Ms. K.B. (Kamila) Koropacka: Molecular contest between potato and the potato cyst nematode Globodera pallida: modulation of Gpa2-mediated resistance

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5 Feb 2010 16:00
Unit: Laboratory of Nematology
Location: Aula, building 362, Gen. Foulkesweg 1, Wageningen
Organisation: Wageningen University
Promotor: prof.dr.ir. J. Bakker (Nematology)
Co Promotor: Dr.ir. G. Smant/ Dr.ir. A. Goverse

 The potato cyst nematode Globodera pallida is an important pest of cultivated potato. The best way to control these pathogen is the exploitation and use of host resistance. This includes the potato gene Gpa2 (Van der Vossen et al., 2000) which is highly homologous to Rx1 that confers resistance against potato virus X (Bendahmane et al., 1999). Both genes encode a protein with a nucleotide-binding leucine-rich repeat (NBS-LRR) domain and a short coiled-coil (CC) domain at the N-terminus. We have shown that a LRR domain is a major determinant of Rx1 or Gpa2 specificity, whereas the CC-NBS domains can be exchanged. Using chimeric constructs allowed to narrow down the region required for nematodes recognition to residues between 808 and 912 nucleotides in Gpa2. Further, the 3D structure of the LRR domain was predicted where 7 of the Gpa2 specific amino acids map to the concave surface of the horseshoe-like structure of the LRR domain.

Recently a RBP protein secreted by juveniles of G. pallida, which shows strong homology to the SPRY domain of the Ran-binding protein RanBPM, was identified as a Gpa2 elicitor (Sacco et al., 2009). In this studies, 10 very close homologous of RBP-1 were found and tested for their ability to elicit the Gpa2 dependent response. Those homologues possess a different potential in activating Gpa2 what was correlated with a single amino-acid substitution. Non-eliciting (RBPROOK2, RBPROOK4) variants have a serine instead of proline at position 166 (S166P) within the SPRY domain. This mutation modifies the shape of the loop extended from the protein core what affects the potential surface for protein-protein interactions. Additionally, it was shown that the non-eliciting variants (RBPROOK2, RBPROOK4)  can suppress the activation of Gpa2 in response to the eliciting RBPs.
Thesis: Mw. K.B. (Kamila) Koropacka: Molecular contest between potato and the potato cyst nematode Globodera pallida: modulation of Gpa2-mediated resistance
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