Getting to the root of neuronal signalling in plant-parasitic nematodes using RNA interference

Abstract

A variety of genes expressed in preparasitic second-stage juveniles (J2) of plant-parasitic nematodes appear to be vulnerable to RNA interference (RNAi) in vitro by coupling double-stranded (ds)RNA soaking with the artificial stimulation of pharyngeal pumping. Also, there is mounting evidence that the in planta generation of nematode-specific double-stranded RNAs (dsRNAs) has real utility in the control of these pests. Although neuronally-expressed genes in Caenorhabditis elegans are commonly refractory to RNAi, we have discovered that neuronally-expressed genes in plant-parasitic nematodes are highly susceptible to RNAi and that silencing can be induced by simple soaking procedures without the need for pharyngeal stimulation. Since most front-line anthelmintics that are used for the control of nematode parasites of animals and humans act to disrupt neuromuscular coordination, we argue that intercellular signalling processes associated with neurons have much appeal as targets for transgenic plant-based control strategies for plant-parasitic nematodes. FMRFamide-like peptides (FLPs) are a large family of neuropeptides which are intimately associated with neuromuscular regulation, and our studies on flp gene function in plant-parasitic nematodes have revealed that their expression is central to coordinated locomotory activities. We propose that the high level of conservation in nervous systems across nematodes coupled with the RNAi-susceptibility of neuronally-expressed genes in plant-parasitic nematodes provides a valuable research tool which could be used to interrogate neuronal signalling processes in nematodes.

Induced knockdown of Mg-odr-1 and Mg-odr-3 perturbed the host seeking behavior of Meloidogyne graminicola in rice

“…Collectively, all these results suggest that RNAi-induced targeted downregulation of Mg-odr-1 and Mg-odr-3 noticeably perturbed the M. graminicola chemotaxis behavior, establishing the crucial role of Mg-odr-1 and Mg-odr-3 in Meloidogyne graminicola olfaction and nociception mechanism. The adaptive olfactory responses (ability to selectively discriminate different compounds) of PPNs such as M. incognita and Globodera pallida towards different phytochemicals such as sugars, amino acids, hormones, phenolics and organic acids have been described in various studies [ [50] , [51] , [52] , [53] ].…”

Attraction of second‐stage juveniles of Meloidogyne species to fluopyram

“…[11][12][13] Carbon dioxide has long been suggested as an attractant, [13][14][15][16][17][18] but its application is difficult due to its gas phase, rapid diffusion in the soil, and emission into the air. Some of the other attractants discovered in the last 15 years for Meloidogyne species are salicylic acid, 19,20 Brønsted-Lowry acids such as acetic and propionic acids, 21 potassium nitrate (KNO 3 ), 22 1,3-diaminopropane, cadaverine and putrescine in root exudates of tomato and soybean, 23 and carbohydrates with L-galactose sidechains in flaxseed mucilage, 24 among others. However, the attractiveness of most of these compounds has not been tested in the soil.…”

Root-knot nematode chemotaxis is positively regulated by l -galactose sidechains of mucilage carbohydrate rhamnogalacturonan-I

“…Root exudates from soy, tomato, Medicago, and pea are known to attract RKN ( 3 , 8 – 10 ). Specifically, plant metabolites including phytohormones (salicylic acid, gibberellic acid, and indole-3-acetic acid), amino acids (arginine and lysine), organic acids (vanillic acid, tannic acid, and lauric acid), and other compounds (organic diamines, mannitol, and flavonoids) have been demonstrated to attract RKN ( 11 – 13 ). However, compounds that are found in most plants are probably not very useful for deciphering RKN’s host specificities because they are more likely to function as general cues that guide RKN to any plants in the vicinity.…”