A Nematode Effector, MiMSP8, Targets U2AF, a Subunit of a Splicing Factor Involved in Host pre‐mRNA Splicing, Thereby Promoting Parasitism

ABSTRACT Root‐knot nematodes secrete effectors into plant cells to facilitate parasitism. A candidate effector, MiMSP8, of Meloidogyne incognita has been shown to localise within the nucleus when transiently expressed in Nicotiana benthamiana leaf cells, but its role is still unknown. We demonstrate that the MiMSP8 protein is expressed in the dorsal gland of M. incognita juveniles and it can also be detected within giant cells induced by nematodes. Silencing of MiMSP8 impairs nematode parasitism while overexpression of MiMSP8 increases susceptibility to nematode infection. MiMSP8 interacts with SlU2AF35, the small subunit of the U2 snRNP auxiliary factor (U2AF) in tomato. This interaction competes with SlU2AF65 for binding to SlU2AF35, thereby disrupting the formation of heterodimers of the key splicing factor U2AF. Overexpression of MiMSP8 in tomato hairy roots leads to genome‐wide alternative splicing changes involved in multiple biological processes. MiMSP8 interferes with the binding between SlU2AF35 and pre‐mRNAs of a subset of genes. Silencing SlU2AF35 results in abnormal gene splicing in plants and increases their sensitivity to nematode parasitism. Collectively, our findings reveal that M. incognita deploys a nuclear localised effector to target a key component of the spliceosome and disrupt the splicing of plant pre‐mRNA to promote parasitism.