Dissecting interactions between root-knot nematode effectors and lipid signaling involved in plant defense

Root-knot nematodes, Meloidogynespp., are extremely destructive pathogens with a cosmopolitan distribution and a host range that affects most crops. Safety and environmental concerns related to the toxicity of nematicides along with a lack of natural resistance sources threaten most crops in Israel and the U.S. This emphasizes the need to identify genes and signal mechanisms that could provide novel nematode control tactics and resistance breeding targets. The sedentary root-knot nematode (RKN) Meloidogynespp. secrete effectors in a spatial and temporal manner to interfere with and mimic multiple physiological and morphological mechanisms, leading to modifications and reprogramming of the host cells' functions, resulted in construction and maintenance of nematodes' feeding sites. For successful parasitism, many effectors act as immunomodulators, aimed to manipulate and suppress immune defense signaling triggered upon nematode invasion. Plant development and defense rely mainly on hormone regulation. Herein, a metabolomic profiling of oxylipins and hormones composition of tomato roots were performed using LC-MS/MS, indicating a fluctuation in oxylipins profile in a compatible interaction. Moreover, further attention was given to uncover the implication of WRKYs transcription factors in regulating nematode development. In addition, in order to identify genes that might interact with the lipidomic defense pathway induced by oxylipins, a RNAseq was performed by exposing M. javanicasecond-stage juveniles to tomato protoplast, 9-HOT and 13-KOD oxylipins. This transcriptome generated a total of 4682 differentially expressed genes (DEGs). Being interested in effectors, we seek for DEGs carrying a predicted secretion signal peptide. Among the DEGs including signal peptide, several had homology with known effectors in other nematode species, other unknown potentially secreted proteins may have a role as root-knot nematodes' effectors which might interact with lipid signaling. The molecular interaction of LOX proteins with the Cyst nematode effectors illustrate the nematode strategy in manipulating plant lipid signals. The function of several other effectors in manipulating plant defense signals, as well as lipids signals, weakening cell walls, attenuating feeding site function and development are still being studied in depth for several novel effectors. As direct outcome of this project, the accumulating findings will be utilized to improve our understanding of the mechanisms governing critical life-cycle phases of the parasitic M. incognita RKN, thereby facilitating design of effective controls based on perturbation of nematode behavior—without producing harmful side effects. The knowledge from this study will promote genome editing strategies aimed at developing nematode resistance in tomato and other nematode-susceptible crop species in Israel and the United States.