PhD defence Wiebe Postma

Title Thesis: On the modulation of innate immunity by plant-parasitic cyst nematodes

Promotor J (Jaap) Bakker
Copromotor G (Geert) Smant A (Aska) Goverse
Organisatie Laboratory of Nematology, Wageningen University

do 13 juni 2013 11:00 tot 12:30

Locatie Auditorium, building number 362
Generaal Foulkesweg 1
6703 BG Wageningen


Plant-parasitic cyst nematodes are major agricultural pests worldwide. These obligate endoparasites invade the roots of host plants where they transform cells near the vascular cylinder into a permanent feeding site. Plants possess a multilayered innate immune system consisting of different types of extracellular and intracellular immune receptors. These enable detection of most invading nematodes and initiate immune responses that result in resistance. Many plant pathogens use effectors to overcome resistance. Here, modulation of plant innate immunity by plant-parasitic cyst nematodes was investigated. Extracellular immune receptor signaling and hormone-mediated signaling pathways were found to contain the infection of susceptible Arabidopsis thaliana with Heterodera schachtii. A large family of effectors was identified in Globodera rostochiensis. One of these so-called SPRYSECs interacted with a novel CC-NB-LRR type resistance protein of a susceptible tomato without inducing resistance responses. Instead, the effector was found to suppress defense-related programmed cell death and resistance mediated by several CC-NB-LRR type resistance proteins. In addition, a secreted antimicrobial peptide was identified in G. rostochiensis. Plant-parasitic cyst nematodes most likely secrete effectors that protect against plant immune responses and secondary infections. The current evidence for the existence of immune modulating effectors is reviewed and directions for further research are given.