Molecular dynamics of the RBP-1 effector gene family in the potato cyst nematode Globodera pallida

The potato cyst nematode species Globodera rostochiensis and G. pallida have a narrow host range which is restricted to Solanaceous species, including tomato, potato and egg plant. Upon invasion of the roots, they transform cells near the vascular cylinder into a permanent feeding site on which they fully depend for their development. The host cell modifications are most likely induced by a complex mixture of proteins which are secreted by the nematode during early stages of infection. However, host plants have evolved strategies to counterbalance the establishment of such a feeding relationship, including effector triggered immunity. In return, virulent plant parasitic nematodes have developed means to overcome host resistance. Recently, we demonstrated that members of the SPRYSEC family from the potato cyst nematode G. rostochiensis are able to suppress CC-NB-LRR mediated cell death and disease resistance in plants. Globodera pallida RBP-1 encodes a related secretory protein with a SPRY domain, which is specifically recognized by the potato immune receptor Gpa2. All RBP-1 variants found in the avirulent population of G.pallida (D383) elicit a Gpa2-dependent HR, while a virulent population (Rookmaker) possessed two variants which evade Gpa2 recognition due to a single DNA polymorphism. This is the result of diverifying selection, which has contributed to the expansion of this effector gene family in potato cyst nematodes. Here, we present novel data on the complexity and sequence diversity of the RBP-1 gene family, illustrating the molecular dynamics underlying the co-evolution between G. pallida and Solanaceous plant species. This will contribute to our understanding of nematode (a)virulence and the development of broadspectrum nematode resistance.