A multi-omics approach reveals that the plant-parasitic nematode Globodera pallida can produce the phytohormone auxin IAA

The phytohormone auxin plays a crucial role in the development of so-called syncytia induced by cyst nematodes upon feeding on plant roots. However, it is unknown whether nematode-derived auxin contributes to plant parasitism by cyst nematodes. To do so, plantparasitic nematodes should be able to produce and release auxin into the environment. Here, we investigated whether this is the case. Mass-spectrometry analyses show that the cyst nematode Globodera pallida is able to synthesize and release the auxin indole-3-acetic acid (IAA) and indicates that its biosynthesis can be stimulated by root diffusate. Using a collection of known auxin biosynthesis genes from well-studied pathways in bacteria and plants we revealed that in the genome of G. pallida candidate genes are present for five major biosynthesis pathways which could be responsible for auxin production. RNA-seq data supported the genomic analysis and revealed the upregulation of various candidate biosynthesis genes during parasitic life stages of the nematode, suggesting a possible role in plant parasitism. However, genomic analysis within the phylum Nematoda showed that the potential auxin biosynthesis genes are wide-spread and also occur in bacterivorous, fungivorous, entomopathogenic and animal-parasitic nematodes. Therefore, our data show that G. pallida is able to synthesize and release auxin into the environment, but that potential auxin biosynthesis pathways are not unique for plant-parasitic nematodes. So, auxin biosynthesis may play a broader role in the life history of nematodes. However, a more specialized role for nematode-produced auxin in plant parasitism cannot be excluded and needs further investigation.