Plant parasitic cyst nematodes respond to viral infection through siRNA activation

Plant parasitic nematodes (PPN) cause yield losses to diverse important crop species and counteractive measures are only partially successful. Recently the first viruses that infect PPN were discovered, presenting new research opportunities to understand and halt PPN. A critical step in this process is to identify how PPN respond to viruses. Here, two PPN species, Globodera rostochiensis and Heterodera schachtii, were used to study PPN-virus interactions. Viral discovery based on bioinformatic analyses indicated three putative viral genomes (a Toti-like, Xinzhao-like and Picorna-like virus) present in G. rostochiensis and five putative viral genomes (a Bunya-like, Tobamo-like, Picorna-like and two Nyami-like viruses) in H. schachtii. A genome composition analysis and RT-qPCR data confirmed that these viruses infect the nematodes and not their host plants. Then antiviral RNAi activity was detected in both H. schachtii and G. rostochiensis using small RNA sequencing. For G. rostochiensis two distinct genotypes were investigated. These strongly differed in their RNAi response: Ro5-line 22 produced roughly 40 times more antiviral siRNAs than Ro1-line 19. Future research into molecular understanding of PPN-virus interactions will aid to create tools for PPN gene delivery or to use PPN viruses in a biocontrol setting.