-like proteins (TLPs) are one group (PR-5, permatins) of antifungal PR-proteins isolated from various plants. In the present study, a plasmid containing a cDNA of rice tlp (D34) under the control of the CaMV-35S promoter was introduced into tobacco plants through Agrobacterium-mediated transformation system. A considerable overproduction of TLP was observed in transformed tobacco plants by Western blot analysis. There was a large accumulation of tlp mRNA in transgenic plants as revealed by Northern blot analysis. Southern blot analysis of the DNA from transgenic tobacco plants confirmed the presence of the rice tlp gene in the genomic DNA of transgenic tobacco plants. Immunoblot analysis of intracellular and extracellular proteins of transgenic tobacco leaves using a Pinto bean TLP antibody demonstrated that the 23-kDa TLP was secreted into the extracellular matrix. T2 progeny of regenerated plants transformed with TLP gene were tested for their disease reaction to Alternaria alternata, the brown spot pathogen. Transgenic tobacco plants expressing TLP at high levels showed enhanced tolerance to necrotization caused by the pathogen. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

3.
We present a susceptibles-exposed-infectives (SEI) model to analyze the effects of seasonality on epidemics, mainly of rabies, in a wide range of wildlife species. Model parameters are cast as simple allometric functions of host body size. Via nonlinear analysis, we investigate the dynamical behavior of the disease for different levels of seasonality in the transmission rate and for different values of the pathogen basic reproduction number (R(0)) over a broad range of body sizes. While the unforced SEI model exhibits long-term epizootic cycles only for large values of R(0), the seasonal model exhibits multiyear periodicity for small values of R(0). The oscillation period predicted by the seasonal model is consistent with those observed in the field for different host species. These conclusions are not affected by alternative assumptions for the shape of seasonality or for the parameters that exhibit seasonal variations. However, the introduction of host immunity (which occurs for rabies in some species and is typical of many other wildlife diseases) significantly modifies the epidemic dynamics; in this case, multiyear cycling requires a large level of seasonal forcing. Our analysis suggests that the explicit inclusion of periodic forcing in models of wildlife disease may be crucial to correctly describe the epidemics of wildlife that live in strongly seasonal environments.  相似文献   

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Heterogeneity in the parameters governing the spread of infectious diseases is a common feature of real-world epidemics. It has been suggested that for pathogens with basic reproductive number R(0)>1, increasing heterogeneity makes extinction of disease more likely during the early rounds of transmission. The basic reproductive number R(0) of the introduced pathogen may, however, be less than 1 after the introduction, and evolutionary changes are then required for R(0) to increase to above 1 and the pathogen to emerge. In this paper, we consider how host heterogeneity influences the emergence of both non-evolving pathogens and those that must undergo adaptive changes to spread in the host population. In contrast to previous results, we find that heterogeneity does not always make extinction more likely and that if adaptation is required for emergence, the effect of host heterogeneity is relatively small. We discuss the application of these ideas to vaccination strategies.  相似文献   

6.
T-phylloplanin proteins secreted to aerial surfaces of tobacco (Nicotiana tabacum) by short procumbent trichomes inhibit spore germination and blue mold disease caused by the oomycete pathogen Peronospora tabacina. Many other plants were found to contain water-washed leaf surface proteins (phylloplanins), but the functions and properties of these are not known. Here we extend earlier evidence for the antifungal activity of T-phylloplanins using a reverse genetics approach. RNA interference of the T-phylloplanin gene in tobacco 'T.I. 1068' resulted in loss of T-phylloplanin mRNA and protein, loss of in vitro spore germination inhibition activity, and leaf infection inhibition activity of leaf water washes from RNA interference plants, and young knockdown plants were susceptible to disease. The glycoprotein character, adaxial-leaf-surface enrichment of, and renewability of T-phylloplanins are also described. We also report that leaf water washes of sunflower (Helianthus annuus) and jimson weed (Datura metel), but not soybean (Glycine max), like that of tobacco, possess ProteinaseK- and boiling-sensitive P. tabacina spore germination and tobacco leaf infection inhibition activities. Results establish that T-phylloplaninins of tobacco are active in P. tabacina inhibition, and indicate that leaf surface proteins of certain non-Nicotiana species that are not susceptible to P. tabacina disease can inhibit germination of spores of this oomycete pathogen and inhibit tobacco leaf infection by this pathogen.  相似文献   

7.
Hypersensitive response-assisting protein (HRAP) has been previously reported as an amphipathic plant protein isolated from sweet pepper that intensifies the harpin(Pss)-mediated hypersensitive response (HR). The hrap gene has no appreciable similarity to any other known sequences, and its activity can be rapidly induced by incompatible pathogen infection. To assess the function of the hrap gene in plant disease resistance, the CaMV 35S promoter was used to express sweet pepper hrap in transgenic tobacco. Compared with wild-type tobacco, transgenic tobacco plants exhibit more sensitivity to harpin(Pss) and show resistance to virulent pathogens (Pseudomonas syringae pv. tabaci and Erwinia carotovora subsp. carotovora). This disease resistance of transgenic tobacco does not originate from a constitutive HR, because endogenous level of salicylic acid and hsr203J mRNA showed similarities in transgenic and wildtype tobacco under noninfected conditions. However, following a virulent pathogen infection in hrap transgenic tobacco, hsr203J was rapidly induced and a micro-HR necrosis was visualized by trypan blue staining in the infiltration area. Consequently, we suggest that the disease resistance of transgenic plants may result from the induction of a HR by a virulent pathogen infection.  相似文献   

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植物病程相关蛋白及其在烟草中的研究进展   总被引:4,自引:0,他引:4  
植物在受到病原物侵染时,会产生一系列抗性反应,病程相关蛋白是其中参与抗病性的重要物质,能够被病原物诱导产生并在植物体内积累,对于诱导植物系统抗性,阻止病原物侵染具有重要作用。对植物病程相关蛋白的性质、诱导因素、分类和功能进行综述,并概述病程相关蛋白与烟草系统抗性的紧密联系以及烟草病程相关蛋白基因在增强系统抗性中的应用,为烟草抗病育种和病虫害防治提供了理论。  相似文献   

11.
Transgenic plants expressing the bacterio-opsin (bO) gene can spontaneously activate programmed cell death (ped) and may enhance broad-spectrum pathogen resistance by activating an intrinsic defense pathway in plant species such as tobacco and potato. In this work, we produced transgenic Rangpur lime plants with thebO gene, viaAgrobacterium tumefaciens-mediated transformation, and evaluated these plants forPhytophthora nicotianae resistance. Two transgenic lines were successfully regenerated and transformation was confirmed by GUS activity assay, PCR analysis, Southern, Northern and Western blot analyses, in addition to detecting the expressed bO protein by an immunological approach. Evaluation forPhytophthora nicotianae resistance was carried out by plant inoculations with the pathogen and quantification of the affected area. One of the two transgenic lines showed greater tolerance to the fungal pathogen as compared to the control, with significantly smaller stem lesions after pathogen challenge. This increase in pathogen tolerance is correlated with a significantly higher level of transgene expression in this line when compared with the other transgenic line. This is the first report of the introduction of a potentially important gene into Rangpur lime to provide novel pathogen tolerance.  相似文献   

12.
Hosts are armed with several lines of defence in the battle against parasites: they may prevent the establishment of infection, reduce parasite growth once infected or persevere through mechanisms that reduce the damage caused by infection, called tolerance. Studies on tolerance in animals have focused on mortality, and sterility tolerance has not been investigated experimentally. Here, we tested for genetic variation in the multiple steps of defence when the invertebrate Daphnia magna is infected with the sterilizing bacterial pathogen Pasteuria ramosa: anti-infection resistance, anti-growth resistance and the ability to tolerate sterilization once infected. When exposed to nine doses of a genetically diverse pathogen inoculum, six host genotypes varied in their average susceptibility to infection and in their parasite loads once infected. How host fecundity changed with increasing parasite loads did not vary between genotypes, indicating that there was no genetic variation for this measure of fecundity tolerance. However, genotypes differed in their level of fecundity compensation under infection, and we discuss how, by increasing host fitness without targeting parasite densities, fecundity compensation is consistent with the functional definition of tolerance. Such infection-induced life-history shifts are not traditionally considered to be part of the immune response, but may crucially reduce harm (in terms of fitness loss) caused by disease, and are a distinct source of selection on pathogens.  相似文献   

13.
Biological control of soil-borne pathogens comprises the decrease of inoculum or of the disease producing activity of a pathogen through one or more mechanisms. Interest in biological control of soil-borne plant pathogens has increased considerably in the last few decades, because it may provide control of diseases that cannot or only partly be managed by other control strategies. Recent advances in microbial and molecular techniques have significantly contributed to new insights in underlying mechanisms by which introduced bacteria function. Colonization of plant roots is an essential step for both soil-borne pathogenic and beneficial rhizobacteria. Colonization patterns showed that rhizobacteria act as biocontrol agents or as growth-promoting bacteria form microcolonies or biofilms at preferred sites of root exudation. Such microcolonies are sites for bacteria to communicate with each other (quorum sensing) and to act in a coordinated manner. Elicitation of induced systemic resistance (ISR) by plant-associated bacteria was initially demonstrated using Pseudomonas spp. and other Gram-negative bacteria. Several strains of the species Bacillus amyloliquefaciens, B. subtilis, B. pasteurii, B. cereus, B. pumilus, B. mycoides, and B. sphaericus elicit significant reductions in the incidence or severity of various diseases on a diversity of hosts. Elicitation of ISR by these strains has been demonstrated in greenhouse or field trials on tomato, bell pepper, muskmelon, watermelon, sugar beet, tobacco, Arabidopsis sp., cucumber, loblolly pine, and two tropical crops (long cayenne pepper and green kuang futsoi). Protection resulting from ISR elicited by Bacillus spp. has been reported against leaf-spotting fungal and bacterial pathogens, systemic viruses, a crown-rotting fungal pathogen, root-knot nematodes, and a stem-blight fungal pathogen as well as damping-off, blue mold, and late blight diseases. This progress will lead to a more efficient use of these strains which is worthwhile approach to explore in context of biocontrol strategies.  相似文献   

14.
The Saccharomyces cerevisiae chitinase, encoded by the CTS1-2 gene has recently been confirmed by in vitro tests to possess antifungal abilities. In this study, the CTS1-2 gene has been evaluated for its in planta antifungal activity by constitutive overexpression in tobacco plants to assess its potential to increase the plant's defence against fungal pathogens. Transgenic tobacco plants, generated by Agrobacterium-mediated transformation, showed stable integration and inheritance of the transgene. Northern blot analyses conducted on the transgenic tobacco plants confirmed transgene expression. Leaf extracts from the transgenic lines inhibited Botrytis cinerea spore germination and hyphal growth by up to 70% in a quantitative in vitro assay, leading to severe physical damage on the hyphae. Several of the F1 progeny lines were challenged with the fungal pathogen, B. cinerea, in a detached leaf infection assay, showing a decrease in susceptibility ranging from 50 to 70%. The plant lines that showed increased disease tolerance were also shown to have higher chitinase activities.  相似文献   

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The development of new strategies to enhance resistance of plants to pathogens is instrumental in preventing agricultural losses. Lesion mimic, the spontaneous formation of lesions resembling hypersensitive response lesions in the absence of a pathogen, is a dramatic phenotype occasionally induced upon expression of certain transgenes in plants. These transgenes simulate the presence of a pathogen and, therefore, activate the plant anti-pathogen defense mechanisms and induce a state of systemic resistance. Lesion mimic genes have been successfully used to enhance the resistance of a number of different plants to pathogen attack. However, constitutive expression of these genes in plants is associated with the spontaneous formation of lesions on leaves and stems, reduced growth, and lower yield. We tested the possibility of using a wound-inducible promoter to control the expression of bacterio-opsin (bO), a transgene that confers a lesion mimic phenotype in tobacco and tomato plants when constitutively expressed. We found that plants with inducible expression of bO did not develop spontaneous lesions. Nevertheless, under controlled laboratory conditions, they were found to be resistant to infection by pathogens. The activation of defense mechanisms by the bO gene was not constitutive, and occurred in response to wounding or pathogen infection. Furthermore, wounding of transgenic tobacco plants resulted in the induction of systemic resistance to pathogen attack within 48 h. Our findings provide a promising initial assessment for the use of wound-inducible promoters as a new strategy to enhance pathogen resistance in transgenic crops by means of lesion mimic genes.  相似文献   

17.
Our previous observation that host plant extracts induce production and secretion of mannitol in the tobacco pathogen Alternaria alternata suggested that, like their animal counterparts, plant pathogenic fungi might produce the reactive oxygen quencher mannitol as a means of suppressing reactive oxygen-mediated plant defenses. The concurrent discovery that pathogen attack induced mannitol dehydrogenase (MTD) expression in the non-mannitol-containing host tobacco suggested that plants, unlike animals, might be able to counter this fungal suppressive mechanism by catabolizing mannitol of fungal origin. To test this hypothesis, transgenic tobacco plants constitutively expressing a celery Mtd cDNA were produced and evaluated for potential changes in resistance to both mannitol- and non-mannitol-secreting pathogens. Constitutive expression of the MTD transgene was found to confer significantly enhanced resistance to A. alternata, but not to the non-mannitol-secreting fungal pathogen Cercospora nicotianae. These results are consistent with the hypothesis that MTD plays a role in resistance to mannitol-secreting fungal plant pathogens.  相似文献   

18.
Infectious agents in systems for producing bovine embryos might reduce the number and quality of embryos generated, result in transmission of disease to recipients and offspring, or confound findings of research. Embryo-associated pathogens might also jeopardize human health when the goal of embryo production is creating transgenic animals intended to be a source of pharmaceuticals or organs. This paper addresses risks and resulting hazards of pathogen and microbial contaminant introduction into in vivo or in vitro embryo production systems. Additionally, methods for prevention and quality control are discussed.  相似文献   

19.
A study by Gandon et al. (2001) considered the potential ways pathogens may evolve in response to vaccination with imperfect vaccines. In this paper, by focusing on acute infections of vertebrate hosts, we examine whether imperfect vaccines that do not completely block a pathogen's replication (antigrowth) or transmission (antitransmission) may lead to evolution of more or less virulent pathogen strains. To address this question, we use models of the within-host dynamics of the pathogen and the host's immune responses. One advantage of the use of this within-host approach is that vaccination can be easily incorporated in the models and the trade-offs between pathogen transmissibility, host recovery, and virulence that drive evolution of pathogens in these models can be easily estimated. We find that the use of either antigrowth or antitransmission vaccines leads to the evolution of pathogens with an increased within-host growth rate; infection of unvaccinated hosts with such evolved pathogens results in high host mortality and low pathogen transmission. Vaccination of only a fraction of hosts with antigrowth vaccines may prevent pathogens from evolving high virulence due to pathogen adaptation to unvaccinated hosts and thus protection of vaccinated hosts from pathogen-induced disease. In contrast, antitransmission vaccines may be beneficial only if they are effective enough to cause pathogen extinction. Our results suggest that particular mechanisms of action of vaccines and their efficacy are crucial in predicting longterm evolutionary consequences of the use of imperfect vaccines.  相似文献   

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