SPRYSECs: activators and suppressors of effector-triggered immunity in plants
Le résumé fourni par la source
The potato cyst nematodes Globodera rostochiensis and G. pallida invade roots of Solaneceous host plants where they transform cells near the vascular cylinder into a permanent feeding site. The host cell modifications are most likely brought about by a complex mixture of proteins in the stylet secretions of the nematodes. Plants use highly specific NB-LRR immune receptors to recognize effectors in these stylet secretions. Effector-triggered immunity to parasitic nematodes often involves a programmed cell death in and around the feeding site. The SPRYSEC effector RBP-1 from G. pallida is recognized by the CC-NB-LRR immune receptor Gpa2 from potato and evasion of recognition depends on a single amino acid substitution. Whether the activation of Gpa2 depends on a direct or indirect interaction remains elusive. Remarkably, the effector SPRYSEC-19 of G. rostochiensis physically associates in planta with the leucine-rich repeat (LRR) domain of a member of the SW5 resistance gene cluster in tomato (Solanum lycopersicum). Unexpectedly, this interaction did not trigger defense-related programmed cell death and resistance to G. rostochiensis. By contrast, agroinflitration assays showed that the co-expression of SPRYSEC19 in leaves of Nicotiana benthamiana suppresses effector- triggered programmed cell death mediated by several, but not all, CC-NB-LRR immune receptors. Furthermore, SPRYSEC-19 abrogated the PVX resistance mediated by the CC-NB-LRR resistance protein Rx1 of tomato, and resistance to Verticillium dahliae mediated by an unidentified resistance gene in potato. Altogether, our data demonstrates that effectors of the SPRYSEC family in potato cyst nematodes are both activators and suppressors of plant immunity. Currently, we are studying functional and evolutionary aspects involved in effector-triggered immunity and suppression by SPRYSECs to get a better understanding in nematode virulence and host resistance.
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