Title: The novel GrCEP12 peptide from the plant-parasitic nematode Globodera rostochiensis suppresses flg22-mediated PTI Authors
Submitted to: Plant Signaling and Behavior
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 10, 2013
Publication Date: June 26, 2013
Citation: Chen, S., Chronis, D.N., Wang, X. 2013. The novel GrCEP12 peptide from the plant-parasitic nematode Globodera rostochiensis suppresses flg22-mediated PTI. Plant Signaling and Behavior. 8(9):e25359. Interpretive Summary: The potato cyst nematode Globodera rostochiensis (a.k.a. golden nematode) is a root pathogen that secretes effector proteins into plant cells to enable successful infection. We have recently shown that the effector ubiquitin carboxyl extension protein (GrUBCEP12) secreted from G. rostochiensis is required for nematode parasitism. GrUBCEP12 was found to be processed into free ubiquitin and a novel small peptide (GrCEP12) in planta. Interestingly transgenic potato plants overexpressing the derived GrCEP12 peptide were more susceptible to nematode infection, indicating a role of GrCEP12 in host defense suppression. To evaluate this hypothesis, we investigated whether GrCEP12 can suppress plant basal defense (also known as PTI) responses triggered by flg22, a derivative peptide of bacterial flagellin that is commonly used in PTI assays. Our results clearly demonstrated an activity of GrCEP12 in PTI suppression. This study provides new evidence for a role of nematode secreted effectors in host defense suppression and adds new knowledge of the molecular basis of G. rostochiensis parasitism.
Technical Abstract: The potato cyst nematode Globodera rostochiensis is a biotrophic pathogen that secretes effector proteins into host root cells to promote successful plant parasitism. In addition to the role in generating within root tissue the feeding cells essential for nematode development, nematode secreted effectors are becoming recognized as suppressors of plant immunity. Recently we reported that the effector ubiquitin carboxyl extension protein (GrUBCEP12) from G. rostochiensis is processed into free ubiquitin and a 12-amino acid GrCEP12 peptide in planta. Transgenic potato lines overexpressing the derived GrCEP12 peptide showed increased susceptibility to G. rostochiensis and to an unrelated bacterial pathogen of Streptomyces scabies, suggesting that GrCEP12 has a role in suppressing PAMP-triggered immunity (PTI) during the parasitic interaction. To further confirm that GrCEP12 is a suppressor of PTI, we evaluated whether GrCEP12 suppress flg22-induced PTI responses in Nicotiana benthamiana. Interestingly we found that transient expression of GrCEP12 in N. benthamiana leaves suppressed ROS production, the induction of a couple of PTI marker genes, and callose deposition triggered by the bacterial PAMP flg22, providing direct evidence that GrCEP12 indeed has an activity in PTI suppression.