Analysis of Putative Apoplastic Effectors from the Nematode, Globodera rostochiensis, and Identification of an Expansin-Like Protein That Can Induce and Suppress Host Defenses

Abstract

The potato cyst nematode, Globodera rostochiensis, is an important pest of potato. Like other pathogens, plant parasitic nematodes are presumed to employ effector proteins, secreted into the apoplast as well as the host cytoplasm, to alter plant cellular functions and successfully infect their hosts. We have generated a library of ORFs encoding putative G. rostochiensis putative apoplastic effectors in vectors for expression in planta. These clones were assessed for morphological and developmental effects on plants as well as their ability to induce or suppress plant defenses. Several CLAVATA3/ESR-like proteins induced developmental phenotypes, whereas predicted cell wall-modifying proteins induced necrosis and chlorosis, consistent with roles in cell fate alteration and tissue invasion, respectively. When directed to the apoplast with a signal peptide, two effectors, an ubiquitin extension protein (GrUBCEP12) and an expansin-like protein (GrEXPB2), suppressed defense responses including NB-LRR signaling induced in the cytoplasm. GrEXPB2 also elicited defense response in species- and sequence-specific manner. Our results are consistent with the scenario whereby potato cyst nematodes secrete effectors that modulate host cell fate and metabolism as well as modifying host cell walls. Furthermore, we show a novel role for an apoplastic expansin-like protein in suppressing intra-cellular defense responses.

The Meloidogyne graminicola effector Mg16820 is secreted in the apoplast and cytoplasm to suppress plant host defense responses

“…However, in contrast with Mg16820, the different activities of Msp40 appeared in the same cell compartment, the nucleus and cytoplasm, whereas Mg16820 works in the apoplast as well as in the cytoplasm. The Globodera rostochiensis effector GrUBCEP12, with and without SP, was able to suppress several elicitor‐induced cell death pathways (Ali et al, ). Although it was not confirmed by subcellular localization that the effector GrUBCEP12 was indeed transported to the apoplast, it was confirmed that this effector works on several HR pathways.…”

Functional and Genetic Analysis Identify a Role for Arabidopsis ARGONAUTE5 in Antiviral RNA Silencing

“…To generate the 35S:R-LUC-expressing construct, the pGreenII61 MCS (including the 35S expression cassette) was first subcloned into the AscI and StuI sites of pEAQ-SelectK (Sainsbury et al, 2009) to produce the pEAQ-SE expression vector (Ali et al, 2015). Subsequently, Renilla luciferase was excised from pRL-SV40 (Promega) with NheI and XbaI and cloned into the XbaI site of pEAQ-SE.…”

A Plasmodium‐like virulence effector of the soybean cyst nematode suppresses plant innate immunity

“…Multiple effectors from plant‐parasitic nematodes have been shown to suppress basal and/or hypersensitive cell death response (HR)‐related immune responses, and their mechanisms include scavenging reactive oxygen species (Chen et al ., ; Lin et al ., ), nonphotochemical quenching (Lozano‐Torres et al ., ) and less well‐understood mechanisms (Chronis et al ., ; Ali et al ., ,b; Chen et al ., ). Some of these effectors can even activate immune responses (Lozano‐Torres et al ., ; Ali et al ., ,b). In heterologous assays, we found that HgGLAND18 ‐ sp strongly suppresses both canonical basal and HR immune responses.…”