Abstract
The plant-parasitic nematode Heterodera schachtii is an obligate biotroph that induces syncytial feeding sites in roots of its hosts. Nematodes produce effectors that are secreted into the host and facilitate infection process. Here we identified H. schachtii protein disulphide isomerase (HsPDI) as a putative effector that interferes with the host’s redox status. In situ hybridization showed that HsPdi is specifically localized within esophageal glands of pre-parasitic second stage juveniles (J2). HsPdi is up-regulated in the early parasitic J2s. Silencing of HsPdi by RNA interference in the J2s hampers their development and leads to structural malfunctions in associated feeding sites induced in Arabidopsis roots. Expression of HsPDI in Arabidopsis increases plant’s susceptibility towards H. schachtii. HsPdi expression is up-regulated in the presence of exogenous H2O2, whereas HsPdi silencing results in increased mortality under H2O2 stress. Stable expression of HsPDI in Arabidopsis plants decreases ROS burst induced by flg22. Transiently expressed HsPDI in N. benthamiana leaves is localized in the apoplast. HsPDI plays an important role in the interaction between nematode and plant, probably through inducing local changes in the redox status of infected host tissue. It also contributes to protect the nematode from exogenous H2O2 stress.
Highlights
Plant-parasitic cyst nematodes are obligate biotrophs that induce and maintain intimate and long-term feeding relationships with their host plants
Our analysis showed no significant difference in number of infecting nematodes found on plants infected with J2s treated with Double stranded RNA (dsRNA) targeting HsPdi compared to those treated with dsRNA targeting GFP (Fig. 2A)
By analysing the juveniles that were exposed to H2O2 (5 or 10 mM) for 30 min, we found a significant increase in transcript abundance of the HsPdi when compared with water-treated control J2s (Fig. 6B)
Summary
Plant-parasitic cyst nematodes are obligate biotrophs that induce and maintain intimate and long-term feeding relationships with their host plants. It has recently been shown that infection of Arabidopsis by H. schachtii activates the plasma membrane-localised NADPH oxidase (RbohD and RbohF) to produce ROS, which, is required for proper infection and syncytium development[25]. These observations on parasitic nematodes together with other previously published literature led to the suggestion that redox homeostasis is crucial for both effective plant defence and successful parasitism[25,26]. The potato cyst nematode (Globodera rostochiensis) produces peroxiredoxins (PXN) and glutathione peroxidases (GXP), which are likely responsible for regulation of ROS level at nematode infection sites[27,37]
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