Knockdown of a mucin‐like gene in Meloidogyne incognita (Nematoda) decreases attachment of endospores of Pasteuria penetrans to the infective juveniles and reduces nematode fecundity

Abstract

Mucins are highly glycosylated polypeptides involved in many host-parasite interactions, but their function in plant-parasitic nematodes is still unknown. In this study, a mucin-like gene was cloned from Meloidogyne incognita (Mi-muc-1, 1125 bp) and characterized. The protein was found to be rich in serine and threonine with numerous O-glycosylation sites in the sequence. Quantitative real-time polymerase chain reaction (qRT-PCR) showed the highest expression in the adult female and in situ hybridization revealed the localization of Mi-muc-1 mRNA expression in the tail area in the region of the phasmid. Knockdown of Mi-muc-1 revealed a dual role: (1) immunologically, there was a significant decrease in attachment of Pasteuria penetrans endospores and a reduction in binding assays with human red blood cells (RBCs), suggesting that Mi-MUC-1 is a glycoprotein present on the surface coat of infective second-stage juveniles (J2s) and is involved in cellular adhesion to the cuticle of infective J2s; pretreatment of J2s with different carbohydrates indicated that the RBCs bind to J2 cuticle receptors different from those involved in the interaction of Pasteuria endospores with Mi-MUC-1; (2) the long-term effect of RNA interference (RNAi)-mediated knockdown of Mi-muc-1 led to a significant reduction in nematode fecundity, suggesting a possible function for this mucin as a mediator in the interaction between the nematode and the host plant.

De novoassembly of thePasteuria penetransgenome reveals high plasticity, host dependency, and BclA-like collagens

“…Pasteuria penetrans gene predictions were interrogated for collagens using Pfam collagen domain (PF01391) and HMMER (v3.1b2) hmmsearch (http://hmmer.org/). Predicted collagens were aligned to contigs and to each other using BLASTn (v2.7.1) [13]. Unique collagen sequence structural models and predicted binding sites were produced using the RaptorX server [41].…”

“…This has prompted the current “Velcro-model” of attachment involving bacterial collagen-like fibres, observable under electron microscopy on the exosporium surface, and nematode cuticle associated mucins [12]. Recently, Phani et al [13] demonstrated that knockdown of a mucin like gene, Mi-muc-1 , reduced cuticular attachment of P. penetrans endospores to M. incognita . However, the exact nature of this host-parasite interaction is not known at the genetic or molecular level.…”

Plant Root-Exudates Recruit Hyperparasitic Bacteria of Phytonematodes by Altered Cuticle Aging: Implications for Biological Control Strategies

“…To date, no cuticle receptor for collagen-like protein binding has been identified, but experiments with Caenorhabditis elegans have identified several mutants (designated srf, bus, and bah) which are involved in building the complex glycoconjugates of the nematode surface coat and which affect microbial pathogenicity Hodgkin, 2005, 2011); one such mutation, bus-4, confers bacterial resistance by the production of altering mucins (Parsons et al, 2014). Interestingly, knockdown of a RKN mucin gene using RNAi with infective juveniles of M. incognita was also found to reduce P. penetrans endospore attachment (Phani et al, 2018) suggesting its involvement, but similar RNAi knockdown experiments targeting another gene (Mi-FAR-1) also affected endospore adhesion to the cuticle (Phani et al, 2017). This suggest that adhesion of endospores is the result of a complex set of cuticular interactions, and it is highly likely that the molecules responsible for the variation exhibited by endospore attachment FIGURE 5 | Cartoon representing a theoretical model of the interactions between plant root exudates (arrows) and the cuticle of nematodes: blue arrow represents exudates that recruit Pasteuria endospores to the blue nematodes by a reduction in cuticular aging, they also decruit endospore adhesion to the green nematodes by increased cuticular aging; similarly, the green arrow represents exudates that decrease cuticula r aging to the green nematodes thereby recruiting green endospore attachment and increase cuticular aging in the blue nematodes and decruit endospore adhesion; exudates that decruit endospore adhesion maintain those spores in the Pasteuria spore bank to control nematodes to which both spores types can attach and can infect both host plants represented by the blue/green stripped nematodes producing an arms in the effects of root exudates (not to scale).…”

A transcriptomic snapshot of early molecular communication between Pasteuria penetrans and Meloidogyne incognita

“…RNAi induced in vitro inhibition of both these transcripts reduced the endospore attachment on nematode surface. Silencing fructose bisphosphate aldolase might have resulted in accumulation of sugar on the specific carbohydrate recognition sites on nematode mucin-like glycoprotein that binds to Pasteuria endospores [25, 85], thereby leading to reduction in attachment of endospores. Additionally, inhibition of glucosyl transferase may also result in mis-folding of the native glycoprotein molecules, thus resulting in decreased endospore attachment.…”