The discovery of type III secretion systems during the last decade has dramatically changed our understanding of the molecular basis of bacterial pathogenicity. Type III secretion systems are conserved in animal and plant bacterial pathogens and are involved in the delivery of bacterial effector proteins into the host cells. In plants, the identification of bacterial effectors is of an outstanding importance, since the understanding of the molecular processes leading to disease development and the identification of the corresponding molecular targets in the eukaryotic cell opens the way to new biotechnological strategies for crop protection.
In the plant pathogen R. solanacearum biochemical and genetic approaches led to the identification of several proteins that are exported through the Type III apparatus. The advent of the genome sequencing projects has facilitated the identification of new effectors based on the similarity or the structural features of predicted proteins, as well as the coregulation with th e Type III secretion system. A group of related genes that are called the awr family and have no similarities in the databases has been identified through analysis of R. solanacearum genome sequence. Mutation of one awr gene dramatically decreases R. solana cearum aggressivity on tomato, which renders the AWR proteins excellent candidates as effector proteins that carry out a function within the plant cell.
The aim of this project is to characterise thoroughly this gene family in search for type III-dependent effectors with a major role in pathogenicity. The process will include:
1) demonstration of protein translocation into plant cells,
2) study of their expression profile and analysis of the mutant phenotype regarding pathogenicity,
3) subcellular localisati on of the AWR effector proteins once inside the plant and
4) identification of the plant targets
5) establishment of the role of AWR effectors and their interactors in pathogenicity or defence.
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