The root-knot nematode effectorMi2G02 hijacks a host plant trihelix transcription factor to promote nematode parasitism

Root-knot nematodes(RKNs)cause huge agricultural losses every year.They secrete a repertoire of effectors to facilitate parasitism through the induction of plant-derived giant feeding cells,which serve as their sole source of nutrients.However,the mode of action of these effectors and their targeted host pro-teins remain largely unknown.In this study,we investigated the role of the effector Mi2G02 in Meloidogyne incognita parasitism.Host-derived Mi2G02 RNA interference in Arabidopsis thaliana affected giant cell development,whereas ectopic expression of Mi2G02 promoted root growth and increased plant sus-ceptibility to M.incognita.We used various combinations of approaches to study the specific interactions between Mi2G02 and A.thaliana GT-3a,a trihelix transcription factor.GT-3a knockout in A.thaliana affected feeding-site development,resulting in production of fewer egg masses,whereas GT-3a overex-pression in A.thaliana increased susceptibility to M.incognita and also root growth.Moreover,we demon-strated that Mi2G02 plays a role in maintaining GT-3a protein stabilization by inhibiting the 26S proteasome-dependent pathway,leading to suppression of TOZ and RAD23C expression and thus promoting nematode parasitism.This work enhances our understanding of how a pathogen effector manipulates the role and regulation of a transcription factor by interfering with a proteolysis pathway to reprogram gene expression for development of nematode feeding cells.