A Critical Appraisal of DNA Transfer from Plants to Parasitic Cyst Nematodes.

Plant-parasitic nematodes are one of the most economically important pests of crops. It is widely accepted that horizontal gene transfer-the natural acquisition of foreign genes in parasitic nematodes-contributes to parasitism. However, an apparent paradox has emerged from horizontal gene transfer analyses: On the one hand, distantly related organisms with very dissimilar genetic structures (i.e. bacteria), and only transient interactions with nematodes as far as we know, dominate the list of putative donors, while on the other hand, considerably more closely related organisms (i.e. the host plant), with similar genetic structure (i.e. introns) and documented long-term associations with nematodes, are rare among the list of putative donors. Given that these nematodes ingest cytoplasm from a living plant cell for several weeks, there seems to be a conspicuous absence of plant-derived cases. Here, we used comparative genomic approaches to evaluate possible plant-derived horizontal gene transfer events in plant parasitic nematodes. Our evidence supports a cautionary message for plant-derived horizontal gene transfer cases in the sugar beet cyst nematode, Heterodera schachtii. We propose a 4-step model for horizontal gene transfer from plant to parasite in order to evaluate why the absence of plant-derived horizontal gene transfer cases is observed. We find that the plant genome is mobilized by the nematode during infection, but that uptake of the said "mobilome" is the first major barrier to horizontal gene transfer from host to nematode. These results provide new insight into our understanding of the prevalence/role of nucleic acid exchange in the arms race between plants and plant parasites.

Rewiring the Sex-Determination Pathway During the Evolution of Self-Fertility.

Although evolution is driven by changes in how regulatory pathways control development, we know little about the molecular details underlying these transitions. The TRA-2 domain that mediates contact with TRA-1 is conserved in Caenorhabditis. By comparing the interaction of these proteins in two species, we identified a striking change in how sexual development is controlled. Identical mutations in this domain promote oogenesis in Caenorhabditis elegans but promote spermatogenesis in Caenorhabditis briggsae. Furthermore, the effects of these mutations involve the male-promoting gene fem-3 in C. elegans but are independent of fem-3 in C. briggsae. Finally, reciprocal mutations in these genes show that C. briggsae TRA-2 binds TRA-1 to prevent expression of spermatogenesis regulators. By contrast, in C. elegans TRA-1 sequesters TRA-2 in the germ line, allowing FEM-3 to initiate spermatogenesis. Thus, we propose that the flow of information within the sex determination pathway has switched directions during evolution. This result has important implications for how evolutionary change can occur.

Without mechanisms, theories and models in insect epigenetics remain a black box.

Insect epigenetics must confront the remarkable diversity of epigenomic systems in various lineages and use mechanistic approaches to move beyond vague functional explanations based on predictions and inferences. To accelerate progress, what is required now is a convergence of genomic data with biochemical and single-cell-type analyses in selected species representing contrasting evolutionary solutions in epigenetics.

The Endocannabinoid System in Caenorhabditis elegans.

The existence of a formal Endocannabinoid System in C. elegans has been questioned due to data showing the absence of typical cannabinoid receptors in the worm; however, the presence of a full metabolism for endocannabinoids, alternative ligands, and receptors for these agents and a considerable number of orthologous and homologous genes regulating physiological cannabinoid-like signals and responses - several of which are similar to those of mammals - demonstrates a well-structured and functional complex system in nematodes. In this review, we describe and compare similarities and differences between the Endocannabinoid System in mammals and nematodes, highlighting the basis for the integral study of this novel system in the worm.

Unveiling the Diversity: Plant Parasitic Nematode Effectors and Their Plant Interaction Partners.

Root-knot and cyst nematodes are two groups of plant parasitic nematodes that cause the majority of crop losses in agriculture. As a result, these nematodes are the focus of most nematode effector research. Root-knot and cyst nematode effectors are defined as secreted molecules, typically proteins, with crucial roles in nematode parasitism. There are likely hundreds of secreted effector molecules exuded through the nematode stylet into the plant. The current research has shown that nematode effectors can target a variety of host proteins and have impacts that include the suppression of plant immune responses and the manipulation of host hormone signaling. The discovery of effectors that localize to the nucleus indicates that the nematodes can directly modulate host gene expression for cellular reprogramming during feeding site formation. In addition, plant peptide mimicry by some nematode effectors highlights the sophisticated strategies the nematodes employ to manipulate host processes. Here we describe research on the interactions between nematode effectors and host proteins that will provide insights into the molecular mechanisms underpinning plant-nematode interactions. By identifying the host proteins and pathways that are targeted by root-knot and cyst nematode effectors, scientists can gain a better understanding of how nematodes establish feeding sites and subvert plant immune responses. Such information will be invaluable for future engineering of nematode-resistant crops, ultimately fostering advancements in agricultural practices and crop protection. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 "No Rights Reserved" license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2024.

Diversity and evolution of transposable elements in the plant-parasitic nematodes.

BACKGROUND: Transposable elements (TEs) are mobile DNA sequences that propagate within genomes, occupying a significant portion of eukaryotic genomes and serving as a source of genetic variation and innovation. TEs can impact genome dynamics through their repetitive nature and mobility. Nematodes are incredibly versatile organisms, capable of thriving in a wide range of environments. The plant-parasitic nematodes are able to infect nearly all vascular plants, leading to significant crop losses and management expenses worldwide. It is worth noting that plant parasitism has evolved independently at least three times within this nematode group. Furthermore, the genome size of plant-parasitic nematodes can vary substantially, spanning from 41.5 Mbp to 235 Mbp. To investigate genome size variation and evolution in plant-parasitic nematodes, TE composition, diversity, and evolution were analysed in 26 plant-parasitic nematodes from 9 distinct genera in Clade IV. RESULTS: Interestingly, despite certain species lacking specific types of DNA transposons or retrotransposon superfamilies, they still exhibit a diverse range of TE content. Identification of species-specific TE repertoire in nematode genomes provides a deeper understanding of genome evolution in plant-parasitic nematodes. An intriguing observation is that plant-parasitic nematodes possess extensive DNA transposons and retrotransposon insertions, including recent sightings of LTR/Gypsy and LTR/Pao superfamilies. Among them, the Gypsy superfamilies were found to encode Aspartic proteases in the plant-parasitic nematodes. CONCLUSIONS: The study of the transposable element (TE) composition in plant-parasitic nematodes has yielded insightful discoveries. The findings revealed that certain species exhibit lineage-specific variations in their TE makeup. Discovering the species-specific TE repertoire in nematode genomes is a crucial element in understanding the evolution of genomes in plant-parasitic nematodes. It allows us to gain a deeper insight into the intricate workings of these organisms and their genetic makeup. With this knowledge, we are gaining a fundamental piece in the puzzle of understanding the evolution of these parasites. Moreover, recent transpositions have led to the acquisition of new TE superfamilies, especially Gypsy and Pao retrotransposons, further expanding the diversity of TEs in these nematodes. Significantly, the widely distributed Gypsy superfamily possesses proteases that are exclusively associated with parasitism during nematode-host interactions. These discoveries provide a deeper understanding of the TE landscape within plant-parasitic nematodes.

Wuchereria bancrofti Lymphatic Filariasis, Barrancabermeja, Colombia, 2023.

We describe a recent case of lymphatic filariasis in Colombia caused by Wuchereria bancrofti nematodes. Our study combines clinical-epidemiologic findings with phylogenetic data. Resurgence of lymphatic filariasis may be linked to increasing urbanization trends and migration from previously endemic regions. Fieldwork can be a beneficial tool for screening and containing transmission.

Zoonotic Ancylostoma ceylanicum Infection in Coyotes from Guanacaste Conservation Area, Costa Rica, 2021.

Ancylostoma ceylanicum is the second most common hookworm infecting humans in the Asia-Pacific region. Recent reports suggest presence of the parasite in the Americas. We report A. ceylanicum infections in coyotes from the Guanacaste Conservation Area, Costa Rica. Our findings call for active surveillance in humans and animals.

Ocular Dirofilariasis in Migrant from Sri Lanka, Australia.

We describe a case of imported ocular dirofilariasis in Australia, linked to the Hong Kong genotype of Dirofilaria sp., in a migrant from Sri Lanka. Surgical extraction and mitochondrial sequences analyses confirmed this filarioid nematode as the causative agent and a Dirofilaria sp. not previously reported in Australia.

VND genes redundantly regulate cell wall thickening during parasitic nematode infection.

Plant-parasitic root knot nematodes are major agricultural pests worldwide, as they infect plant roots and cause substantial damages to crop plants. Root-knot nematodes induce specialized feeding cells known as giant cells in the root vasculature, which serve as nutrient reservoirs for the infecting nematodes. Here we show that the cell walls of giant cells thicken to form pitted patterns that superficially resemble to metaxylem cells. Interestingly, VASCULAR-RELATED NAC-DOMAIN1 (VND1) was found to be up-regulated, while the xylem-type programmed cell death marker XYLEM CYSTEINE PEPTIDASE 1 (XCP1) was down-regulated upon nematode infection. The vnd2 and vnd3 mutants showed reduced secondary cell wall pore size, while the vnd1 vnd2 vnd3 triple mutant produced significantly fewer nematode egg masses when compared with the wild type. These results suggest that giant cell development pathway likely share common signaling modules with the metaxylem differentiation pathway, and VND1, VND2, and VND3 redundantly regulate plant-nematode interaction through secondary cell wall formation.

Green iron oxide nanoparticles and magnetic nanobiochar: enhancing tomato performance, phytochemicals, and root-knot nematode resistance.

BACKGROUND: Green nanoparticles are considered to be an effective strategy for improving phytochemicals and raising productivity in soil infected by root-knot nematodes. This work aims to understand the characteristics of certain nanomaterials, including non-iron (nFe), green non-iron (GnFe), and green magnetic nanobiochar (GMnB), and the effect of adding them at 3 and 6 mg kg- 1 on phytochemicals and tomato (Solanum lycopersicum) plant growth in soils infected by root-knot nematodes. RESULTS: Spectroscopic characterization of nanomaterials showed that nFe, GnFe, and GMnB contained functional groups (e.g., Fe-O, S-H, C-H, OH, and C = C) and possessed a large surface area. Application of GMB at 6 mg kg- 1 was the most efficient treatment for increasing the phytochemicals of the tomato plant, with a rise of 123.2% in total phenolic, 194.7% in total flavonoids, 89.7% in total carbohydrate, 185.2% in total free amino acids, and 165.1% in total tannin compared to the untreated soil. Tomato plant growth and attributes increased with increasing levels of soil nano-amendment in this investigation. The addition of GnFe3 and GnFe6 increased the reduction of root galls of root-knot nematodes by 22.44% and 17.76% compared with nFe3 and nFe6, respectively. The inclusion of the examined soil nano-amendments increased phytochemicals and reduced the total number of root-knot nematodes on tomato plants at varying rates, which played a significant role in enhancing tomato growth. CONCLUSIONS: In conclusion, treating tomato plants with GnFe or GMnB can be used as a promising green nanomaterial to eliminate root-knot nematodes and increase tomato yield in sandy clay loam soil.

Newly identified nematodes from the Great Salt Lake are associated with microbialites and specially adapted to hypersaline conditions.

Extreme environments enable the study of simplified food-webs and serve as models for evolutionary bottlenecks and early Earth ecology. We investigated the biodiversity of invertebrate meiofauna in the benthic zone of the Great Salt Lake (GSL), Utah, USA, one of the most hypersaline lake systems in the world. The hypersaline bays within the GSL are currently thought to support only two multicellular animals: brine fly larvae and brine shrimp. Here, we report the presence, habitat, and microbial interactions of novel free-living nematodes. Nematode diversity drops dramatically along a salinity gradient from a freshwater river into the south arm of the lake. In Gilbert Bay, nematodes primarily inhabit reef-like organosedimentary structures built by bacteria called microbialites. These structures likely provide a protective barrier to UV and aridity, and bacterial associations within them may support life in hypersaline environments. Notably, sampling from Owens Lake, another terminal lake in the Great Basin that lacks microbialites, did not recover nematodes from similar salinities. Phylogenetic divergence suggests that GSL nematodes represent previously undescribed members of the family Monhysteridae-one of the dominant fauna of the abyssal zone and deep-sea hydrothermal vents. These findings update our understanding of halophile ecosystems and the habitable limit of animals.

No correlative evidence of costs of infection or immunity on leucocyte telomere length in a wild population of Soay sheep.

Telomere length (TL) is a biomarker hypothesized to capture evolutionarily and ecologically important physiological costs of reproduction, infection and immunity. Few studies have estimated the relationships among infection status, immunity, TL and fitness in natural systems. The hypothesis that short telomeres predict reduced survival because they reflect costly consequences of infection and immune investment remains largely untested. Using longitudinal data from a free-living Soay sheep population, we tested whether leucocyte TL was predicted by infection with nematode parasites and antibody levels against those parasites. Helminth parasite burdens were positively associated with leucocyte TL in both lambs and adults, which is not consistent with TL reflecting infection costs. We found no association between TL and helminth-specific IgG levels in either young or old individuals which suggests TL does not reflect costs of an activated immune response or immunosenescence. Furthermore, we found no support for TL acting as a mediator of trade-offs between infection, immunity and subsequent survival in the wild. Our results suggest that while variation in TL could reflect short-term variation in resource investment or environmental conditions, it does not capture costs of infection and immunity, nor does it behave like a marker of an individual's helminth-specific antibody immune response.

Unraveling the enigma of root-knot nematodes: from origins to advanced management strategies in agriculture.

MAIN CONCLUSION: Integrated management strategies, including novel nematicides and resilient cultivars, offer sustainable solutions to combat root-knot nematodes, crucial for safeguarding global agriculture against persistent threats. Root-knot nematodes (RKN) pose a significant threat to a diverse range of host plants, with their obligatory endoparasitic nature leading to substantial agricultural losses. RKN spend much of their lives inside or in contact by secreting plant cell wall-modifying enzymes resulting in the giant cell development for establishing host-parasite relationships. Additionally, inflicting physical harm to host plants, RKN also contributes to disease complexes creation with fungi and bacteria. This review comprehensively explores the origin, history, distribution, and physiological races of RKN, emphasizing their economic impact on plants through gall formation. Management strategies, ranging from cultural and physical to biological and chemical controls, along with resistance mechanisms and marker-assisted selection, are explored. While recognizing the limitations of traditional nematicides, recent breakthroughs in non-fumigant alternatives like fluensulfone, spirotetramat, and fluopyram offer promising avenues for sustainable RKN management. Despite the success of resistance mechanisms like the Mi gene, challenges persist, prompting the need for integrative approaches to tackle Mi-virulent isolates. In conclusion, the review stresses the importance of innovative and resilient control measures for sustainable agriculture, emphasizing ongoing research to address evolving challenges posed by RKN. The integration of botanicals, resistant cultivars, and biological controls, alongside advancements in non-fumigant nematicides, contributes novel insights to the field, laying the ground work for future research directions to ensure the long-term sustainability of agriculture in the face of persistent RKN threats.

The other side of the coin: systemic effects of Serendipita indica root colonization on development of sedentary plant-parasitic nematodes in Arabidopsis thaliana.

MAIN CONCLUSION: Upon systemic S. indica colonization in split-root system cyst and root-knot nematodes benefit from endophyte-triggered carbon allocation and altered defense responses what significantly facilitates their development in A. thaliana. Serendipita indica is an endophytic fungus that establishes mutualistic relationships with different plants including Arabidopsis thaliana. It enhances host's growth and resistance to different abiotic and biotic stresses such as infestation by the cyst nematode Heterodera schachtii (CN). In this work, we show that S. indica also triggers similar direct reduction in development of the root-knot nematode Meloidogyne javanica (RKN) in A. thaliana. Further, to mimick the natural situation occurring frequently in soil where roots are unequally colonized by endophytes we used an in vitro split-root system with one half of A. thaliana root inoculated with S. indica and the other half infected with CN or RKN, respectively. Interestingly, in contrast to direct effects, systemic effects led to an increase in number of both nematodes. To elucidate this phenomenon, we focused on sugar metabolism and defense responses in systemic non-colonized roots of plants colonized by S. indica. We analyzed the expression of several SUSs and INVs as well as defense-related genes and measured sugar pools. The results show a significant downregulation of PDF1.2 as well as slightly increased sucrose levels in the non-colonized half of the root in three-chamber dish. Thus, we speculate that, in contrast to direct effects, both nematode species benefit from endophyte-triggered carbon allocation and altered defense responses in the systemic part of the root, which promotes their development. With this work, we highlight the complexity of this multilayered tripartite relationship and deliver new insights into sugar metabolism and plant defense responses during S. indica-nematode-plant interaction.

Biochemical and nanotechnological approaches to combat phytoparasitic nematodes.

The foundation of most food production systems underpinning global food security is the careful management of soil resources. Embedded in the concept of soil health is the impact of diverse soil-borne pests and pathogens, and phytoparasitic nematodes represent a particular challenge. Root-knot nematodes and cyst nematodes are severe threats to agriculture, accounting for annual yield losses of US$157 billion. The control of soil-borne phytoparasitic nematodes conventionally relies on the use of chemical nematicides, which can have adverse effects on the environment and human health due to their persistence in soil, plants, and water. Nematode-resistant plants offer a promising alternative, but genetic resistance is species-dependent, limited to a few crops, and breeding and deploying resistant cultivars often takes years. Novel approaches for the control of phytoparasitic nematodes are therefore required, those that specifically target these parasites in the ground whilst minimizing the impact on the environment, agricultural ecosystems, and human health. In addition to the development of next-generation, environmentally safer nematicides, promising biochemical strategies include the combination of RNA interference (RNAi) with nanomaterials that ensure the targeted delivery and controlled release of double-stranded RNA. Genome sequencing has identified more than 75 genes in root knot and cyst nematodes that have been targeted with RNAi so far. But despite encouraging results, the delivery of dsRNA to nematodes in the soil remains inefficient. In this review article, we describe the state-of-the-art RNAi approaches targeting phytoparasitic nematodes and consider the potential benefits of nanotechnology to improve dsRNA delivery.

The Xenorhabdus nematophila LrhA transcriptional regulator modulates production of γ-keto-N-acyl amides with inhibitory activity against mutualistic host nematode egg hatching.

Xenorhabdus nematophila is a symbiotic Gammaproteobacterium that produces diverse natural products that facilitate mutualistic and pathogenic interactions in their nematode and insect hosts, respectively. The interplay between X. nematophila secondary metabolism and symbiosis stage is tuned by various global regulators. An example of such a regulator is the LysR-type protein transcription factor LrhA, which regulates amino acid metabolism and is necessary for virulence in insects and normal nematode progeny production. Here, we utilized comparative metabolomics and molecular networking to identify small molecule factors regulated by LrhA and characterized a rare γ-ketoacid (GKA) and two new N-acyl amides, GKA-Arg (1) and GKA-Pro (2) which harbor a γ-keto acyl appendage. A lrhA null mutant produced elevated levels of compound 1 and reduced levels of compound 2 relative to wild type. N-acyl amides 1 and 2 were shown to be selective agonists for the human G-protein-coupled receptors (GPCRs) C3AR1 and CHRM2, respectively. The CHRM2 agonist 2 deleteriously affected the hatch rate and length of Steinernema nematodes. This work further highlights the utility of exploiting regulators of host-bacteria interactions for the identification of the bioactive small molecule signals that they control. IMPORTANCE: Xenorhabdus bacteria are of interest due to their symbiotic relationship with Steinernema nematodes and their ability to produce a variety of natural bioactive compounds. Despite their importance, the regulatory hierarchy connecting specific natural products and their regulators is poorly understood. In this study, comparative metabolomic profiling was utilized to identify the secondary metabolites modulated by the X. nematophila global regulator LrhA. This analysis led to the discovery of three metabolites, including an N-acyl amide that inhibited the egg hatching rate and length of Steinernema carpocapsae nematodes. These findings support the notion that X. nematophila LrhA influences the symbiosis between X. nematophila and S. carpocapsae through N-acyl amide signaling. A deeper understanding of the regulatory hierarchy of these natural products could contribute to a better comprehension of the symbiotic relationship between X. nematophila and S. carpocapsae.

Effects of the nematode Litylenchus crenatae subsp. mccannii and beech leaf disease on leaf fungal and bacterial communities on Fagus grandifolia (American beech).

Beech leaf disease (BLD) is a newly emerging disease in North America that affects American beech (Fagus grandifolia). It is increasingly recognized that BLD is caused by a subspecies of the anguinid nematode Litylenchus crenatae subsp. mccannii (hereafter L. crenatae), which is likely native to East Asia. How nematode infestation of leaves affects the leaf microbiome and whether changes in the microbiome could contribute to BLD symptoms remain uncertain. In this study, we examined bacterial and fungal communities associated with the leaves of F. grandifolia across nine sites in Ohio and Pennsylvania that were either symptomatic or asymptomatic for BLD and used qPCR to measure relative nematode infestation levels. We found significantly higher levels of infestation at sites visibly symptomatic for BLD. Low levels of nematode infestation were also observed at asymptomatic sites, which suggests that nematodes can be present without visible symptoms evident. Bacterial and fungal communities were significantly affected by sampling site and symptomology, but only fungal communities were affected by nematode presence alone. We found many significant indicators of both bacteria and fungi related to symptoms of BLD, with taxa generally occurring in both asymptomatic and symptomatic leaves, suggesting that microbes are not responsible for BLD but could act as opportunistic pathogens. Of particular interest was the fungal genus Erysiphe, which is common in the Fagaceae and is reported to overwinter in buds-a strategy consistent with L. crenatae. The specific role microbes play in opportunistic infection of leaves affected by L. crenatae will require additional study. IMPORTANCE: Beech leaf disease (BLD) is an emerging threat to American beech (Fagus grandifolia) and has spread quickly throughout the northeastern United States and into southern Canada. This disease leads to disfigurement of leaves and is marked by characteristic dark, interveinal banding, followed by leaf curling and drop in more advanced stages. BLD tends to especially affect understory leaves, which can lead to substantial thinning of the forest understory where F. grandifolia is a dominant tree species. Understanding the cause of BLD is necessary to employ management strategies that protect F. grandifolia and the forests where it is a foundation tree species. Current research has confirmed that the foliar nematode Litylenchus crenatae subsp. mccannii is required for BLD, but whether other organisms are involved is currently unknown. Here, we present a study that investigated leaf-associated fungi and bacteria of F. grandifolia to understand more about how microorganisms may contribute to BLD.

The regeneration conferring transcription factor complex ERF115-PAT1 coordinates a wound-induced response in root-knot nematode induced galls.

The establishment of root-knot nematode (RKN; Meloidogyne spp.) induced galls in the plant host roots likely involves a wound-induced regeneration response. Confocal imaging demonstrates physical stress or injury caused by RKN infection during parasitism in the model host Arabidopsis thaliana. The ERF115-PAT1 heterodimeric transcription factor complex plays a recognized role in wound-induced regeneration. ERF115 and PAT1 expression flanks injured gall cells likely driving mechanisms of wound healing, implying a local reactivation of cell division which is also hypothetically involved in gall genesis. Herein, functional investigation revealed that ectopic ERF115 expression resulted in premature induction of galls, and callus formation adjacent to the expanding female RKN was seen upon PAT1 upregulation. Smaller galls and less reproduction were observed in ERF115 and PAT1 knockouts. Investigation of components in the ERF115 network upon overexpression and knockdown by qRT-PCR suggests it contributes to steer gall wound-sensing and subsequent competence for tissue regeneration. High expression of CYCD6;1 was detected in galls, and WIND1 overexpression resulted in similar ERF115OE gall phenotypes, also showing faster gall induction. Along these lines, we show that the ERF115-PAT1 complex likely coordinates stress signalling with tissue healing, keeping the gall functional until maturation and nematode reproduction.

Redox signalling in plant-nematode interactions: Insights into molecular crosstalk and defense mechanisms.

Plant-parasitic nematodes, specifically cyst nematodes (CNs) and root-knot nematodes (RKNs), pose significant threats to global agriculture, leading to substantial crop losses. Both CNs and RKNs induce permanent feeding sites in the root of their host plants, which then serve as their only source of nutrients throughout their lifecycle. Plants deploy reactive oxygen species (ROS) as a primary defense mechanism against nematode invasion. Notably, both CNs and RKNs have evolved sophisticated strategies to manipulate the host's redox environment to their advantage, with each employing distinct tactics to combat ROS. In this review, we have focused on the role of ROS and its scavenging network in interactions between host plants and CNs and RKNs. Overall, this review emphasizes the complex interplay between plant defense mechanism, redox signalling and nematode survival tactics, suggesting potential avenues for developing innovative nematode management strategies in agriculture.