Abstract

SummarySedentary plant‐parasitic nematodes (PPNs) induce and maintain an intimate relationship with their host, stimulating cells adjacent to root vascular tissue to re‐differentiate into unique and metabolically active ‘feeding sites’. The interaction between PPNs and their host is mediated by nematode effectors. We describe the discovery of a large and diverse family of effector genes, encoding C‐TERMINALLY ENCODED PEPTIDE (CEP) plant hormone mimics (RrCEPs), in the syncytia‐forming plant parasite Rotylenchulus reniformis. The particular attributes of RrCEPs distinguish them from all other CEPs, regardless of origin. Together with the distant phylogenetic relationship of R. reniformis to the only other CEP‐encoding nematode genus identified to date (Meloidogyne), this suggests that CEPs probably evolved de novo in R. reniformis. We have characterized the first member of this large gene family (RrCEP1), demonstrating its significant up‐regulation during the plant–nematode interaction and expression in the effector‐producing pharyngeal gland cell. All internal CEP domains of multi‐domain RrCEPs are followed by di‐basic residues, suggesting a mechanism for cleavage. A synthetic peptide corresponding to RrCEP1 domain 1 is biologically active and capable of up‐regulating plant nitrate transporter (AtNRT2.1) expression, whilst simultaneously reducing primary root elongation. When a non‐CEP‐containing, syncytia‐forming PPN species (Heterodera schachtii) infects Arabidopsis in a CEP‐rich environment, a smaller feeding site is produced. We hypothesize that CEPs of R. reniformis represent a two‐fold adaptation to sustained biotrophy in this species: (i) increasing host nitrate uptake, whilst (ii) limiting the size of the syncytial feeding site produced.

Highlights

  • Sedentary plant-parasitic nematodes (PPNs) induce and maintain an intimate relationship with their host

  • The multinucleate feeding sites of the most widely studied sedentary PPNs can be divided into two general classes: (i) the cluster of individual giant cells of the root-knot nematodes, each formed from a single cell by multiple rounds of mitosis in the absence of cytokinesis; (ii) the syncytial feeding sites of the cyst, reniform and false-root-knot nematodes, formed by partial cell wall dissolution and subsequent protoplast fusion of multiple adjacent cells (Grymaszewska and Golinowski, 1998; Holtmann et al, 2000; Jones and Payne, 1977; Rahman Razak and Evans, 1976; Robinson et al, 1998; Sobczak and Golinowski, 2011)

  • Using a primer pair targeting a single C-TERMINALLY ENCODED PEPTIDE (CEP)-like gene, multiple polymerase chain reaction (PCR) products were generated from genomic DNA; these were cloned and sequenced

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Summary

SUMMARY

Sedentary plant-parasitic nematodes (PPNs) induce and maintain an intimate relationship with their host, stimulating cells adjacent to root vascular tissue to re-differentiate into unique and metabolically active ‘feeding sites’. We describe the discovery of a large and diverse family of effector genes, encoding C-TERMINALLY ENCODED PEPTIDE (CEP) plant hormone mimics (RrCEPs), in the syncytia-forming plant parasite Rotylenchulus reniformis. We have characterized the first member of this large gene family (RrCEP1), demonstrating its significant upregulation during the plant–nematode interaction and expression in the effector-producing pharyngeal gland cell. When a non-CEP-containing, syncytia-forming PPN species (Heterodera schachtii) infects Arabidopsis in a CEP-rich environment, a smaller feeding site is produced. We hypothesize that CEPs of R. reniformis represent a two-fold adaptation to sustained biotrophy in this species: (i) increasing host nitrate uptake, whilst (ii) limiting the size of the syncytial feeding site produced

INTRODUCTION
RESULTS AND DISCUSSION
EXPERIMENTAL PROCEDURES
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