Abstract
BackgroundThe potato cyst nematode Globodera pallida has biotrophic interactions with its host. The nematode induces a feeding structure – the syncytium – which it keeps alive for the duration of the life cycle and on which it depends for all nutrients required to develop to the adult stage. Interactions of G. pallida with the host are mediated by effectors, which are produced in two sets of gland cells. These effectors suppress host defences, facilitate migration and induce the formation of the syncytium.ResultsThe recent completion of the G. pallida genome sequence has allowed us to identify the effector complement from this species. We identify 128 orthologues of effectors from other nematodes as well as 117 novel effector candidates. We have used in situ hybridisation to confirm gland cell expression of a subset of these effectors, demonstrating the validity of our effector identification approach. We have examined the expression profiles of all effector candidates using RNAseq; this analysis shows that the majority of effectors fall into one of three clusters of sequences showing conserved expression characteristics (invasive stage nematode only, parasitic stage only or invasive stage and adult male only). We demonstrate that further diversity in the effector pool is generated by alternative splicing. In addition, we show that effectors target a diverse range of structures in plant cells, including the peroxisome. This is the first identification of effectors from any plant pathogen that target this structure.ConclusionThis is the first genome scale search for effectors, combined to a life-cycle expression analysis, for any plant-parasitic nematode. We show that, like other phylogenetically unrelated plant pathogens, plant parasitic nematodes deploy hundreds of effectors in order to parasitise plants, with different effectors required for different phases of the infection process.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-923) contains supplementary material, which is available to authorized users.
Highlights
The potato cyst nematode Globodera pallida has biotrophic interactions with its host
We recently reported the full genome sequence of G. pallida [27] including a fully replicated life cycle transcriptome analysis and a preliminary description of the effectors likely to be present in this species
Subsequent studies have led to the identification of numerous other horizontally acquired cell wall modifying proteins in a wide range of Plant-parasitic nematodes (PPN), including cellulases, pectate lyases, xylanases, polygalacturonases, arabinogalactan galactosidases, arabinanases, carbohydrate binding modules (CBM) and expansin-like proteins
Summary
The potato cyst nematode Globodera pallida has biotrophic interactions with its host. Interactions of G. pallida with the host are mediated by effectors, which are produced in two sets of gland cells These effectors suppress host defences, facilitate migration and induce the formation of the syncytium. Globodera pallida originated in South America [3] and was introduced into Europe in the 19th century with wild potato material used for resistance breeding against late blight. It is widely distributed in Europe and in regions that have imported seed potato from Europe [4]. Yield losses in excess of 50% have been reported and the lack of major gene resistance for G. pallida, coupled to the increasing legislative restrictions on the use of nematicides, mean that new control strategies are required
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