Symbiosis最新文献

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.

Abstract

Numerous marine invertebrates form symbiotic relationships with single-celled algae, termed “photosymbioses”, and the diversity of these interactions is likely underestimated. We examined Phidiana lynceus, a cladobranch sea slug that feeds on photosymbiotic hydrozoans. We assessed its ability to acquire/retain algal symbionts by examining specimens in starvation, finding that P. lynceus is able to incorporate and retain symbionts for up to 20 days. Examining body size during starvation revealed that P. lynceus does not receive enough energy from hosting symbionts to maintain its body mass let alone grow. Intact symbionts were still present in deceased specimens, indicating that P. lynceus does not digest all of its symbionts, even when starving to death. We also examined slug behavior in the field and lab to determine if it seeks light to facilitate photosynthesis, which could provide energetic and oxygenic benefits. In the field, slugs were always observed hiding under stones during the day and they displayed light avoidance in the lab, suggesting this species actively prevents photosynthesis and the benefits it could receive. Lastly, we measured their metabolic rates during the day and night and when treated with and without a photosynthetic inhibitor. Higher metabolic rates at night indicate that this species displays nocturnal tendencies, expending more energy when it emerges at night to forage. Paradoxically, P. lynceus has evolved all of the requisite adaptations to profit from photosymbiosis but it chooses to live in the dark instead, calling into question the nature of this symbiosis and what each partner might receive from their interaction.

Insects can establish a variety of symbiotic associations with bacteria that can have a significant impact on their evolutionary ecology. Some bacterial lineages are particularly pervasive as symbiotic associates. This is the case of the Sodalis genus, whose members have established independent, maternally transmitted symbioses in diverse insect taxa. The first members of the genus were isolated and studied some thirty years ago in tsetse flies, where they evolved as heritable facultative symbionts. Since then, numerous symbiotic associations involving members of the genus have been documented, some of which have evolved into strictly host-dependent mutualistic associations. The genus also includes members circulating freely in the environment, which can be pathogenic, have extensive metabolic capabilities and constitute a potential reservoir of new insect symbionts. In this review, we cover more than thirty years of literature to highlight how the diversity of the Sodalis genus described so far embodies the different degrees of host dependence and anatomical integration that bacteria can experience over the course of their evolution with insects. We discuss the propensity of Sodalis bacteria to embrace an endosymbiotic lifestyle, how this feature can be used to understand the nascent stages of bacterial endosymbiosis, and how Sodalis bacteria can be used to address fundamental and applied research issues. Throughout the review, emphasis is placed on research gaps that need to be filled to better address these aspects. We also draw attention to previously overlook facets of the genus that deserve further investigation, such as the potential role of Sodalis bacteria in wood digestion in certain insects, or the nature of their interaction with plants.

Arbuscular mycorrhizal fungi (AMF) promote water and mineral nutrients uptake by plant roots, which can reduce the chemical fertilizer inputs in crop production. To gain better insight into the comparative effect of different strains of AMF in improving tomato performance at morphological and physiological levels, seedlings of two tomato cultivars (i.e., Better Boy and Roma) were inoculated with four strains of Glomus mosseae (i.e., HS 1–2, BEG 12, BEG 55, and BEG 54) under greenhouse conditions. Results showed that tomato growth and yield varied largely depending on the mycorrhizal strain and tomato cultivar, with wide variations in root colonization ranging from 5.30 to 78.63%. Overall, mycorrhization with BEG 54 showed significantly better tomato performance when compared to the BEG 55, HS 1–2 and BEG 12 strains. In the case of cultivars, Better Boy performed better than Roma cultivar in terms of growth, physiological traits, yield, and fruit quality. The highest plant height, dry matter, nitrogen, phosphorus, potassium, chlorophyll a, chlorophyll b, AMF colonization, yield, fruit juice, ascorbic acid, and titratable acidity contents were recorded in Better Boy cultivar while the highest stem diameter was found in Roma cultivar. Taken together, AMF colonization suggested a promising approach for large-scale tomato production by efficient absorption and utilization of nutrients, and encouraging plants’ symbiotic relationships with soil microorganisms.