Molecular and biochemical characterization of the β-1,4-endoglucanase gene Mj-eng-3 in the root-knot nematode Meloidogyne javanica

- Mj-eng-3 was expressed in the subventral glands of M. javanica juveniles.
- The highest transcriptional level of Mj-eng-3 occurred in pre-J2 stage.
- High expression level of Mj-eng-3 persisted in the early par-J2 stage.
- MJ-ENG-3 exhibited cellulase activity.
- In planta RNAi silencing of Mj-eng-3 reduced the parasitism ability of M. javanica.

This study describes the molecular and biochemical characterization of the β-1,4-endoglucanase gene (Mj-eng-3) from the root knot nematode Meloidogyne javanica. A 2156-bp genomic DNA sequence of Mj-eng-3 containing six introns was obtained. Mj-eng-3 was localized in the subventral esophageal glands of M. javanica juveniles by in situ hybridization. Real-time RT-PCR assay showed that the highest transcriptional level of Mj-eng-3 occurred in pre-parasitic second-stage juveniles, and this high expression persisted in parasitic second-stage juveniles. Recombinant MJ-ENG-3 degraded carboxymethylcellulose and optimum enzyme activity at 40 °C and pH 8.0. EDTA, Mg2+, Mn2+, Ca2+, Co2+, and Cu2+ did not affect the activity of MJ-ENG-3; however, Zn2+ and Fe2+ inhibited MJ-ENG-3 enzyme activity. In planta Mj-eng-3 RNAi assay displayed a reduction in the number of nematodes and galls in transgenic tobacco roots. These results suggested that MJ-ENG-3 could be secreted by M. javanica to degrade the cellulose of plant cell walls to facilitate its entry and migration during the early stages of parasitism.