Host-Induced Silencing of Two Pharyngeal Gland Genes Conferred Transcriptional Alteration of Cell Wall-Modifying Enzymes of Meloidogyne incognita vis-à-vis Perturbed Nematode Infectivity in Eggplant

Abstract

The complex parasitic strategy of Meloidogyne incognita appears to involve simultaneous expression of its pharyngeal gland-specific effector genes in order to colonize the host plants. Research reports related to effector crosstalk in phytonematodes for successful parasitism of the host tissue is yet underexplored. In view of this, we have used in planta effector screening approach to understand the possible interaction of pioneer genes (msp-18 and msp-20, putatively involved in late and early stage of M. incognita parasitism, respectively) with other unrelated effectors such as cell-wall modifying enzymes (CWMEs) in M. incognita. Host-induced gene silencing (HIGS) strategy was used to generate the transgenic eggplants expressing msp-18 and msp-20, independently. Putative transformants were characterized via qRT-PCR and Southern hybridization assay. SiRNAs specific to msp-18 and msp-20 were also detected in the transformants via Northern hybridization assay. Transgenic expression of the RNAi constructs of msp-18 and msp-20 genes resulted in 43.64–69.68% and 41.74–67.30% reduction in M. incognita multiplication encompassing 6 and 10 events, respectively. Additionally, transcriptional oscillation of CWMEs documented in the penetrating and developing nematodes suggested the possible interaction among CWMEs and pioneer genes. The rapid assimilation of plant-derived carbon by invading nematodes was also demonstrated using 14C isotope probing approach. Our data suggests that HIGS of msp-18 and msp-20, improves nematode resistance in eggplant by affecting the steady-state transcription level of CWME genes in invading nematodes, and safeguard the plant against nematode invasion at very early stage because nematodes may become the recipient of bioactive RNA species during the process of penetration into the plant root.

Smart Parasitic Nematodes Use Multifaceted Strategies to Parasitize Plants

“…They have shown that the tomato roots overexpressing Mj-FAR-1 led to the down-regulation of JA responsive genes like proteinase inhibitor (Pin2) and γ-thionin, demonstrating the probable role of Mj-FAR-1 in modulating the lipid based signaling in planta . Very recently in planta silencing of two pioneer genes msp-18 and msp-20 supported lower numbers of M. incognita on transgenic egg plants (Shivakumara et al, 2017 ). Moreover, suppression of these pioneer genes resulted in the down-regulation of cell wall modifying enzymes (CWME), i.e., Mi-pg-1 and Mi-pel, in females developing in the best transgenic events as compared to the control.…”

Cross-kingdom RNA trafficking and environmental RNAi — nature's blueprint for modern crop protection strategies

“…Such engineered RNA-based communication termed host-induced gene silencing (HIGS) [11,15 ● ] has emerged as a promising strategy for crop protection. A wide range of transgenic crops expressing dsRNAs that are subsequently processed into sRNAs targeting essential and/or pathogenicity genes are more resistant to viruses [16], viroids [17], bacteria [18], fungi [5 ●● ,15 ● ,19,20 ● ], oomycetes [21,22], nematodes [23–25], and insects [26–28,29 ● ]. The broad applicability of the technique supports a basic evolutionary-conserved mechanism of sRNA trafficking.…”

Host-induced gene silencing involves Arabidopsis ESCRT-III pathway for the transfer of dsRNA-derived siRNA

“…Small (s)RNA effectors play a crucial role in the outcome of plant-pathogen interactions [1][2][3][4] and have a great potential for controlling diseases and pests in crop plants [5][6][7][8] A multitude of transgenic crops expressing dsRNAs targeting essential genes through RNAi are more resistant to viruses [9], viroids [10], bacteria [11], fungi [12][13][14][15], oomycetes [16], nematodes [17,18], and insects [19,20]. Host-induced gene silencing (HIGS) involves i. processing of transgenederived dsRNA into small interfering (si)RNAs, ii.…”