The expression of antifungal peptides in grapevine cultivars
Vivier, M A
University of Stellenbosch. Faculty of AgriSciences. Institute for Wine Biotechnology
De Beer, A
The Institute for Wine Biotechnology (IWBT) chose the subject of manipulated disease resistance as main theme for the grapevine improvement programme. In this broad subject we are currently focusing on resistance to fungal infections as well as resistance to viral infections (in collaboration with Dr J T Burger, University of Stellenbosch. Department of Genetics). Several approaches have been implemented to potentially enhance disease resistance against the major fungal pathogens that cause grey mould, downy mildew and powdery mildew. One of these approaches involves the use of polygalacturonase-inhibiting proteins (PGIPs) (Winetech funded project, IWBT 4/3). In this application, as well as another project (see project IWBT4/6), different approaches are suggested to obtain the same goal, namely that of enhanced fungal resistance in grapevine.
Botrytis cinerea is the causal agent of grey mould of grapevine and is generally regarded as the most important economical fungal pathogen of grapevine. This pathogen may cause extreme damage if weather conditions are optimal for the infection process. Regardless of various approaches of control or prevention of the disease, there is currently no successful alternative to the chemical spraying of vineyards. The use of chemical fungicides presents only temporary and cosmetic solutions and in addition proves to be expensive as well as unpopular with an increasing group of consumers whom are protesting against the excessive use of agricultural chemicals.
The alternative is to ‘improve’ the grapevine by means of genetic manipulations to enhance the plant?s resistance to the pathogen. One of the possible strategies exploits a system that is already present in a variety of plants, namely the use of antifungal peptides to control pathogen attack. Antifungal peptides have been isolated from various plant and weed species (as well as other resources) and have proven to be an effective control mechanism against various pathogens.
The aim of this project comprises the integration of an antifungal peptide with activity against Botrytis cinerea in the grapevine genome, in an attempt to equip plants with an inherent resistance against Botrytis attacks. The strategy that will be followed is to target the peptide to the apoplastic environment of plant cells (where the initial contact with most pathogens take place) by means of a signal peptide that is under the control of a strong plant promoter and terminator. Furthermore, a study will be undertaken to determine whether the peptide can be stabilised in the plant and protected against protease activity by making fusion proteins. Therefore, the study can possibly lead to transgenic plants with increased Botrytis resistance as well as a better understanding of the process of expression of small peptides on plant cell surfaces or as fusion proteins. In addition, expression of antifungal peptides in grapevine as a possible means of disease resistance is a novel approach.
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