Abstract
Summary Evidence is emerging that plant‐parasitic nematodes can secrete effectors to interfere with the host immune response, but it remains unknown how these effectors can conquer host immune responses. Here, we depict a novel effector, MjTTL5, that could suppress plant immune response.Immunolocalization and transcriptional analyses showed that MjTTL5 is expressed specifically within the subventral gland of Meloidogyne javanica and up‐regulated in the early parasitic stage of the nematode. Transgenic Arabidopsis lines expressing MjTTL5 were significantly more susceptible to M. javanica infection than wild‐type plants, and vice versa, in planta silencing of MjTTL5 substantially increased plant resistance to M. javanica.Yeast two‐hybrid, coimmunoprecipitation and bimolecular fluorescent complementation assays showed that MjTTL5 interacts specifically with Arabidopsis ferredoxin : thioredoxin reductase catalytic subunit (AtFTRc), a key component of host antioxidant system. The expression of AtFTRc is induced by the infection of M. javanica. Interaction between AtFTRc and MjTTL could drastically increase host reactive oxygen species‐scavenging activity, and result in suppression of plant basal defenses and attenuation of host resistance to the nematode infection.Our results demonstrate that the host ferredoxin : thioredoxin system can be exploited cunningly by M. javanica, revealing a novel mechanism utilized by plant–parasitic nematodes to subjugate plant innate immunity and thereby promoting parasitism.
Highlights
Root-knot nematodes (RKNs), that is Meloidogyne spp., are one family of the most devastating plant-parasitic nematodes (PPNs), infecting > 3000 plant species from diverse plant families worldwide, which results in c. $70 billion worth of economic loss every year (Caboni et al, 2012)
The genes from M. incognita and R. similis were designated here as MiTTL5 and RsTTL5, and MjTTL5 from M. javanica was obtained by homology-based PCR and characterized further in this study
Independent homozygous lines was confirmed by RT-PCR and western blot (Fig. S8). The susceptibility of these transgenic Arabidopsis lines to nematode infection was determined, and the results showed that all three transgenic lines were significantly (P < 0.05) more susceptible to M. javanica infection than wildtype Arabidopsis, as evidenced by the statistically significant higher number of females inside the roots at 42 dpi (Fig. 3a)
Summary
Root-knot nematodes (RKNs), that is Meloidogyne spp., are one family of the most devastating plant-parasitic nematodes (PPNs), infecting > 3000 plant species from diverse plant families worldwide, which results in c. $70 billion worth of economic loss every year (Caboni et al, 2012). Root-knot nematodes (RKNs), that is Meloidogyne spp., are one family of the most devastating plant-parasitic nematodes (PPNs), infecting > 3000 plant species from diverse plant families worldwide, which results in c. $70 billion worth of economic loss every year (Caboni et al, 2012). RKNs are obligate biotrophic nematodes that infect plant roots and get essential nutrients from specialized multinucleate feeding cells known as giant cells. Similar to other soilborne pathogens, RKNs are very hard to control. To develop new and environmentally safe disease control strategies, it is essential to understand their parasitic mechanisms and how they interact with host plants. Previous studies on bacterial and fungal pathogens have contributed significantly to the understanding of plant defense responses. Plants commonly possess two major types of resistance mechanisms against infection by pathogens and parasites
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