Fatty Acid-and Retinol-Binding Protein, Mj-FAR-1 Induces Tomato Host Susceptibility to Root-Knot Nematodes

Abstract

Plant-parasitic nematodes produce at least one structurally unique class of small helix-rich retinol- and fatty-acid-binding proteins that have no counterparts in their plant hosts. Herein we describe a protein of the plant-parasitic root-knot nematode Meloidogyne javanica, which is a member of the nematode-specific fatty-acid- and retinol-binding (Mj-FAR-1) family of proteins. The mj-far-1 mRNA was detected through M. javanica pre-parasitic J2s, migratory and sedentary parasitic stages by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). Immunolocalization assays demonstrate that the FAR protein of Meloidogyne is secreted during sedentary stages, as evidenced by the accumulation of FAR at the nematode cuticle surface and along the adjacent host root tissues. Tomato roots constitutively expressing mj-far-1 demonstrated an increased susceptibility to root-knot nematodes infection as observed by accelerated gall induction and expansion, accompanied by a higher percentage of nematodes developing into mature females compared to control roots. RNA interference assays that expressed double-stranded RNA complementary to mj-far-1 in transgenic tomato lines specifically reduced nematode infection levels. Histological analysis of nematode-infested roots indicated that in roots overexpressing mj-far-1, galls contained larger feeding cells and might support a faster nematode development and maturation. Roots overexpressing mj-far-1 suppressed jasmonic acid responsive genes such as the proteinase inhibitor (Pin2) and γ-thionin, illustrating the possible role of Mj-FAR-1 in manipulating the lipid based signaling in planta. This data, suggests that Meloidogyne FAR might have a strategic function during the interaction of the nematode with its plant host. Our study present the first demonstration of an in planta functional characterization and localization of FAR proteins secreted by plant-parasitic nematodes. It provides evidence that Mj-FAR-1 facilitates infection most likely via the manipulation of host lipid-based defenses, as critical components for a successful parasitism by plant-parasitic nematodes.

Characterization of the venom allergen—like protein (vap-1) and the fatty acid and retinol binding protein (far-1) genes in Meloidogyne hispanica

“…However, in contrast with this work, G. pallida and M. javanica FAR-1 proteins have been shown to be highly expressed in the migratory and parasitic J2 with transcription in the nematode surface and also within the adult female body, using immunolocalization studies with the same antiserum (Prior et al 2001;Iberkleid et al 2013). Although M. hispanica far-1 formed a well supported clade (100 %) with M. incognita it showed only 67 % bootstrap with M. javanica which could We also showed in this paper that the localization of Mhi-far-1 is similar to M. incognita FAR protein but differs in M. hispanica in comparison with M. javanica (Bellafiore et al 2008;Iberkleid et al 2013).…”

“…However, FAR proteins clearly distinguished and grouped different nematode species according to their trophic group and nematode parasitism strategy. The highest predicted amino acid identity of Mj-FAR-1 was found amongst M. incognita, M. arenaria and M. hapla and the lowest observed between M. javanica and M. chitwoodi (Iberkleid et al 2013). Although, there is a strong conservation for this group of proteins, M. hapla in this study showed to be the most divergent when compared with M. hispanica, which might account for a particular mode of parasitism adaptation and/or reproduction.…”

“…Animal parasitic allergen genes have been associated with the induction of a host immune response (Chen et al 2010) and the effector Gr-VAP-1, localized in the subventral oesophageal glands of G. rostochiensis pre-parasitic J2, has also been implicated in resistance (Lozano-Torres et al 2012). Using RT-PCR, this study shows that equal expression of MHI-FAR-1 was detected in eggs, J2 and females however, quantitative real time PCR indicates that for M. javanica the lowest level of expression for mj-far-1 transcripts was detected within eggs and the highest in J2 within the first hours after root infection, which suggest a potential role of MJ-FAR during the different parasitic stages (Iberkleid et al 2013). Using in situ hybridization, this work localized the Mhi-far-1 in the subventral oesophageal glands of J2 and the same localization, using different approaches, was identified for a protein similar to the Gp-FAR in the oesophageal glands of M. incognita, another FAR protein of the plant parasitic nematode D. africanus was also identified in the oesophageal glands (Bellafiore et al 2008;Haegeman et al 2009).…”

“…Previous phylogenetic studies demonstrated that FAR homologues from the animal parasitic nematodes O n c h o c e r c a , B r u g i a , Wu c h e r e r i a , L o a , Acanthocheilonema, Ascaris suum, Toxocara canis, and Litomosoides, and the plant-parasitic nematodes G. pallida, G. rostochiensis, M. javanica, M. arenaria, H. schachtii, P. vulnus and R. similis, and the free-living nematode Caenorhabditis elegans were closely related and they all share conserved amino acid sequences in its primary and secondary structures (Prior et al 2001;Garofalo et al 2002;Iberkleid et al 2013). Mj-FAR-1 grouped closely with FARs belonging to other parasitic nematodes (animal, sedentary, and migratory plantparasitic nematodes).…”

“…A study with M. javanica suggests that the MJ-FAR-1 protein has an important role in the infection process. FAR-1 induces susceptibility to RKN through the manipulation of jasmonate-dependent defence response (Iberkleid et al 2013). FAR-1 has also been identified in H. schachtii, M. chitwoodi, M. hapla, M. incognita, P. coffeae and Radopholus similis (Vanholme et al 2006;Bellafiore et al 2008;Jacob et al 2008;Opperman et al 2008;Roze et al 2008;Haegeman et al 2009Haegeman et al , 2011.…”