Dhr.ir. E.J. (Erik) Slootweg: ‘Structure, function and subcellular localization of the potato Resistance protein Rx1”

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23 okt 2009 13:30
Onderdeel: Wageningen University
Locatie: Aula, gebouw 362, Gen. Foulkesweg 1, Wageningen
Organisatie: Wageningen University
Promotor: prof.dr.ir. J. Bakker (Nematologie ihb fysiologie en moleculaire ecologie van nematoden)
Co-Promotor: Dr.ir. A. Goverse, Dr.ir. A. Schots

 Resistance proteins are a crucial part of the plant’s immune system, they specifically recognize pathogens and subsequently initiate the appropriate defence responses. Rx1 and Gpa2 are highly similar potato resistance proteins conferring resistance to Potato Virus  X and the plant parasitic nematode Globodera pallida respectively. Even though the functional mechanisms of the NB-LRR class of Resistance proteins, where Rx1 and Gpa2 belong to, have been studied for abbout fifteen years, many questions remain unanswered. In this thesis Resistance protein functioning is studied via several different approaches. By applying T7 cDNA phage display it was found that the N-terminal half of Rx1 has the tendency to bind highly basic peptides. The T7 phage display system itself was modified by applying a translation frameshift to enable the formation of phage particles carrying both a protein of interest and several copies of the yellow fluorescent protein, making them detectable by microscopic techniques. Exchanging sequences between Gpa2 and Rx1 identified the regions in the C-terminal LRR domain that are responsible for specific pathogen recognition, but also helped in identifying functional connections between the various subdomains that essential in the proteins functioning. This information, combined with structural models of the NB-ARC and LRR domain, was used to create a 3D structural model of the interaction between these domains. By fluorescently labelling Rx1 and its subdomains it was found that this protein is present in both the cytoplasm and the nucleus in the cell. When the elicitor of Rx1, the PVX coat protein, is targeted to the nucleus it no longer activates Rx1, showing that at least the recognition of PVX by Rx1 takes place in the cytoplasm.
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