Nematode Effector Proteins: Targets and Functions in Plant Parasitism

Plant-parasitic nematodes are obligate parasites that withdraw nutrients from the cytoplasm of living plant cells. The most damaging species worldwide are sedentary endoparasites that induce the differentiation of root cells into unique multinucleate and metabolically hyperactive enlarged feeding cells, called syncytia in the case of cyst nematodes or giant-cells in the case of root-knot nematodes. These nematodes use a hollow, protrusible feeding stylet to inject the secretions produced in three esophageal gland cells within the plant tissues throughout parasitism. The success of infection relies on efficient root invasion, re-programming of plant cells into feeding cells and evasion from plant defenses to maintain the host-parasite relationship for 3-6 weeks until the nematode's life cycle is completed. Effectors involved in these three functions have been identified that denote most remarkable evolution adaptations such as multiple lateral gene transfers and plant ligand mimicry to establish successful interactions with plants.