MiPDCD6 effector suppresses host PAMP‐triggered immunity to facilitate Meloidogyne incognita parasitism in tomato

Abstract

AbstractPlant‐parasitic nematodes secrete several effectors that suppress host PAMP‐triggered immunity for successful parasitism. Here, we have characterized a novel effector from the root‐knot nematode Meloidogyne incognita, named MiPDCD6. The MiPDCD6 gene is expressed in the subventral oesophageal glands and is upregulated in the mid‐stages of M. incognita parasitism in plants. Tobacco rattle virus‐induced gene silencing (VIGS) targeting MiPDCD6 attenuated M. incognita parasitism. Compared with the control, in tomato plants with MiPDCD6 VIGS, the numbers of root knots were significantly reduced by 46.3%, giant cell development was delayed by 7 days (as shown by the improved paraffin section technique), and the expression levels of both PR‐1 and PR‐5 tomato genes were significantly higher, as shown by reverse transcription‐PCR. Although MiPDCD6 lacks a classic signal peptide for secretion at its N‐terminus, results of immunofluorescence localization showed that MiPDCD6 could be secreted by M. incognita, transported and function in giant cells of tomato. Transient expression of MiPDCD6 in Nicotiana benthamiana suppressed cell death triggered by BAX and callose deposition induced by PIAvh142, inhibited reactive oxygen species accumulation induced by flg22, and reduced expression of PR1 and PR5, which are marker genes of the salicylic acid (SA)‐mediated immune signalling pathway. These results indicate that M. incognita deploys MiPDCD6 to suppress SA‐mediated plant immunity to promote its parasitism.