The role of rhizosphere signalling in the plant-cyst nematode interaction

The parasitic Potato Cyst Nematode (PCN) species Globodera pallida and G. rostochiensis are pests that can infect Solanaceae crops and can cause considerable losses in agriculture. PCN eggs can remain dormant in the soil for up to decades, and hatch only if they perceive a host-specific cue. One of these so-called Hatching Factors (HF) is the triterpenoid solanoeclepin A (solA), which is produced by potato and tomato. This thesis zooms in along the axis of the interaction between plant and nematode. First, the effect of solA on the plant is studied using RNAseq. Treatment of tomato and Arabidopsis with solA downregulates immune- and hypoxia-related transcripts, as well as ethylene biosynthesis and signalling, and promotes growth. Next, an analytical method for the detection of solA in root exudates is presented. This method is used to measure solA in root exudates of a range of potato genotypes, and using machine learning, metabolomics and hatching assays, hitherto unknown new HF are identified. Lastly, the perception of HF in PCN is studied. The dauer hypothesis, stating that the C. elegans dauer state was necessary for the evolution of several forms of parasitism, is explored for the parasitic nematode species in Clade 12, to which PCN belongs. Furthermore, using RNAseq, it is shown that dauer specific transcripts are differentially expressed upon PCN hatching. Furthermore, hatching is inhibited through chemical inhibition of the dauer signalling pathway, and PCN can produce dafachronic acid endogenously, which marks the endpoint of the pathway.