Symbiosis最新文献

The agave weevil, Scyphophorus acupunctatus, is a pest of agave. Its larvae cause damage to agaves by boring holes in the plant. Boring requires that the insect consume the constituents of its host plant, which contains sugars and many recalcitrant polymers. It has been hypothesized for many years that the gut bacterial communities of S. acupunctatus play a role in its ability to metabolize agave components. However, studies exploring this insect's gut bacterial communities have yet to be performed. In this work, we used a 16S rRNA gene-based metabarcoding approach to characterize the gut bacterial communities of field-collected agave weevils from different localities in Mexico. We found that external factors, including host plants, have important effects on the structure of the gut bacterial communities of S. acupunctatus. Despite this variability, we found a discrete core bacterial community mainly composed of the genera Prevotella, Pectinatus, Liquorilactobacillus, Secundilactobacillus, Paucilactobacillus, and Pseudomonas. These genera may be necessary for S. acupunctatus as metabolic helpers and/or gatekeepers. Additional studies are needed to fully assess the functionality of the gut bacterial community of this species in terms of its metabolic contribution, which may help to decipher their potential ecological implications. The information we provided here is the first step for guiding further questions.

Cycads are the only gymnosperms forming a symbiosis with nitrogen-fixing cyanobacteria in a specialized organ: the coralloid root. This paper investigates the endophytic bacterial community inhabiting the coralloid roots of two cycads from Panama. We sampled coralloid roots from Zamia nana (terrestrial) and Zamia pseudoparasitica (epiphytic). Then, we used the 16S rRNA amplicon marker to describe the entire bacterial community. We also designed a new marker to amplify the rbcL-rbcX spacer and around 100 bp of the rbcX gene, targeting cyanobacteria. We found that using 16S, endophytic bacteria diversity is represented mainly by the phyla Actinobacteria, Cyanobacteria, and Proteobacteria. In addition, 16S analyses showed that Zamia species do not share a core cyanobacterial community (using stringent 75% and 90% thresholds), while the two species shared 4 ASVs at a 50% threshold. The newly developed rbcL-rbcX marker revealed that both species share a core cyanobacterial community represented by a single amplicon sequence variant (ASV1) (Nostoc sp.) at 90% threshold that is found in the same phylogenetic clade of that contain mostly Panamanian symbiotic cyanobacteria. Using a 75% threshold, only three ASVs (ASV1, ASV2, ASV3) were present across samples, and five ASVs at 50% threshold. This new marker can effectively identify cyanobacteria ASVs and provide a better resolution for microbial analyses in autotroph cyanobacterial symbioses.

Phoresy is likely a commensal interaction, in which a phoront attaches itself to the body of a host for dispersal. Host traits and environmental characteristics may determine phoresy patterns. We examined whether the density of microscopic phoronts on frogs living in the water between the leaves of bromeliads (phytotelma) was determined by the species, richness, size and abundance of anurans (frog hosts). We identified phoronts on the skin of three hylid species (Dendropsophus bromeliaceus, Phyllodytes luteolus, and Ololygon arduoa) associated to bromeliads at eight sites in the Atlantic Forest of Brazil. We report the first records of phoretic interaction between these bromeligenous frog hosts with the aquatic invertebrates of bromeliads e.g., Bdelloidea, Copepoda, Acari, and Ostracoda. The size of frog hosts had negative relationship with the abundance of phoronts. However, when the species were analyzed separately, the size of O. arduoa had positive relationship with the abundance of phoronts. The richness of anurans in bromeliads did not influence phoresy in any of the observed variables. Our results showed that host attributes, such as identity, size, and abundance, as well as the density of phoronts in their habitat, influenced the phoresy rates. This implies that not only host attributes, but also those of the phoront need to be considered in phoresy studies.

Soil microbes are influenced by their environment, and soil pH is well known as a driver of community structure, including within the plant root zone. However, the effect of pH induced changes on root-associated microbial communities for plant growth, resource allocation, and disease resistance is not well understood, especially for long-lived woody plants. In this study, we examined whether soil microbial communities altered by soil pH could affect tree growth, resource allocation, and resistance to a soil-borne pathogen. In a controlled greenhouse setting, we treated Fagus grandifolia saplings with small amounts of forest soil that had been manipulated to alter soil pH and microbial communities. In addition, 1-yr after inoculation with forest soil, half of the trees were also inoculated with the root rot pathogen Phytophthora cinnamomi to induce physiological stress. Tree growth showed no response to treatment with forest microbes; however, P. cinnamomi altered resource allocation, leading to increased ratios of aboveground to belowground biomass for trees treated with forest microbes. Interestingly, trees grown in pasteurized soil had a tendency toward the opposite pattern of reduced ratios of aboveground to belowground biomass. Soil treatment and pathogen inoculation interacted to alter water transport tissues; stems grown with microbes from acidic forest soil had higher vessel density when challenged with P. cinnamomi, while trees grown with microbes from neutral forest soil had higher vessel density in the absence of the pathogen. Our study suggests that the composition of root-associated microbes can affect resource allocation under stressful conditions for long-lived woody plants.

The orchid family (Orchidaceae) is one of the most diverse plant families in the world, but at the same time also contains one of the largest number of rare and endangered species. While conservation actions such as in situ and ex situ conservation and prohibition of international trade of wild orchids have achieved positive results to slow down the current decline of orchids, species with high medicinal or ornamental value may require more advanced measures. Recent pilot studies using novel cultivation techniques have successfully reintroduced endangered epiphytic orchids and facilitated the commercial cultivation of medicinal orchids. Because fungal partners play a key role in in situ symbiotic seed germination and industrial cultivation, we advocate for the development of fungus banks in laboratories engaging in orchid research, where fungi obtained from germinating seeds or seedlings can be studied and used to improve orchid germination under both in vitro and in situ conditions. Furthermore, these fungi could be shared nationally and internationally, enhancing orchid conservation efforts across the globe. Similar to seed banks, the development of fungus banks will reduce the possibility of fungi going extinct and ensure their availability for reintroduction programs and commercial cultivation. With the availability of both a fungus and seed bank, the conservation of threatened orchid species can be significantly enhanced by improving restoration programs and commercial cultivation of medicinal orchids and releasing the pressure on wild populations from harvesting.

Abstract

Recent years have seen a rapid increase in the study of coral-associated gastropods. In particular, the description of several new species in conjunction with their host specificity or dietary variability, has raised questions pertaining to their impact on reef health. These corallivores have been labelled as both ‘parasite’ and ‘predator’ by different studies, due to the tendency of some species to entirely consume their ‘host’ corals. Here we present new findings of corallivory and parasitism based on surveys conducted on the reefs of Koh Tao, Gulf of Thailand. A total of 6566 corals were assessed for their tendency to host gastropods of the nudibranch genus Phestilla and the caenogastropod family Epitoniidae. Thirteen gastropod species were found to be associated with 20 scleractinian coral species, including six that do not match the original description of previously known taxa. Herein we describe one of them, the first nudibranch proven to be associated with corals of the scleractinian genus Acropora and discuss conservation implications of these coral/gastropod relationships. Additionally, we explore the complex topic of defining these relationships as parasitic versus predatory and the merits of using these labels to better understand the ecology of these relationships.

Intercropping of legumes and cereals has many benefits to both plant partners. In this study, the effect of legume-maize intercropping on plant growth, grain yield and N₂ fixation of six legumes was assessed using the ¹⁵N natural abundance and ureide techniques. For this, a field experiment involving six legume species and two cropping systems was established at the Malkerns Research Station, Eswatini during the 2017/2018 cropping season. Based on the ¹⁵N isotopic and ureide analysis, the six test legumes respectively obtained 39.06 – 70.19% and 16.46 – 55.79% of their N nutrition from symbiosis. The amounts of N-fixed ranged from 12.66 to 66.57 kg ha⁻¹. In general, high amount of N-fixed by legumes correlated strongly with greater shoot dry matter accumulation (r = 0.7981; p < 0.001) and high grain yield (r = 0.5905; p < 0.001), indicating the importance of N₂ fixation in plant growth and reproduction. Legumes grown under monocropping recorded higher plant growth, symbiotic performance and grain yield when compared to those grown in mixed culture with maize. However, shoot %Ndfa was much higher under intercropping than sole cropping due to competition by cereal and legume for soil N. Components of maize yield were similar for the two cropping systems. The %N derived from fixation and %relative ureide-N abundance were significantly correlated (r = 0.4005; p < 0.001), indicating that the ¹⁵N natural abundance technique and the ureide method were complementary in measuring N₂ fixation in the test legumes. These results have provided some insights on the impact of cropping system on plant growth, symbiotic performance and grain yield of six selected legumes.

Abstract

Obligate endosymbionts have a significant impact on the physiology and ecology of their insect hosts and consequently have played an important role in their diversification and evolution. Auchenorrhyncha is a sap-feeding insect group that includes cicadas, spittlebugs, leafhoppers, treehoppers, and planthoppers, some of which are well-studied vectors of plant pathogens causing important diseases. Here, we review the obligate symbiotic systems in Auchenorrhyncha. First, we address the diversity of obligate endosymbionts, illustrating the complex scenario characterised by replacements, new acquisitions, and loss of endosymbionts along evolution. Then, we describe the mechanisms that allowed maintaining these long-term associations. Also, we attend to the functional interdependence between host and obligate endosymbionts and how insect hosts support and regulate them. Moreover, we discuss current research that considers the disruption of host-endosymbionts associations as a novel strategy to control these sap-feeding insects. Finally, we suggest directions for further studies regarding obligate mutualistic relationships as well as other symbiotic systems that could be helpful in increasing the knowledge of the complex interactions between Auchenorrhyncha and their associated microbes.

The intracellular bacteria Wolbachia pipientis infects arthropods and filarial nematodes and is able to manipulate host reproduction. It has been reported an association between parthenogenesis and Wolbachia infection in weevils from the tribe Naupactini. A curing experiment suggested that a threshold density of Wolbachia is required for parthenogenetic reproduction to occur. The aim of this study was to analyze Wolbachia infection status and density in two sexually reproducing species from the tribe Naupactini, Naupactus xanthographus and Naupactus dissimulator. Wolbachia infection was detected in individuals from both species in several geographic locations, not being fixed. Quantification through real time PCR confirmed that Wolbachia loads in sexual species were significantly lower than in parthenogenetic ones; these results support the hypothesis of a threshold level for parthenogenetic reproduction to occur in Naupactini weevils. Strain typing showed that both sexual species carry wNau1, the most frequent strain in parthenogenetic Naupactini weevils. In addition, the presence of the WO phage, which might be an important factor regulating infection density in some hosts, was detected in this strain. Finally, Wolbachia wNau1 was located throughout the whole insect body, which is in agreement with the idea of a recent acquisition by horizontal transfer of wNau1 across the tribe Naupactini.

The exact nature of the relationship between symbiont fauna and their hosts is often unclear, but knowing more about these intricate ecological interactions is vital to understand the trophic positions of host-associated fauna, and can aid in accurate constructions of food-webs on coral reefs. Scleractinian corals are hosts to hundreds of symbiont taxa, including fish and many invertebrate species. Some of these associated fauna are beneficial to their coral host(s), whereas other taxa can have detrimental effects, yet their impact is often difficult to determine. Coral-dwelling gall crabs (Cryptochiridae) are obligate, often host-specific, symbionts of scleractinian corals but the nature of this relationship is still under debate. Three Atlantic gall crab species (Kroppcarcinus siderastreicola, Opecarcinus hypostegus and Troglocarcinus corallicola) and their coral hosts’ tissue/mucus were collected from reefs in Guadeloupe. Stable carbon and nitrogen isotope values were measured for 57 crabs inhabiting host coral colonies belonging to seven different coral species (although only 27 colonies from five coral species were collected), alongside other potential food sources (epilithic algal matrix, plankton and particulate organic matter). The carbon and nitrogen isotope values of gall crabs relative to those of their respective coral host(s) and other possible food sources showed that coral tissue/mucus was the main food source for the crabs. The results of the mixing models further supported this finding, suggesting that corals are responsible for 40–70% of the crabs’ diet. In T. corallicola, the isotopic signature differed significantly between sexes, possibly caused by the high sexual dimorphism observed in this species. Here we showed that Atlantic gall crabs mainly dine on coral tissue and/or mucus excreted by their coral hosts, highlighting their nutritional dependence on their host. However, since coral mucus is continuously exuded by scleractinians, hence the energetic or metabolic drain for corals is expected to be minimal. Gall crabs depend on their coral hosts for settlement cues as larvae, for habitat as adults and - highlighted by this study - for food, essential for their subsistence. This obligate dependence on their hosts for all parts of their life makes them extremely vulnerable to reef degradation, and underlines the importance in understanding the exact nature of a relationship between symbiont and coral host.