Dataset Information

Morphological adjustment in free-living Steinernema feltiae infective juveniles to increasing concentration of Nemafric-BL phytonematicide.

ABSTRACT: Third-stage larvae (L3) of Steinernema feltiae exist as free-living infective juveniles (IJ), with suspended development activities. In contrast, parasitic stages (L1, L2, L4, adult) have mutualistic relations with Xenorhabdus species bacteria, along with unique morphological changes and development inside the cadaver of host insects and/or plant-parasitic nematodes. Commercial IJ strains are tolerant to cucurbitacin-containing phytonematicides, but we have scant information on how morphological adjustments in IJ are achieved. In this study, we investigated the nature of morphological adjustments in commercial S. feltiae IJ strains to Nemafric-BL phytonematicide, which contains cucurbitacin B as active ingredient. Post-72 h exposure to phytonematicide concentration, IJ specimens were fixed on mounting slides. Length (body, excretory pore to anterior end, pharynx, rectum, stoma, tail), diameter (head width, neck base, mid-body, anal body), cuticle thickness and De Man ratios were measured with a computer software programme attached to Omax light microscope. Morphometric data against increasing phytonematicide concentration exhibited either density-dependent quadratic, linear or neutral relations. Increase in body length at low phytonematicide concentration was accompanied by decrease in tail length and pharynx length during muscle contraction when IJ were still alive. After death at high phytonematicide concentration, the opposite morphometric effects ensued due to muscle relaxation. The observed changes in morphometric structures were explained on the basis of morphological adjustments that modulated volumes of pseudocoelom cavity in IJ. The modulation is intended to maintain hydrostatic pressure within permissible upper limits in order to avoid structural damage to internal organs embedded in the pseudocoelom fluids.

SUBMITTER: Mashela PW

PROVIDER: S-EPMC6941822 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Morphological adjustment in free-living Steinernema feltiae infective juveniles to increasing concentration of Nemafric-BL phytonematicide.

Mashela Phatu W PW Shokoohi Ebrahim E Pofu Kgabo M KM

PloS one 20200103 1

Third-stage larvae (L3) of Steinernema feltiae exist as free-living infective juveniles (IJ), with suspended development activities. In contrast, parasitic stages (L1, L2, L4, adult) have mutualistic relations with Xenorhabdus species bacteria, along with unique morphological changes and development inside the cadaver of host insects and/or plant-parasitic nematodes. Commercial IJ strains are tolerant to cucurbitacin-containing phytonematicides, but we have scant information on how morphological ...[more]

PMID: 31899763

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Project description:BACKGROUND:Steinernema carpocapsae is an entomopathogenic nematode that employs nictation and jumping behaviours to find potential insect hosts. Here we aimed to investigate the transcriptional basis of variant host-finding behaviours in the infective juvenile (IJ) stage of three S. carpocapsae strains (ALL, Breton and UK1), with a focus on neuronal genes known to influence behaviour in other nematode species. Identifying gene expression changes that correlate with variant host-finding behaviours will further our understanding of nematode biology. RESULTS:RNA-seq analysis revealed that whilst up to 28% of the S. carpocapsae transcriptome was differentially expressed (P < 0.0001) between strains, remarkably few of the most highly differentially expressed genes (> 2 log2 fold change, P < 0.0001) were from neuronal gene families. S. carpocapsae Breton displays increased chemotaxis toward the laboratory host Galleria mellonella, relative to the other strains. This correlates with the up-regulation of four srsx chemosensory GPCR genes, and a sodium transporter gene, asic-2, relative to both ALL and UK1 strains. The UK1 strain exhibits a decreased nictation phenotype relative to ALL and Breton strains, which correlates with co-ordinate up-regulation of neuropeptide like protein 36 (nlp-36), and down-regulation of an srt family GPCR gene, and a distinct asic-2-like sodium channel paralogue. To further investigate the link between transcriptional regulation and behavioural variation, we sequenced microRNAs across IJs of each strain. We have identified 283 high confidence microRNA genes, yielding 321 predicted mature microRNAs in S. carpocapsae, and find that up to 36% of microRNAs are differentially expressed (P < 0.0001) between strains. Many of the most highly differentially expressed microRNAs (> 2 log2 fold, P < 0.0001) are predicted to regulate a variety of neuronal genes that may contribute to variant host-finding behaviours. We have also found evidence for differential gene isoform usage between strains, which alters predicted microRNA interactions, and could contribute to the diversification of behaviour. CONCLUSIONS:These data provide insight to the transcriptional basis of behavioural variation in S. carpocapsae, supporting efforts to understand the molecular basis of complex behaviours in nematodes.

Project description:BackgroundSteinernema feltiae is an entomopathogenic nematode used in biological control programs with a global distribution. Populations of this species show phenotypic plasticity derived from local adaptation and vary in different traits, such as location and host penetration. The aim of this work was to describe a Chilean isolate of this nematode species, using integrative approaches.MethodsNematode morphological and morphometric studies were conducted along with molecular analysis of nuclear genes. The symbiotic bacterium was also identified by sequencing the 16S rRNA gene. Some ecological characteristics were described, including the temperature requirements for the nematode life cycle and the effect of soil water content for optimal reproduction.ResultsMorphometric characterization revealed a large intra-specific variability. The isolate identity was also corroborated with the analysis of nuclear genes. Based on the 16S gene, its symbiont bacteria, Xenorhabdus bovienii, was identified. The lowest, optimal and highest temperatures found to limit the infestation and reproduction on Galleria mellonella were 10, 20 and 30 °C, respectively; the emergence from the host larvae occurred approximately 10 days after inoculation. Differences were observed in offspring, and 120 infective juveniles (IJ)/larva was the most prolific dose at 20 °C. The soil water content did not affect the number of IJ invaders, penetration efficacy and IJ emergence time or offspring per larva, but it caused a delay in achieving full mortality at the permanent wilting point with respect to saturation and field capacity.ConclusionsFor the first time, a Chilean isolate of S. feltiae is described in detail considering morphological, molecular and ecological aspects. The isolate was shown to be efficient in soil containing water, with optimal temperatures ranging from 15 to 25 °C for host infestation and production of an abundant offspring; these characteristics would allow its potential use as control agents in a wide geographical area of the country.

Project description:Advances in sequencing technologies have accelerated our understanding of the complex genetic network of organisms and genomic divergences that are linked to evolutionary processes. While many model organisms and laboratory strains have been sequenced, wild populations are underrepresented in the growing list of sequenced genomes. Here, we present a de novo assembly of Steinernema feltiae, strain NW, collected from a working agricultural field in south central Washington, USA. Leveraging Pacific Biosciences (PacBio) long reads, we sequenced strain NW to a high depth (99×). The resulting de novo assembly is significantly larger than the previous assembly generated from the laboratory strain SN, with a noticeable improvement in continuity and completeness. Comparative analysis of two assemblies revealed numerous single nucleotide polymorphisms (SNPs), breakpoints, and indels present between the two genomes. This alternative genome resource and annotation could benefit the research community to examine the genetic foundation of evolutionary processes as well as genomic variation among conspecific populations.Advances in sequencing technologies have accelerated our understanding of the complex genetic network of organisms and genomic divergences that are linked to evolutionary processes. While many model organisms and laboratory strains have been sequenced, wild populations are underrepresented in the growing list of sequenced genomes. Here, we present a de novo assembly of Steinernema feltiae, strain NW, collected from a working agricultural field in south central Washington, USA. Leveraging Pacific Biosciences (PacBio) long reads, we sequenced strain NW to a high depth (99×). The resulting de novo assembly is significantly larger than the previous assembly generated from the laboratory strain SN, with a noticeable improvement in continuity and completeness. Comparative analysis of two assemblies revealed numerous single nucleotide polymorphisms (SNPs), breakpoints, and indels present between the two genomes. This alternative genome resource and annotation could benefit the research community to examine the genetic foundation of evolutionary processes as well as genomic variation among conspecific populations.

Dataset Information

Morphological adjustment in free-living Steinernema feltiae infective juveniles to increasing concentration of Nemafric-BL phytonematicide.

Publications

Morphological adjustment in free-living Steinernema feltiae infective juveniles to increasing concentration of Nemafric-BL phytonematicide.

Similar Datasets

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