Abstract
The chrysanthemum foliar nematode (CFN), Aphelenchoides ritzemabosi, is a migratory, plant-parasitic nematode that is widely distributed and infects the aboveground parts of many plants. The fatty acid- and retinoid-binding proteins (FAR) are nematode-specific proteins that are involved in the development, reproduction, and infection of nematodes and are secreted into the tissues to disrupt the plant defense reaction. In this study, we obtained the full-length sequence of the FAR gene (Ar-far-1) from CFN, which is 727 bp and includes a 546 bp ORF that encodes 181 amino acids. Ar-FAR-1 from CFN has the highest sequence similarity to Ab-FAR-1 from A. besseyi, and they are located within the same branch of the phylogenetic tree. Fluorescence-based ligand-binding analysis confirmed that recombinant Ar-FAR-1 was bound to fatty acids and retinol. Ar-far-1 mRNA was expressed in the muscle layer, intestine, female genital system, and egg of CFN, and more highly expressed in females than in males among the four developmental stages of CFN. We demonstrated that the reproduction number and infection capacity of CFN decreased significantly when Ar-far-1 was effectively silenced by in vitro RNAi. Ar-far-1 plays an important role in the development, reproduction, infectivity, and pathogenesis of CFN and may be used as an effective target gene for the control of CFN. The results provide meaningful data about the parasitic and pathogenic genes of CFN to study the interaction mechanism between plant-parasitic nematodes and hosts.
Highlights
The chrysanthemum foliar nematode (CFN), Aphelenchoides ritzemabosi, is an obligate ecto- and endoparasite of the aboveground parts of plants [1,2]
It has been demonstrated that the fatty acid- and retinoid-binding (FAR) protein from the root-knot nematode Meloidogyne javanica may adjust expression of lipid, cell wall, and phenylpropanoid-related genes during nematode infection of hosts [11], the FAR protein in M. incognita possibly influenced the ability of nematodes to move [12], and the Rs-far-1 from Radopholus similis was involved in the regulation of allene oxide synthase (AOS) expression in Anthurium thaliana [13]
The blastp program analysis showed that Ar-FAR-1 is homologous to other FARs from other nematodes, with the highest similarity to Ab-FAR-1 from A. besseyi (91% identity, E-value = 9e–115), and includes a conserved domain similar to that in Gp-FAR-1 (Interval = 31–170, E-value = 1.94e–44, Pfam ID PF05823)
Summary
The chrysanthemum foliar nematode (CFN), Aphelenchoides ritzemabosi, is an obligate ecto- and endoparasite of the aboveground parts of plants [1,2]. The fatty acid- and retinoid-binding (FAR) proteins are helix-rich, lipid-binding proteins that are unique to nematodes and may play an important role in acquiring fatty acids and retinoids from the host [8]. After nematodes secrete FAR proteins into the host tissues that they occupy, these FAR proteins may interfere with intercellular lipid signaling to manipulate the defense reactions of the host and could represent potential targets for new nematicides [8,9]. The Gp-FAR-1 from Globodera pallida has been shown to accumulate on the nematode body surface and is thought to interfere with plant lipoxygenase (LOX)-mediated defense signaling [10]. It has been demonstrated that the FAR protein from the root-knot nematode Meloidogyne javanica may adjust expression of lipid-, cell wall-, and phenylpropanoid-related genes during nematode infection of hosts [11], the FAR protein in M. incognita possibly influenced the ability of nematodes to move [12], and the Rs-far-1 from Radopholus similis was involved in the regulation of allene oxide synthase (AOS) expression in Anthurium thaliana [13]
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