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Abstract: Long‐term observations of ecological communities are necessary for generating and testing predictions of ecosystem responses to climate change. We investigated temporal trends and spatial patterns of soil fauna along similar environmental gradients in three sites of the McMurdo Dry Valleys, Antarctica, spanning two distinct climatic phases: a decadal cooling trend from the early 1990s through the austral summer of February 2001, followed by a shift to the current trend of warming summers and more frequent discrete warming events. After February 2001, we observed a decline in the dominant species (the nematode Scottnema lindsayae) and increased abundance and expanded distribution of less common taxa (rotifers, tardigrades, and other nematode species). Such diverging responses have resulted in slightly greater evenness and spatial homogeneity of taxa. However, total abundance of soil fauna appears to be declining, as positive trends of the less common species so far have not compensated for the declining numbers of the dominant species. Interannual variation in the proportion of juveniles in the dominant species was consistent across sites, whereas trends in abundance varied more. Structural equation modeling supports the hypothesis that the observed biological trends arose from dissimilar responses by dominant and less common species to pulses of water availability resulting from enhanced ice melt. No direct effects of mean summer temperature were found, but there is evidence of indirect effects via its weak but significant positive relationship with soil moisture. Our findings show that combining an understanding of species responses to environmental change with long‐term observations in the field can provide a context for validating and refining predictions of ecological trends in the abundance and diversity of soil fauna. [ABSTRACT FROM AUTHOR]

Gene silencing using RNAi is a powerful tool for functional analysis of nematode genes and can provide a new strategy for the management of root-knot nematodes. The transcript of the venom allergen-like protein gene ( Mhi-vap-1) of Meloidogyne hispanica is localized in the subventral oesophageal gland cells of second-stage juveniles (J2) and the gene is highly transcribed in this developmental nematode stage. The purpose of this study was to assess whether the silencing of the Mhi-vap-1 gene could affect nematode attraction to roots, penetration, development and reproduction in tomato plants. The optimum soaking time to generate silencing of this gene was determined by quantitative RT- PCR analysis of the relative expression of the Mhi-vap-1 gene in the J2 incubated with the soaking solution for 24, 32 and 48 h. At 48 h, the relative expression of Mhi-vap-1 decreased, which indicates that this period of time is optimum to silence this nematode gene using the RNAi method. Silencing of the Mhi-vap-1 gene interfered with the completion of the nematode life cycle and caused a reduction in nematode attraction to roots, penetration and infection of plants. A small difference in the number of females and galls formed was also observed, which caused a small decrease in the nematode reproduction factor. The use of RNAi silencing of the Meloidogyne effector gene Mhi-vap-1 showed that this gene is important for the plant-nematode interaction during the early events of infection and could be a target gene for anti-nematode strategies. [ABSTRACT FROM AUTHOR]

Parasitic nematodes have evolved sophisticated mechanisms to communicate with their hosts in order to survive and successfully establish an infection. The transfer of RNA within extracellular vesicles ( EVs) has recently been described as a mechanism that could contribute to this communication in filarial nematodes. It has been shown that these EVs are loaded with several types of RNAs, including micro RNAs, leading to the hypothesis that parasites could actively use these molecules to manipulate host gene expression and to the exciting prospect that these pathways could result in new diagnostic and therapeutic strategies. Here, we review the literature on the diverse RNAi pathways that operate in nematodes and more specifically our current knowledge of extracellular RNA (ex RNA) and EVs derived from filarial nematodes in vitro and within their hosts. We further detail some of the issues and questions related to the capacity of RNA-mediated communication to function in parasite-host interactions and the ability of ex RNA to enable us to distinguish and detect different nematode parasites in their hosts. [ABSTRACT FROM AUTHOR]

Climate change can promote disease emergence if shifting conditions favour infection of native fauna by introduced parasites and pathogens. In Hawai'i, climate warming is predicted to reduce net precipitation and surface flow in streams, which in turn could increase parasitism of native stream fishes by non-native parasites. In this study, we utilised a natural precipitation gradient across the Hamakua coast on the island of Hawai'i to assess the relationship between precipitation and infection of Awaous stamineus, a native amphidromous goby, by the introduced nematode Camallanus cotti. We found that the abundance, intensity and prevalence of C. cotti in A. stamineus increased with declining rainfall. Our results also show that parasitism tracks precipitation patterns across the archipelago and that parasitism increases even with moderate decreases in rainfall. As the Hamakua coast precipitation gradient represents a proxy for predicted climate-driven reductions in precipitation, these findings suggest that infection of native Hawaiian fishes by introduced parasites will increase if climate conditions change as expected. Our findings also suggest that parasitism may be exacerbated by other factors that reduce surface flow, including water extraction for agricultural and urban uses. If so, then adaptive management of minimum flow standards in Hawai'i and elsewhere could improve the well-being of at-risk native fishes by alleviating parasitism under current and future climate conditions. [ABSTRACT FROM AUTHOR]

Oxygen is fundamentally important for cell metabolism, and as a consequence, O2 deprivation (hypoxia) can impair many essential physiological processes. Here, we show that an active response to hypoxia disrupts cellular proteostasis – the coordination of protein synthesis, quality control, and degradation that maintains the functionality of the proteome. We have discovered that specific hypoxic conditions enhance the aggregation and toxicity of aggregation-prone proteins that are associated with neurodegenerative diseases. Our data indicate this is an active response to hypoxia, rather than a passive consequence of energy limitation. This response to hypoxia is partially antagonized by the conserved hypoxia-inducible transcription factor, hif-1. We further demonstrate that exposure to hydrogen sulfide (H2S) protects animals from hypoxia-induced disruption of proteostasis. H2S has been shown to protect against hypoxic damage in mammals and extends lifespan in nematodes. Remarkably, our data also show that H2S can reverse detrimental effects of hypoxia on proteostasis. Our data indicate that the protective effects of H2S in hypoxia are mechanistically distinct from the effect of H2S to increase lifespan and thermotolerance, suggesting that control of proteostasis and aging can be dissociated. Together, our studies reveal a novel effect of the hypoxia response in animals and provide a foundation to understand how the integrated proteostasis network is integrated with this stress response pathway. [ABSTRACT FROM AUTHOR]

C aenorhabditis elegans, originally isolated from soil, is a nematode used in various fields of biological research including host-microbe interaction. While bacterial pathogens responsible for human infections have been actively studied in C . elegans, very few bacterial species that provide beneficial effects on C . elegans have been reported. Here, we tested several bacterial soil isolates and then characterized the effects of L ysinibacillus sphaericus on C . elegans growth-related phenotypes. Worms fed with L . sphaericus lived significantly longer than those growing with typical E scherichia coli OP50. Early- and juvenile-stage growth was also highly stimulated by L . sphaericus; body size at 28 h post-hatching was > 2 times larger than OP50-fed worms and L . sphaericus-fed worms moved through the larval stage development more rapidly than control worms. In addition, significantly elevated fertilization was observed in worms fed with L . sphaericus (∼ 8 h faster than the control group). Furthermore, growth with L . sphaericus resulted in the production of larger numbers of progeny than the control growth with OP50. Worms grown with L . sphaericus were highly resistant to oxidative, osmotic and infection stresses. Together, our results reveal a novel mode of growth that involves healthy ageing of nematodes. [ABSTRACT FROM AUTHOR]

Pseudomonas fluorescens, strains L124, L228, L321, and the positive control strain F113 used in this study, produce compounds associated with plant growth promotion, biocontrol, antimicrobial and antiviral activity, and adaptation to stresses. These bacterial strains were tested in vitro and in vivo in tomato plants, to determine their potential role in Meloidogyne javanica suppression. In laboratory experiments, only 2% of M. javanica eggs hatched when exposed to the metabolites of each bacterial strain. Additionally, 100% M. javanica J2 mortality was recorded when nematodes were exposed to the metabolites of F113 and L228. In greenhouse experiments, M. javanica infected tomato plants, which were also inoculated with the bacterial strains F113 and L124, displayed the highest biomass (height, number of leaves, fresh and dry weight) of all bacterial treatments tested. Results from the development and induced systemic resistance experiments indicated that the bacterial strains F113 and L321 had the most effective biocontrol capacity over nematode infection, delayed nematode development (J3/J4, adults and galls), and reduced nematode fecundity. In addition, these results indicated that the bacterial strain L124 is an effective plant growth promoter of tomato plants. Furthermore, it was determined that the bacterial strain L321 was capable of M. javanica biocontrol. P. fluorescens F113 was effective at both increasing tomato plant biomass and M. javanica biocontrol. In an agricultural context, applying successional drenches with these beneficial plant growth promoting rhizobacteria would ensure bacteria viability in the rhizosphere of the plants, encourage positive plant bacterial interactions and increase biocontrol against M. javanica., (© 2022 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.)

SUMMARY Determining the causes and evolution of reproductive barriers to gene flow between populations, speciation, is the key to understanding the origin of diversity in nature. Many species manifest hybrid breakdown when they intercross, characterized by increasingly exacerbated problems in later generations of hybrids. Recently, Caenorhabditis nematodes have emerged as a genetic model for studying speciation, and here we investigate the nature and causes of hybrid breakdown between Caenorhabditis remanei and C. latens. We quantify partial F1 hybrid inviability and extensive F2 hybrid inviability; the ∼75% F2 embryonic arrest occurs primarily during gastrulation or embryonic elongation. Moreover, F1 hybrid males exhibit Haldane's rule asymmetrically for both sterility and inviability, being strongest when C. remanei serves as maternal parent. We show that the mechanism by which sterile hybrid males are incapable of transferring sperm or a copulatory plug involves defective gonad morphogenesis, which we hypothesize results from linker cell defects in migration and/or cell death during development. This first documented case of partial hybrid male sterility in Caenorhabditis follows expectations of Darwin's corollary to Haldane's rule for asymmetric male fitness, providing a powerful foundation for molecular dissection of intrinsic reproductive barriers and divergence of genetic pathways controlling organ morphogenesis. [ABSTRACT FROM AUTHOR]

Summary The bacterium, Photorhabdus luminescens, is an insect pathogen that also maintains a mutualistic interaction with nematodes from the family Heterorhabditis. Photorhabdus luminescens is carried in the gut of the infective juvenile (IJ), a nematode stage that infects soft-cuticled insect larvae in the soil. Photorhabdus luminescens is released into the insect blood to convert the insect into a biomass that is able to support nematode growth and development. Nematode reproduction continues for 2-3 generations before the nematodes enter an alternative developmental pathway leading to a new generation of IJs that are efficiently colonized by P. luminescens in a process called transmission. Transmission begins with the adherence of P. luminescens to the rectal gland cells (RGC) located in the gut of the hermaphrodite. The bacteria enter, and replicate within, the RGC resulting in vacuolization, and ultimately lysis, of the RGC. In this way P. luminescens are released throughout the body cavity of the hermaphrodite to encounter, and colonize, the developing IJs. In this study we show that the LysR-type regulator, HdfR, is required for normal transmission in P. luminescens TTO1. Transcriptome analysis revealed that HdfR regulates the expression of 124 genes, including genes involved in arginine metabolism, hydroxyphenylacetate catabolism and pigment production. Using fluorescence microscopy we show that the ΔhdfR mutant is able to attach to, and grow within, the hermaphrodite as well as wild-type bacteria but subsequent steps in transmission are delayed. Therefore, HdfR plays an important role in coordinating the interaction between P. luminescens and its nematode partner during transmission. [ABSTRACT FROM AUTHOR]

The article presents a review of research studies on developmental biology and genetics of Caenorhabditis elegans. These studies cover various aspects of the nematode including its embryonic cell lineage, cellular interactions in early Caenorhabditis elegans embryos, and the series of binary decisions that take place in the embryo. The problem with the transmission of valuable knowledge attrition in these studies is mentioned.