Symbiosis最新文献

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.

Known as the Roscoff worm or mint-sauce worm, Symsagittifera roscoffensis is an Acoel distinguishable due to the presence of symbiotic alga Tetraselmis convolutae, held beneath the epidermis. Isolated populations of S. roscoffensis span a broad geographical range along the north-eastern Atlantic coast, from Wales to Portugal. The only known population of the worm in the United Kingdom was discovered in Wales decades ago, but very little research has been conducted since. For 13 months, we measured how environmental conditions such as temperature, salinity and light intensity coincided with population size at the Welsh field site. To establish phylogenetic relationships among the different populations and their algal symbionts, we designed new polymerase chain reaction (PCR) oligonucleotides to assess the nucleotide diversity of the mitochondrial cytochrome c oxidase I subunit (COI) gene in gDNA extracted from representative worms across their known range (Wales, France, Portugal, Spain, and Guernsey). We also targeted the 18S rRNA gene of their algal symbiont, Tetraselmis convolutae. We observed temporal shifts in environmental factors coinciding with fluctuating worm colony size, notably temperature. Based on the molecular data, the worm exhibited different ecotypes across locations, while the algal symbiont showed little genetic variation.

The rhizobial and the arbuscular mycorrhizal symbioses are present on legume roots and lead to local and systemic transcriptional changes of common and specific plant genes. Among them, some small GTPase proteins called ROPs (Rho of plants) have been shown to be involved in the establishment of the legume-rhizobia interaction. In this study, we aimed to characterise the effects of LjROP3 knockdown in Lotus japonicus on plant physiology and expression of symbiosis-related genes after single and dual inoculation with rhizobia and arbuscular mycorrhizal fungus. In wild-type (Gifu) plants, the dual inoculation increased the shoot and root dry weight, nitrogen (derived from symbiosis) and phosphate content, and the number of arbuscules or nodules compared with single inoculation treatments. In addition, we observed a decrease in the expression of genes encoding the mycorrhizal transcription factors LjRAM1 and LjRAM2, and the downstream genes involved in ammonium (LjAMT2.2) and phosphate (LjPT4 and LjPT8) uptake by the plant at the arbuscule level when the dual inoculation was compared with fungal inoculation. An alteration in the expression of the Nod factor receptor LjNFR1, but not of LjNFR5, was measured in wild-type (Gifu) L. japonicus plants compared to rop3 plants under dual inoculation. We have also measured a reduction in the expression of genes encoding rhizobial and mycorrhizal transcription factors (LjNIN and LjRAM1), and of the downstream mycorrhizal genes involved in ammonium (LjAMT2.2) and phosphate (LjPT4 and LjPT8) uptake by the plant at the arbuscule level. In addition, the expression of AM fungal genes encoding nutrient transporters (known to be expressed at the arbuscule level) was also altered. In conclusion, despite altered expression of plant genes involved in the functioning of the symbioses, and associated with a reduction in the number of nodules and arbuscules, knockdown of LjROP3 did not alter plant growth and nutrition under dual inoculation, suggesting that the beneficial effects of the dual symbiosis were maintained.

The use of biological inoculants in replacement of the application of chemical fertilizers is a desirable strategy taking into account it is more sustainable and economically less costly. Considering that agricultural practices can produce effects on soil microbial communities associated to the plant crops, the objective of this study was to analyze and compare the effect of these two practices on the structure of the rhizobacterial community of peanut and maize plants. For this purpose, microcosm assays were performed in which peanut and maize plants were inoculated individually with native peanut phosphate solubilizing strains or chemical fertilized with phosphorus, nitrogen, zinc and sulphur. At the beginning and at the end of the assays, samples of rhizospheric soil DNA were obtained and the structure of the rhizospheric bacterial community was analyzed by high-throughput sequencing of the 16S rRNA gene by using Illumina MiSeq platform. The results obtained indicated that the structures of the rhizospheric bacterial communities were different depending on plant type. It was possible to observe changes with respect to the initial bacterial structure in all taxonomic levels analyzed of all treatments. The more notorious structural changes of bacterial community were observed in those rhizospheres exposed to chemical fertilizers, mainly in soil samples associated to maize plants. The rhizospheric bacterial community of peanut showed to change mainly with plant growth. In conclusion, the rhizobacterial community structure is highly dynamic and influenced by different factors such as type of plant, the fertilizer input and bio-inoculant applied.

Plants are exposed to various abiotic stresses, which lead to crop losses and become a significant threat to agriculture worldwide. To survive, they have developed a range of mechanisms throughout their life cycle. While they develop immunity against stressors through their metabolic and hormonal pathways, as another strategy, they can also modify their environment by interacting with symbiotic microorganisms involved in the critical pathways for plant health. Several beneficial microorganisms can be used as plant stimulants to augment plant health and growth. Therefore, elucidating the cause-effect relationship and possible roles of critical players during plant–microbe interaction may help us better understand the usage of microorganisms for plant benefits. The presented review discusses the molecular mechanisms regulating the responses of plants and their environment during plant–microbe interactions. We focus on the potential roles of plant heterotrimeric G-proteins and small RNAs as inside players and the possible roles, connections, and effects of microalgae and pollinators as outside players/elements during plant–microbe interactions under abiotic stress. Utilizing microbial inoculants with a better combination of endophytes based on various plant species/populations under different environmental conditions is critical for successful field applications. The current knowledge in this review may provide a detailed assessment to gain insight into unraveling different parameters for efficient use of the endophytes on plants/crops to address food security challenges and mitigate the impact of climate change on agriculture.

The knowledge of the interactions between endophytic entomopathogenic fungi and forage plants and their influence on Spodoptera frugiperda, an emerging pest of pastoral systems, is important to elucidate the multifunctionality of these microorganisms and their benefits to agroecosystems. This study investigated the influence of endophytic colonization with different isolates of Metarhizium anisopliae on Cynodon dactylon (L.) Pers (Poaceae) cv. Tifton 85 on biological and behavioral aspects of S. frugiperda. The application of a suspension of isolates (1 × 10⁸ conidia ml⁻¹) to the base (soil drench) of C. dactylon seedlings was effective to promote endophytic colonization. Spodoptera frugiperda caterpillars fed throughout their larval stage with leaves of plants colonized endophytically by the three isolates studied (CEPAF_ENT 25, CEPAF_ENT 27, and IBCB 425) of M. anisopliae showed considerable reduction in their biological performance, especially in parameters of their fertility life table. However, the tested isolates did not show pronounced effects on feeding and oviposition preference, although there was a trend of preference of caterpillars and moths for colonized plants, especially in no-choice tests. Thus, applications of mycoinsecticides based on M. anisopliae for the management of the spittlebug complex (its main use currently) may lead to the endophytic colonization of C. dactylon cv. Tifton 85 and influence S. frugiperda population density as well as the impact this pest causes to pastures. The isolates used in this study exhibit multiple spectrums of action and potential to produce new biological products for the market.