Monoclonal antibodies to cell surface components of zoospores and cysts of the fungusPythium aphanidermatum reveal species-specific antigens

Stimulation and Isolation of Paraphysoderma sedebokerense (Blastocladiomycota) Propagules and Their Infection Capacity Toward Their Host Under Different Physiological and Environmental Conditions

Paraphysoderma sedebokerense (P. sedebokerense) (Blastocladiomycota) is a facultative pathogenic chytrid that causes irreversible damage to some green microalgae. Specific attacks leading to culture collapse under different conditions have only been described in the lucrative microalga Haematococcus pluvialis (H. pluvialis), while generating biomass for ketocarotenoid astaxanthin production, both indoors and outdoors. In order to manage the infection, parasite propagules (zoospores/amoeboid swarmers), the initiators of the disease, must be studied. Until now, no report on isolated P. sedebokerense propagules has been published. Here, we report on a reproducible method for the stimulation of P. sedebokerense propagule release and their isolation from fungal cultures in synthetic media and infected H. pluvialis cultures, and we further studied their development under different conditions. The isolated propagules featured different spore morphotypes, with coatless spherical spores and amoeboid swarmers being the most dominant in the first pulse of propagule release in both cultures. Inoculating the pure propagules with the host, in both the presence and absence of nitrogen, resulted in epidemic development in both green and red cells; however, in red cells, the epidemic developed more quickly in the presence of nitrogen. Biologically non-active autoclaved host cells were used to distinguish the initial stages of recognition from more progressive stages of the epidemics; on these cells, propagules encysted but did not develop further. These results prove the existence of heat-stable recognition sites on the host and an obligatory signal transduction from the host to support fungal cyst development. The propagule isolation method described herein is a breakthrough that will enable researchers to study the influence of different substances on the propagules, specifically as the initiators of the infection, and thus assist in the management of chytrid diseases. Moreover, it will be useful in studying host-parasite recognition and, therefore, will increase our understanding of the multiple chytrid infections found in nature.

Detection of Tilletia controversa using immunofluorescent monoclonal antibodies

AIMS

Tilletia controversa is an internationally quarantined pathogenic fungus that causes dwarf bunt of wheat and is similar to Tilletia caries in both teliospore morphology and genetic structure. This study developed a rapid and sensitive immunofluorescence method for differentiating the teliospores of T. controversa from T. caries.

METHODS AND RESULTS

The method utilizes monoclonal antibody D-1 against teliospores of T. controversa as well as a PE-Cy3-conjugated goat anti-mouse antibody (overlapping light excitation of 495 and 555 nm). The orange cycle fluorescent signal was stronger against T. controversa teliospores in the outer spore wall and net ridge, whereas only the green signal was observed for the protoplasm of T. caries teliospores. The detection limit of this method was 2.0 μg ml(-1) of the D-1 monoclonal antibody.

CONCLUSION

This study describes the production and diagnostic application of a novel mouse monoclonal antibody specific to T. controversa teliospores.

SIGNIFICANCE AND IMPACT OF THE STUDY

This method could be used for the on-site identification of T. controversa teliospores in the near future and will help in selecting fungicides to control dwarf bunt of wheat as further technical developments are achieved.

An immunofluorescence assay for the detection of wheat rust species using monoclonal antibody against urediniospores of Puccinia triticina

AIMS

Wheat (Triticum aestivum) is one of the most important crop species, but yields are often drastically reduced by rust epidemics. In this report, we describe a rapid and sensitive immunofluorescence method for the detection of urediniospores of the fungi Puccinia striiformis f. sp. tritici, Puccinia triticina and Puccinia graminis f. sp. tritici, which are causal agents of wheat rust.

METHODS AND RESULTS

The method uses monoclonal antibody LPT-2 against the urediniospores of P. triticina and PE-cy3 goat anti-mouse. Urediniospores of P. triticina or those of two species that are difficult to distinguish from P. triticina, P. striiformis f. sp. tritici or P. graminis f. sp. tritici were immobilized on a glass slide, and the sample was then treated with LPT-2. Thereafter, a second antibody, goat anti-mouse conjugated PE-cy3, was added, and the slide was observed in a fluoroscope. The fluorescent signal was strong with P. triticina urediniospores, weak with P. striiformis f. sp. tritici urediniospores and weak-to-intermediate with P. graminis f. sp. tritici urediniospores. The detection limit of this method was 2 ng ml(-1) of the monoclonal antibody LPT-2.

CONCLUSIONS

In this article, we describe the production and diagnostic application of a novel mouse monoclonal antibody specific to urediniospores of P. triticina.

SIGNIFICANCE AND IMPACT OF THE STUDY

After further technical development, this method may become a tool for on-site identification of P. triticina urediniospores and will therefore help in the selection and timing of fungicide applications for control of wheat rust outbreaks.

Immunodetection of fungal and oomycete pathogens: established and emerging threats to human health, animal welfare and global food security

Filamentous fungi (moulds), yeast-like fungi, and oomycetes cause life-threatening infections of humans and animals and are a major constraint to global food security, constituting a significant economic burden to both agriculture and medicine. As well as causing localized or systemic infections, certain species are potent producers of allergens and toxins that exacerbate respiratory diseases or cause cancer and organ damage. We review the pathogenic and toxigenic organisms that are etiologic agents of both animal and plant diseases or that have recently emerged as serious pathogens of immunocompromised individuals. The use of hybridoma and phage display technologies and their success in generating monoclonal antibodies for the detection and control of fungal and oomycete pathogens are explored. Monoclonal antibodies hold enormous potential for the development of rapid and specific tests for the diagnosis of human mycoses, however, unlike plant pathology, their use in medical mycology remains to be fully exploited.

Detection of 'long-haired' Saprolegnia (S. parasitica) isolates using monoclonal antibodies

The ability of five monoclonal antibodies (Mabs) raised against a pathogenic Saprolegnia parasitica isolate from brown trout to detect and differentiate between isolates with bundles of long hairs (S. parasitica) and other Saprolegnia species was determined by means of an indirect immunofluorescence assay. Four of the Mabs used recognized some of the long-haired S. parasitica isolates but also cross-reacted with other Saprolegnia species without bundles of hairs and with Achlya sp. The other Mab (named 18A6) was able to differentiate between the asexual and most of the sexual isolates in the group of long-haired S. parasitica isolates, but did not recognize Achlya sp. or the Saprolegnia species without bundles of hairs, with the exception of S. hypogyna. These results indicate that isolates with bundles of long hairs are closely related with other members of genus Saprolegnia and share several antigens. However, Mab 18A6 seems to recognize an epitope that is expressed mainly in the asexual isolates in the long-haired S. parasitica isolates.

Antibody engineering--a valuable asset in preventing closed environment epidemics

Investigations of Mir, Space Shuttle, Skylab and Apollo missions report extensive colonisation of the spacecraft by bacteria and fungi, which can lead to degradative effects on spacecraft equipment and devastating effects on space-grown crops. More than 80% of terrestrial greenhouse epidemics are due to the fungal genera Phytophthora, Pythium and Fusarium, which have been found in life support system test-beds. The advent of recombinant antibody technologies, including ribosome display and phage display, has made it possible to develop antibodies against virtually any toxin or organism and allows for maturation of antibodies by in vitro molecular evolution. These antibodies may play an important role in an integrated pest management regime for life support systems. Efficacy of existing fungal countermeasures could be increased by chemical linkage to antibodies, which target the site of action of the biocide or trap the pathogen in a biofilter. Novel recombinant antibody-biocide fusions can be expressed in situ by plants or symbiotic microbes to create direct disease resistance.

Selection of Drug-Tolerant Strains of Pythium sylvaticum Using Sublethal Enrichment

ABSTRACT Sublethal enrichment was used to generate mutants of Pythium sylvaticum tolerant to kanamycin and tetracycline. Kanamycin tolerance was readily generated, and mutants had growth rates similar to wild-type isolates at antibiotic concentrations lethal to wild-type isolates. Based on crosses between wild-type and mutant isolates, two types of inheritance of tolerance were identified. A high level of kanamycin tolerance was inherited in progeny only when the maternal parent was drug tolerant and was correlated with the inheritance of maternal mitochondrial DNA. A lower level of tolerance was observed in some progeny when the paternal parent was tolerant to the antibiotic and, based on the lack of inheritance of paternal mitochondrial DNA, was presumably nuclear-encoded. Selection of mutants tolerant to tetracycline took longer to generate than kanamycin-tolerant mutants. Based on crosses between tolerant and wild-type parents, tolerance to tetracycline was nuclear-encoded. Tolerance to both antibiotics was stable, with cultures retaining tolerance following repeated transfers on nonamended medium and after storage for 7 years.

Characterization of a cell-surface antigen isolated from the plant pathogen Phytophthora parasitica var. nicotianae

The genus Phytophthora contains several species that are pathogenic to plants. Phytophthora parasitica var. nicotianae is the causal agent of the black shank disease of tobacco. From this fungus we have isolated and purified to homogeneity a 34-kDa glycoprotein (GP34) that elicits defence responses in tobacco. Among other features, this glycoprotein contains the rare amino acid hydroxyproline. Antibodies against GP34 permitted us to study its localization in vitro and in planta. Ultrastructural cytochemistry using immunogold labelling shows that GP34 is present in the cell wall into which it is secreted by vesicles when the fungus is grown on synthetic medium. In zoospores, labelling precedes and is strictly associated with the formation of a new cell wall. At early stages of infection of tobacco, only a faint labelling of the mycelium is observed. Later on it is enhanced in the incompatible interaction between the fungus and a resistant host cultivar. Key words: cell wall, elicitor, hydroxyproline, Phytophthora, tobacco.

Dynamics of fungal pathogens in host plant tissues

To develop efficient control measures against fungal plant pathogens, the dynamics of host plant colonization during disease development and the interactions among fungi within host plant tissues need to be clarified. These studies require accurate quantitative estimation of specific fungal biomass in plant tissues. This has been approached by direct-microscopic methods, cultural methods, chemical determinations of fungal components, serological methods, and molecular methods. Among these methods, serological and molecular methods provide rapid, specific, and sensitive quantitative measures of fungal biomass in host plant tissues. Therefore, studies on fungal dynamics of host plant colonization using these two methods are presented. Some examples of species interactions among pathogenic fungi within host plants, such as synergism and competition, are reviewed and the usefulness of serological and molecular methods for studies on these interactions is presented. These quantitative methods will provide helpful information for understanding the ecology of plant pathogenic fungi, such as the dynamics of host plant colonization and species interactions. Key words: quantitative methods, fungal biomass, ELISA, PCR, fungal colonization, species interaction.

Identification of glycoproteins specific to biotrophic intracellular hyphae formed in the Colletotrichum lindemuthianum-bean interaction

Monoclonal antibodies (MAbs) specific for intracellular for hyphae (IH, i.e. infection vesicles and primary hyphae). Appressoria/germ tubes and conidia of Colletotrichum lindemuthianum (Sace, & Magn.) Briosi & Cav. isolated from infected leaves of Phaseolus vulgoria L. were obtained using a co-immunization procedure. One of the MAhs; UB25, bound specifically to IH in immunofluorescence immunogold and Western blot assays: it showed no affinity for conidia, conidial germ tubes, appressoria or appressorial germ tubes growing in vitro, of for any plant components. Immunogold labeling of infected tissue prepared by high pressure freezing, freeze-substitution and low temperature embedding showed that the UB25 antigen was present in the interfacial matri surrounding IH and in the fungal wall. The antigen was confined to infection vesicles and primary hyphae in contact with host protoplast and could not be detected in primary hyphae growing in intercellular spaces. UB25 recognizes a protein epitope present in a set of N-linked glycoproteins. These glycoproteins are expressed at an early stage of intracellular development, suggesting a possible role in biotrophy or recognition.