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

Abstract 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, plant-parasitic 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 5 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.