The plant cell wall (CW) is a complex and dynamic structure mainly composed of polysaccharides and proteins affecting its mechanical properties, remodeling and disassembly. CW polysaccharides include a cellulose-hemicellulose network embedded in a cohesive pectin matrix . Pectins are synthesized in a highly methylesterified form in Golgi apparatus and demethylesterified in muro by pectin methylesterases (PMEs). PMEs play a central role in controlling CW integrity in plant growth and resistance to pathogens. In addition to the transcriptional control, PME activity is finely regulated by two classes of proteins: PME-specific subtilases (SBTs) and PME inhibitors (PMEIs). PMEs, PMEIs and SBTs belongs to large multigene families subdivided in subfamilies based on sequence similarity and including members possibly sharing common biological functions. Recent evidences indicate the role of pathogen-induced PMEs in plant immunity.
Botrytis cinerea, the causal agent of grey mold disease, is a broad-spectrum fungal necrotroph that causes serious pre and post-harvest rot in more than 200 species worldwide including important fruit crops. The aim of the project is to study the role of PME17 a PME isoform, strongly induced by B.cinerea in plant immunity. In particular we will focus on PME17 regulation by specific PMEIs and SBTs isoforms in response to B. cinerea to identify new candidate genes involved in resistance to pathogens.
Cross-disciplinary and innovative approaches of cell biology, biochemistry, glycomics and functional genomics will be exploited on genotypes of Arabidopsis thaliana altered in PME activity and resistance to B.cinerea. Our findings, will be extended to Vitis vinifera , an important crop species sensitive to B.cinerea, to aid the identification of cell wall biochemical markers useful for a future selection of cultivars improved in resistance to pathogens and in food quality.
Botrytis cinerea, the cause of grey mold disease, is considered the second most important fungal plant pathogen at global level. Grey mold disease is most destructive on mature tissues and fruits of hosts, therefore serious damage is caused following harvest of apparently healthy material and the subsequent transport to long distant markets . This filamentous fungus infects more than 200 plant species in a variety of organs including fruits, flowers, and leaves. Apart from tomato, the host range of B. cinerea includes other economically important crops such as grapes. Different grapevine cultivars are vulnerable to B. cinerea and the risk of infection is predicted to increase with global warming and higher precipitation levels. Control of fungal infections remains problematic. Application of fungicides is the most commonly used method to control fungal diseases, although it is expensive and not always effective and the risk of fungicide pollution limits their use. Moreover, fungicide resistance is an increasingly problematic issue, with significant proportions of the fungal population being resistant to fungicides.
The project will provide novel knowledge on biochemical traits and genetic sources to increase the long-term plant resistance to fungal pathogens.
The new cell wall-based approach to plant disease control in fact, makes possible to avoid the appearance of resistance phenomena in the pathogen populations, without negative effect in the ecosystem.
In addition, the new pectin methylesterification traits and their underlying genes identified in the project will represent an excellent source to generate crop varieties with a durable resistance to B. cinerea, either by traditional breeding or by genetic engineering. The new traits identified could also represent molecular markers potentially useful for the selection of crop cultivars resistant to B.cinerea.
The results foreseen in this proposal will have an impact well beyond the species and pathogen here studied: most likely, analogous molecular mechanisms control PME activity during infection with other necrotrophic pathogens and in other crop species.
The availability of new resistant genotypes can reduce the need of fungicides and minimize their impact on the environment, ensuring a high standard of plant yield and food quality resulting in a long-term benefit for citizens, economy and society.
Finally efforts that will be made to provide new experimental tools to analyze, at molecular level, the plant defense mechanisms and fruit quality (i.e. pectin related biochemical traits and genetic determinants ) and new pathogen resistant commercial food crops varieties will be available to the scientific community and consumers.