A novel chorismate mutase effector secreted from root-knot nematode Meloidogyne enterolobii manipulates plant immunity to promote parasitism1

Meloidogyne spp. is an economically important plant-parasitic nematode distributed worldwide. To fight with host immune system for successful parasitism, plant parasitic nematodes secrete effectors to promote infection. In this study, we identified one chorismate mutase (CM) effector from M. enterolobii, named Me-CM. Spatial and temporal expression assays exhibited Me-cm is expressed in esophageal glands and up-regulated at parasitic-stage juveniles. Me-CM affects the pathogenicity of M. enterolobii based on the reduced infection rate, number of galls, egg masses, eggs per mass and multiplication rate collected from RNA silencing experiments. We showed that Me-CM localized in the cytoplasm and nucleus of plant cells and decreased the expression level of the marker gene PR1 of salicylic acid (SA) pathway. Besides, constitutive expression of Me-cm in Arabidopsis thaliana significantly reduced salicylic acid concentration. These results suggested that M. enterolobii may secrete effector Me-CM to fight with plant immune systems via regulating SA signaling pathway when interacting with host plants, ultimately facilitating parasitism.