Transcriptome Analysis of Meloidogyne javanica and the Role of a C-Type Lectin in Parasitism.

Meloidogyne javanica is one of the most widespread and economically important sedentary endoparasites. In this study, a comparative transcriptome analysis of M. javanica between pre-parasitic second-stage juveniles (Pre-J2) and parasitic juveniles (Par-J3/J4) was conducted. A total of 48,698 unigenes were obtained, of which 18,826 genes showed significant differences in expression ( p < 0.05). In the differentially expressed genes (DEGs) from transcriptome data at Par-J3/J4 and Pre-J2, a large number of unigenes were annotated to the C-type lectin (CTL, Mg01965 ), the cathepsin L-like protease ( Mi-cpl-1 ), the venom allergen-like protein ( Mi-mps-1 ), Map-1 and the cellulase (endo-β-1,4-glucanase). Among seven types of lectins found in the DEGs, there were 10 CTLs. The regulatory roles of Mj-CTL-1 , Mj-CTL-2 and Mj-CTL-3 in plant immune responses involved in the parasitism of M. javanica were investigated. The results revealed that Mj-CTL-2 could suppress programmed cell death (PCD) triggered by Gpa2/RBP-1 and inhibit the flg22-stimulated ROS burst. In situ hybridization and developmental expression analyses showed that Mj-CTL-2 was specifically expressed in the subventral gland of M. javanica , and its expression was up-regulated at Pre-J2 of the nematode. In addition, in planta silencing of Mj-CTL-2 substantially increased the plant resistance to M. javanica . Moreover, yeast co-transformation and bimolecular fluorescence complementation assay showed that Mj-CTL-2 specifically interacted with the Solanum lycopersicum catalase, SlCAT2 . It was demonstrated that M. javanica could suppress the innate immunity of plants through the peroxide system, thereby promoting parasitism.