Mw.drs. N.E.M. (Nikkie) van Bers: “Hypervariability in pathogenesis”

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17 Jun 2008 11:00
Unit: Wageningen University
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

 Plant parasitic nematodes secrete a cocktail of effector molecules, which are involved in several aspects of the interaction with the host, eg. in host defense suppression, in migration and in feeding cell formation. In this thesis, we performed the first study on 10 novel peptide genes, believed to be important for parasitism of the potato cyst nematode, Globodera rostochiensis.

Nine of the peptides described here belong to the SECPEP gene family, and we show that diversifying selection is a likely driver of the molecular evolution of the SECPEPs. This selection pressure resulted in hypervariable genes, with a highly dissimilar region coding for the mature peptide, while the region coding for the signal peptide for secretion is conserved between the family members. Despite this hypervariability in sequence, the SECPEPs all share a small size (3-12 kDa), a positive charge and a C-x-G γ-core motif. These characteristics are also found in several classes of antimicrobial peptides, and in the NEMPEP peptide secreted by G. rostochiensis.

Currently, there are two models regarding the functional role of the SECPEPs and NEMPEP. The first one concerns a role as an antimicrobial peptide, which could protect the host plant against secondary infections by opportunistic microbes.  As a competing hypothesis, the high hydrophilicity of the peptides may point to a role as peptide hormone. As such, they may be involved in redirecting cell cycle or hormonal regulation upon feeding cell formation.

Title thesis: "Characterization of genes coding for small hypervariable peptides in Globodera rostochiensis"
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