Genus-level evolutionary relationships of FAR proteins reflect the diversity of lifestyles of free-living and parasitic nematodes

Abstract

Background Nematodes are a widespread and diverse group comprising free-living and parasitic species, some of which have major detrimental effects on crops, animals, and human health. Genomic comparisons of nematodes may help reveal the genetic bases for the evolution of parasitic lifestyles. Fatty acid and retinol-binding proteins (FARs) are thought to be unique to nematodes and play essential roles in their development, reproduction, infection, and possibly parasitism through promoting the uptake, transport, and distribution of lipid and retinol. However, the evolution of FAR family proteins across the phylum Nematoda remains elusive. Results We report here the evolutionary relationship of the FAR gene family across nematodes. No FAR was found in Trichocephalida species and Romanomermis culicivorax from Clade I, and FAR could be found in species from Clades III, IV, and V. FAR proteins are conserved in Clade III species and separated into three clusters. Tandem duplications and high divergence events lead to variable richness and low homology of FARs in Steinernema of Clade IVa, Strongyloides of Clade IVb, and intestinal parasitic nematodes from Clades Vc and Ve. Moreover, different richness and sequence variations of FARs in pine wood, root-knot, stem, and cyst nematodes might be determined by reproduction mode or parasitism. However, murine lungworm Angiostrongylus and bovine lungworm Dictyocaulus viviparus from Clade Vd have only 3–4 orthologs of FAR. RNA-seq data showed that far genes, especially far-1 and far-2, were highly expressed in most nematodes. Angiostrongylus cantonensis FAR-1 and FAR-3 have low sequence homology and distinct ligand-binding properties, leading to differences in the cavity volume of proteins. These data indicate that FAR proteins diverged early and experienced low selective pressure to form genus-level diversity. The far genes are present in endophyte or root-colonized bacteria of Streptomyces, Kitasatospora sp., Bacillus subtilis, and Lysobacter, suggesting that bacterial far genes might be derived from plant-parasitic nematodes by horizontal gene transfer. Conclusions Data from these comparative analyses have provided insights into genus-level diversity of FAR proteins in the phylum Nematoda. FAR diversification provides a glimpse into the complicated evolution history across free-living and parasitic nematodes.

Parasitic nematode fatty acid- and retinol-binding proteins compromise host immunity by interfering with host lipid signaling pathways

“…Phenoloxidase is the catalyst for the oxidation of mono- and diphenols to orthoquinones, which form polymers with melanin non-enzymatically, during which ROS is produced [ 24 , 35 ]. Since the family of FAR proteins is highly conserved among many nematode species it is important to understand whether FARs elicit their immunomodulatory effects in similar ways ( Table 1 ) [ 35 ]. Slight differences between the effects of the two Sc-FARs are apparent in flies challenged with X .…”

Transcriptomic Analysis of Steinernema Nematodes Highlights Metabolic Costs Associated to Xenorhabdus Endosymbiont Association and Rearing Conditions

“…FAR proteins have been described as unique proteins specific to nematodes (Garofalo et al, 2003). Although, recently horizontal transfer of FAR genes in bacteria genomes has been suggested within Kitasatospora, Bacillus, Lysobacter, and Streptomyces (Yuan et al, 2021). The FAR proteins are intriguing and despite early investigations on their ligand-binding propriety, very little is known regarding their function in vivo (Garofalo et al, 2003).…”

“…The FAR proteins have been identified in numerous nematodes genomes and that their numbers are highly variable. For example, eight were identified in C. elegans genome and 19 in Pristionchus pacificus genome, and in parasitic-nematodes, eight in Necator americanus, 1-4 in Globodera, 18-30 in Ancylostoma (Garofalo et al, 2003;Dieterich et al, 2008;Yuan et al, 2021).…”

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“…Rather, it is dependent upon activation of prophenoloxidase (proPO), which is a proenzyme that is cleaved by prophenoloxidase activating enzyme (PPAE) to its active form phenoloxidase (PO). Phenoloxidase is the catalyst for the oxidation of mono-and diphenols to orthoquinones, which form polymers with melanin non-enzymatically, during which ROS is produced [24,35]. Since the family of FAR proteins is highly conserved among many nematode species it is important to understand whether FARs elicit their immunomodulatory effects in similar ways (Table 1) [35].…”

“…Phenoloxidase is the catalyst for the oxidation of mono-and diphenols to orthoquinones, which form polymers with melanin non-enzymatically, during which ROS is produced [24,35]. Since the family of FAR proteins is highly conserved among many nematode species it is important to understand whether FARs elicit their immunomodulatory effects in similar ways (Table 1) [35]. Slight differences between the effects of the two Sc-FARs are apparent in flies challenged with X. innexi, where FAR-2 expressing flies given a 25,000 CFU dose did not do significantly worse than the control flies, as well as the recombinant studies and AMP production, pointing to a potential mechanistic specificity of FARs.…”