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A ubiquitin carboxyl extension protein secreted from a plant‐parasitic nematode Globodera rostochiensis is cleaved in planta to promote plant parasitism
Author(s) -
Chronis Demosthenis,
Chen Shiyan,
Lu Shunwen,
Hewezi Tarek,
Carpenter Sara C.D.,
Loria Rosemary,
Baum Thomas J.,
Wang Xiaohong
Publication year - 2013
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12125
Subject(s) - biology , globodera rostochiensis , effector , heterodera avenae , nematode , potato cyst nematode , signal peptide , secretion , ubiquitin , rna interference , gene expression , microbiology and biotechnology , gene , biochemistry , peptide sequence , rna , ecology
Summary Nematode effector proteins originating from esophageal gland cells play central roles in suppressing plant defenses and in formation of the plant feeding cells that are required for growth and development of cyst nematodes. A gene ( G r UBCEP 12 ) encoding a unique ubiquitin carboxyl extension protein ( UBCEP ) that consists of a signal peptide for secretion, a mono‐ubiquitin domain, and a 12 amino acid carboxyl extension protein (CEP12) domain was cloned from the potato cyst nematode G lobodera rostochiensis . This G r UBCEP 12 gene was expressed exclusively within the nematode's dorsal esophageal gland cell, and was up‐regulated in the parasitic second‐stage juvenile, correlating with the time when feeding cell formation is initiated. We showed that specific G r UBCEP 12 knockdown via RNA interference reduced nematode parasitic success, and that over‐expression of the secreted Gr Δ SP UBCEP 12 protein in potato resulted in increased nematode susceptibility, providing direct evidence that this secreted effector is involved in plant parasitism. Using transient expression assays in N icotiana benthamiana , we found that G r Δ SP UBCEP 12 is processed into free ubiquitin and a CEP 12 peptide ( G r CEP 12) in planta , and that G r CEP 12 suppresses resistance gene‐mediated cell death. A target search showed that expression of RPN 2a , a gene encoding a subunit of the 26S proteasome, was dramatically suppressed in G r ΔSP UBCEP 12 but not G r CEP 12 over‐expression plants when compared with control plants. Together, these results suggest that, when delivered into host plant cells, G r Δ SP UBCEP 12 becomes two functional units, one acting to suppress plant immunity and the other potentially affecting the host 26S proteasome, to promote feeding cell formation.