These cells become polynucleate and may be more than 300 times larger than normal cells. These cells are produced from about half a dozen vascular root cells, which undergo repeated nuclear divisions without cell division. The RKN feeding site consists of so-called “giant cells” ( Figure 1A). Mobile preparasitic juveniles (J2) penetrate the host root, traveling toward the vascular cylinder, where they become sedentary, triggering the formation of an unusual feeding site. (sugar beet, soybean, or cereal CN), each of which causes huge yield losses on its host.īoth CN and RKN are sedentary endoparasites and obligate biotrophs. By contrast, CN tend to specialize on a particular crop and form two common genera: Globodera spp. RKN from the Meloidogyne genus are found throughout the world and are extremely polyphagous, infecting thousands of plant species, including both monocotyledons and eudicotyledons ( Blok et al., 2008). Root-knot nematodes (RKN) and cyst nematodes (CN) are the most widely studied PPN, as these two groups are the most damaging to crop plants ( Singh et al., 2013). Plant-parasitic nematodes (PPN) are microscopic worms that withdraw nutrients from the cytoplasm of cells in the aerial or below-ground parts of plants. A better understanding of the molecular determinants of these biotrophic relationships would enable us to improve the yields of crops infected with parasitic nematodes and to expand our comprehension of root development. Here, we review recent findings on the identification and functional characterization of plant targets of RKN and CN effectors. Within the plant cell or in the apoplast, effectors associate with specific host proteins, enabling them to hijack important processes for cell morphogenesis and physiology or immunity. Both RKN and CN secrete effector proteins that are synthesized in the oesophageal glands and delivered to the appropriate cell in the host plant via a syringe-like stylet, triggering the ontogenesis of the feeding structures. ![]() These dramatically modified host cells act as metabolic sinks from which the nematode withdraws nutrients throughout its life, and they are thus essential for nematode development. CN infection leads to the fusion of several root cells into a unique syncytium. They are surrounded by small dividing cells and they form a new organ within the root known as a root knot or gall. The giant cells result from nuclear divisions of vascular cells without cytokinesis. RKN and CN spend most of their life cycle in plant roots, in which they induce the formation of multinucleate hypertrophied feeding cells, called “giant cells” and “syncytia,” respectively. ![]() and Globodera spp.) cause considerable damage to agricultural crops. Sedentary endoparasitic nematodes, such as root-knot nematodes (RKN Meloidogyne spp.) and cyst nematodes (CN Heterodera spp. ![]() Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique, Institut Sophia Agrobiotech, Université Côte d’Azur, Sophia Antipolis, France.Joffrey Mejias, Nhat My Truong †, Pierre Abad, Bruno Favery and Michaël Quentin *
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