Recente ontwikkelingen in detectie en identificatie van plantenpathogenen: van microscopie naar moleculaire diagnostiek

Het opsporen en identificeren van schadelijke organismen in planten, grond, teeltsubstraat, water of lucht vormt de basis van een veilige en duurzame gewasbescherming. Daarom bestaat er een grote behoefte aan diagnostische testen, die niet alleen de plantenpathogenen snel moeten kunnen detecteren en identificeren, maar liefst ook de concentratie van de ziekteverwekker moeten kunnen inschatten. Op deze manier kan een accuraat advies gegeven worden, zodat er, naargelang de aard en de ernst van de besmetting, op een verantwoorde manier (bij)gestuurd kan worde

Assessment of RNAi-induced silencing in banana (Musa spp.)

In plants, RNA- based gene silencing mediated by small RNAs functions at the transcriptional or post-transcriptional level to negatively regulate target genes, repetitive sequences, viral RNAs and/or transposon elements. Post-transcriptional gene silencing (PTGS) or the RNA interference (RNAi) approach has been achieved in a wide range of plant species for inhibiting the expression of target genes by generating double-stranded RNA (dsRNA). However, to our knowledge, successful RNAi-application to knock-down endogenous genes has not been reported in the important staple food crop banana

Mode of action of plant defensins suggests therapeutic potential

Higher vertebrates can rely both on an innate as well as an adaptive immune system for defense against invading pathogens. In contrast, plants can only employ an innate immune system that largely depends on the production of antimicrobial compounds such as plant defensins and other pathogenesis-related proteins. Plant defensins are ubiquitous, cationic, cysteine-rich plant peptides and have a folding pattern that shares high similarity to defense peptides of mammals and insects, suggesting an ancient and conserved origin. A large number of plant defensins appear to display antifungal activity. Some of these defensins have been found to interact with fungal-specific components in the plasmamembrane, resulting in membrane permeabilization. This makes them an attractive source of potential therapeutics to treat fungal infections

Mode of action of plant defensins suggests therapeutic potential

Higher vertebrates can rely both on an innate as well as an adaptive immune system for defense against invading pathogens. In contrast, plants can only employ an innate immune system that largely depends on the production of antimicrobial compounds such as plant defensins and other pathogenesis-related proteins. Plant defensins are ubiquitous, cationic, cysteine-rich plant peptides and have a folding pattern that shares high similarity to defense peptides of mammals and insects, suggesting an ancient and conserved origin. A large number of plant defensins appear to display antifungal activity. Some of these defensins have been found to interact with fungal-specific components in the plasmamembrane, resulting in membrane permeabilization. This makes them an attractive source of potential therapeutics to treat fungal infections

Detecting single nucleotide polymorphisms using DNA arrays for plant pathogen diagnosis

The lack of a rapid and reliable means for routine pathogen identification has been one of the main limitations in plant disease management, and has pushed the development of culture-independent, molecular approaches. Currently, DNA array technology is the most suitable technique for high-throughput detection and identification, as well as quantification, of multiple pathogens in a single assay. Closely related pathogens that may have completely different host ranges or pathogenicity often differ in only a single to a few base pairs in genes that may be targeted for identification. Therefore, the ability to discriminate single nucleotide polymorphisms (SNPs) should be pursued in any diagnostic assay. In this paper, we demonstrate the utility of DNA array technology to detect SNPs while accounting for specific criteria such as the position of the mismatch, the sequence of the oligonucleotide, and the length and amount of labeled amplicons that are hybridized. When disregarding mismatches at the extreme ends of the oligonucleotides, cross hybridization to single mismatch oligonucleotides is rare when processing environmental samples that contain genetic material from unknown sources. In addition to plant pathology, this study is relevant for any field of research where DNA arrays are used to detect mutations or polymorphisms, ranging from human diagnostics to environmental microbiology and microbial ecology

Therapeutic potential of antifungal plant and insect defensins

To defend themselves against invading fungal pathogens, plants and insects largely depend on the production of a wide array of antifungal molecules, including antimicrobial peptides such as defensins. Interestingly, plant and insect defensins display antimicrobial activity not only against plant and insect pathogens but also against human fungal pathogens, including Candida spp. and Aspergillus spp. This review focuses on these defensins as novel leads for antifungal therapeutics. Their mode of action, involving interaction with fungus-specific sphingolipids, and heterologous expression, required for cost-effective production, are major assets for development of plant and insect defensins as antifungal leads. Studies evaluating their in vivo antifungal efficacy demonstrate their therapeutic potential

Improvement of Bananas for Black Sigatoka and panama Disease Resistance through Genetic Manipulation

Bananas are a staple food in Eastern Africa, with 25.3% of the total world production. The production is, however, threatened by the presence of several diseases, of which the fungal diseases black sigatoka and Panama disease are the most important. With the development of embryogenic cell suspension cultures, the isolation of protoplasts therefrom and their successful regeneration, an invaluable vegetative material for genetic manipulation of bananas became available. The discovery of new types of antifungal proteins (AFP\u2019s) and the cloning of their encoding genes provide a source of resistance to fungal diseases that can be introduced into plant cells by genetic engineering. Transformation techniques are currently under investigation. Electroporation of banana protoplasts have resulted in transient expression frequencies of more than 1% as visualized by the action of the \u3b2-glucuronidase (GUS) marker gene. Experiments with particle bombardment on cell suspensions have resulted in transient expression frequencies up to 3300 blue spots/0.5 ml cells, and stable transformants have also been selected. Optimisation of the cell suspension culture technique and transformation methodology is in progress