Host-regulated gene expression in plant parasitic nematodes

Plant parasitic nematodes are major economic pests, causing significant yield losses in crop plants worldwide. These nematodes modify or degrade cell wall components to facilitate host entry, migration, and in the case of sedentary endoparasites, feeding site formation. Previous research has demonstrated that Pratylenchus coffeae exhibits host-specific gene expression of cell wall-degrading enzymes when exposed to various host root exudates. This research aimed to investigate whether or not other plant parasitic nematodes exhibit similar capabilities. Similar genes encoding cell wall-degrading enzymes featuring signal peptides, cellulase catalytic domains, and sometimes cellulose binding domains were identified in Globodera pallida and Meloidogyne incognita. Initial exposure to root exudates induced transcriptional responses of these genes in both species, accompanied by behavioural modifications. Subsequent RNA-seq analysis revealed host-specific gene expression patterns in G. pallida and M. incognita when exposed to root exudates from different host and non-host plants. Notably, responses in M. incognita were unique and there was limited overlap in the genes that were up- or down-regulated in response to each root exudate. Conversely, G. pallida displayed a strong response to its preferred host, potato, but not to other plants. Specifically, 1,412 were differentially expressed upon exposure to potato root exudate, compared to only 12 and 4 genes in response to maize and carrot root exudates, respectively. In contrast, M. incognita exhibited responses to a variety of root exudates. Spatial expression of a subset of up-regulated genes was revealed to be in the pharyngeal glands and amphids of both G. pallida and M. incognita, suggesting potential roles as effectors. Successful gene silencing using RNAi resulted in reduced parasitic success in both nematode species. The results from this research advances our understanding of the molecular strategies employed by G. pallida and M. incognita during plant parasitism, offering insights into their adaptability.