Nutrient Exchange Research Articles

Thermotolerant coral-algal mutualisms maintain high rates of nutrient transfer while exposed to heat stress.

Symbiotic mutualisms are essential to ecosystems and numerous species across the tree of life. For reef-building corals, the benefits of their association with endosymbiotic dinoflagellates differ within and across taxa, and nutrient exchange between these partners is influenced by environmental conditions. Furthermore, it is widely assumed that corals associated with symbionts in the genus Durusdinium tolerate high thermal stress at the expense of lower nutrient exchange to support coral growth. We traced both inorganic carbon (H13CO3-) and nitrate (15NO3-) uptake by divergent symbiont species and quantified nutrient transfer to the host coral under normal temperatures as well as in colonies exposed to high thermal stress. Colonies representative of diverse coral taxa associated with Durusdinium trenchii or Cladocopium spp. exhibited similar nutrient exchange under ambient conditions. By contrast, heat-exposed colonies with D. trenchii experienced less physiological stress than conspecifics with Cladocopium spp. while high carbon assimilation and nutrient transfer to the host was maintained. This discovery differs from the prevailing notion that these mutualisms inevitably suffer trade-offs in physiological performance. These findings emphasize that many host-symbiont combinations adapted to high-temperature equatorial environments are high-functioning mutualisms; and why their increased prevalence is likely to be important to the future productivity and stability of coral reef ecosystems.

Habitat heterogeneity drives arbuscular mycorrhizal fungi and shrub communities in karst ecosystems

Arbuscular mycorrhizal fungi (AMF) constitute one of the factors that regulate the success of vegetation restoration. Karst ecosystems are heterogenous in nutrient content and plant communities because of preferential water fluxes within cracks and gullies in the soil parent material. The effects of habitat on soil nutrients, shrub, and AMF diversity in karst ecosystems are yet to be established. Thus, we investigated the diversity of shrubs and AMF within three habitats: i) rocky soil surface (Rock), ii) soil surface (Soil), and iii) rocky gully (Gully) in a typical karst shrub ecosystem. We observed that AMF diversity was independent of the sampling location, whereas AMF abundance and the shrub Shannon index increased with sampling distance, reaching a plateau in a sampling area of 1000 m2. The AMF community composition was driven by dominating shrubs (Vitex negundo, Tirpitzia ovoidea). Higher shrub diversity and AMF abundance occurred in Rock than in Soil and Gully areas, suggesting higher habitat heterogeneity in Rock areas. Based on co-occurrence network analysis, interactions with a high link number among the AMF taxa were stronger in Rock than in Gully because the network complexity in the Rock areas strongly depended on symbiosis with AMF taxa to cope with high habitat heterogeneity. The Random forest model revealed that AMF abundance was mainly affected by available phosphorous, total potassium, and shrub diversity. Available phosphorous, soil pH, and exchangeable Ca2+, rather than plant diversity, were the main factor controlling AMF community composition. Overall, the results suggest that the increase in shrub diversity raised AMF abundance and richness, and strengthened the interactions among AMF taxa because of nutrient exchange. Thus, increasing habitat heterogeneity with abundant shrub diversity, but soil nutrient limitation, enriches AMF abundance and diversity.

Response of Nitrogen Removal Performance and Microbial Distribution to Seasonal Shock Nutrients Load in a Lakeshore Multicell Constructed Wetland

Multicell constructed wetlands (MCWs) on lakeshores are a prospective treatment technique. However, the factors affecting the nutrient removal performance of lakeshore MCWs at the field scale are unclear. This study chose a field-scale lakeshore MCW with the highest mass removal efficiency (approximately 49,175.12 mg m−2 day−1) for total nitrogen removal in the wet season to investigate the response of nitrogen removal and microbial distribution to seasonal shock nutrients load. The mass loading rates in the wet season were as high as 43~72 times over those in the dry season. Hence, a storage pond (SP), as a forebay retention cell, was necessary to mitigate the shock loads of the influent, which is beneficial to nitrogen removal of the MCW system. The two major genera in the sediments are heterotrophic nitrification–aerobic denitrification bacteria, and the abundance and species of the nitrogen-related functional genera were higher in the wet season than the dry season. According to the results of redundancy analysis, the hydraulic residence time (29.4%, F = 2.2, p < 0.1) and hydraulic loading rate (85.9, F = 36.5, p < 0.05) were the major factors explaining microbial community variation, instead of environmental factors (temperature, pH, and dissolved oxygen). The shock loads of influent and the periodic saturation in sediments contributed to a complicated oxygen and nitrogen nutrient exchange environment resulting in higher abundance and species of nitrogen-related microbes, which is beneficial to nitrogen removal in lakeshore MCWs. The results provided a scientific basis for the optimal design of constructed wetlands on lakeshores.

Control of arbuscule development by a transcriptional negative feedback loop in Medicago

Most terrestrial plants establish a symbiosis with arbuscular mycorrhizal fungi (AMF), which provide them with lipids and sugars in exchange for phosphorus and nitrogen. Nutrient exchange must be dynamically controlled to maintain a mutually beneficial relationship between the two symbiotic partners. The WRI5a and its homologues play a conserved role in lipid supply to AMF. Here, we demonstrate that the AP2/ERF transcription factor MtERM1 binds directly to AW-box and AW-box-like cis-elements in the promoters of MtSTR2 and MtSTR, which are required for host lipid efflux and arbuscule development. The EAR domain-containing transcription factor MtERF12 is also directly activated by MtERM1/MtWRI5a to negatively regulate arbuscule development, and the TOPLESS co-repressor is further recruited by MtERF12 through EAR motif to oppose MtERM1/MtWRI5a function, thereby suppressing arbuscule development. We therefore reveal an ERM1/WRI5a–ERF12–TOPLESS negative feedback loop that enables plants to flexibly control nutrient exchange and ensure a mutually beneficial symbiosis.

Point of Zero Charge of Soils - It’s Dynamics under Fertilizer Management Practices and Nutrient Availability

Aims: To study the dynamics of point of zero charge of different soil types and determine the availability of nutrients under the influence of specific fertilizer management practices.
 Study Design: Completely Randomized Design.
 Place and Duration of Study: Department of Soil Science, Assam Agricultural University, Jorhat, Assam; between March 2020 and December 2021.
 Methodology: We estimated the point of zero charge (PZC) components, i.e., the point of zero salt effect (PZSE) and point of zero net charge (PZNC) in six surface soil samples [black soil (Vertisol), laterite soil (Alfisol), red soil (Alfisol) of Odisha, and alluvial soils belonging to Entisol, Inceptisol, and Alfisol of Assam, India] through potentiometric titration and ion retention methods respectively. The soils were subjected to four specific fertilizer management practices under laboratory incubation, viz., FYM @ 5 t ha-1 (T1), NPK @ 80:40:40 for Odisha soils and 60:20:40 for Assam soils (T2), T1 + T2 (T3) and T3 + Lime requirement/ Gypsum requirement (T4). The PZC components and availability of nutrients were determined at 15 and 30 days after incubation.
 Results: The PZSE values of the soils ranged from 2.18 to 4.70, while PZNC values were achieved at relatively lower pH ranging from 2.03 to 4.10. Highest values of PZSE and PZNC were recorded under treatment T2 followed by T3, T4 and T1 for all the incubated soil samples, however there was a decrease in the PZC values with increase in days of incubation. Comparatively, the treatment T4 resulted as the most ideal fertilizer management practice. Besides providing optimum amount of primary and maximum amount of secondary nutrients, T4 regulated the PZC values favouring minimal loss of nutrients and enhanced nutrient use efficiency. The availability of nutrient ions is influenced by the difference between soil solution pH and PZC values of the soil, which recorded to be highest for Vertisol (OS1), followed by Entisol (AS1), Inceptisol (AS2), and Alfisol (AS3, OS2, OS3) soil orders.
 Conclusion: The exchange and availability of cationic nutrients get enhanced due to higher CEC in soils with high clay and organic matter percentage. The pH of these soils must therefore be regulated for better availability of anionic nutrients. Highly weathered soil of Alfisol order exhibit optimal CEC over a narrow pH range, favouring better availability of anionic nutrients and hence simultaneously require frequent fertilizer application along with organic manures for the enhanced retention, mobility and availability of nutrients in soil.

Syntrophic Interactions Ameliorate Arsenic Inhibition of Solvent-Dechlorinating Dehalococcoides mccartyi.

Interactions and nutrient exchanges among members of microbial communities are important for understanding functional relationships in environmental microbiology. We can begin to elucidate the nature of these complex systems by taking a bottom-up approach utilizing simplified, but representative, community members. Here, we assess the effects of a toxic stress event, the addition of arsenite (As(III)), on a syntrophic co-culture containing lactate-fermenting Desulfovibrio vulgaris Hildenborough and solvent-dechlorinating Dehalococcoides mccartyi strain 195. Arsenic and trichloroethene (TCE) are two highly prevalent groundwater contaminants in the United States, and the presence of bioavailable arsenic is of particular concern at remediation sites in which reductive dechlorination has been employed. While we previously showed that low concentrations of arsenite (As(III)) inhibit the keystone TCE-reducing microorganism, D. mccartyi, this study reports the utilization of physiological analysis, transcriptomics, and metabolomics to assess the effects of arsenic on the metabolisms, gene expression, and nutrient exchanges in the described co-culture. It was found that the presence of D. vulgaris ameliorated arsenic stress on D. mccartyi, improving TCE dechlorination under arsenic-contaminated conditions. Nutrient and amino acid export by D. vulgaris may be a stress-ameliorating exchange in this syntrophic co-culture under arsenic stress, based on upregulation of transporters and increased extracellular nutrients like sarcosine and ornithine. These results broaden our knowledge of microbial community interactions and will support the further development and implementation of robust bioremediation strategies at multi-contaminant sites.

Successful endothelial monolayer formation on melt electrowritten scaffolds under dynamic conditions to mimic tunica intima

The lack of transplantable tissues and organs as well as the limitations of synthetic implants highlight the need for tissue-engineered constructs to obtain safe, long-lasting, and limitless tissue replacements. Scaffolds for cardiovascular applications, such as for a tissue-engineered vascular graft (TEVG), are thus highly required. For TEVGs, tubular scaffolds should support the formation of confluent endothelial layers in particular under dynamic conditions to prevent thrombosis and maintain hemostasis. For that purpose, a porous and highly diffusible scaffold structure is necessary to allow optimal cell adhesion as well as oxygen and nutrient exchange with the surrounding tissue. Here, we present a three-dimensional-printed scaffold made by a combination of fused deposition modeling (FDM) and melt electrowriting (MEW) out of polycaprolactone that enables monolayer formation and alignment of endothelial cells in the direction of medium flow under a shear stress of up to 10 dyn cm-2. Pore size and coating with human fibrin were optimized to enable confluent endothelial layers on the printed scaffold structures. Cell orientation and shape analysis showed a characteristic alignment and elongation of the tested endothelial cells with the direction of flow after dynamic cultivation. In contrast, melt electrospun scaffolds based on the same CAD design under comparable printing and cultivation conditions were not sufficient to form gapless cell layers. Thus, the new scaffold fabricated by MEW/FDM approach appears most suitable for TEVGs as a template for the innermost vascular wall layer, the tunica intima.

Nanoparticles at the maternal-fetal interface

The increasing production of intentional and unintentional nanoparticles (NPs) has led to their accumulation in the environment as air and ground pollution. The heterogeneity of these particles primarily relies on the NP physicochemical properties (i.e., chemical composition, size, shape, surface chemistry, etc.). Pregnancy represents a vulnerable life stage for both the woman and the developing fetus. The ubiquitous nature of these NPs creates a concern for developmental fetal exposures. At the maternal-fetal interface lies the placenta, a temporary endocrine organ that facilitates nutrient and waste exchange as well as communication between maternal and fetal tissues. Recent evidence in human and animal models identifies that gestational exposure to NPs results in placental translocation leading to local effects and endocrine disruption. Currently, the mechanisms underlying placental translocation and cellular uptake of NPs in the placenta are poorly understood. The purpose of this review is to assess the current understanding of the physiochemical factors influencing NP translocation, cellular uptake, and endocrine disruption at the maternal-fetal interface within the available literature.

Thin and transient meltwater layers and false bottoms in the Arctic sea ice pack—Recent insights on these historically overlooked features

The rapid melt of snow and sea ice during the Arctic summer provides a significant source of low-salinity meltwater to the surface ocean on the local scale. The accumulation of this meltwater on, under, and around sea ice floes can result in relatively thin meltwater layers in the upper ocean. Due to the small-scale nature of these upper-ocean features, typically on the order of 1 m thick or less, they are rarely detected by standard methods, but are nevertheless pervasive and critically important in Arctic summer. Observations during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition in summer 2020 focused on the evolution of such layers and made significant advancements in understanding their role in the coupled Arctic system. Here we provide a review of thin meltwater layers in the Arctic, with emphasis on the new findings from MOSAiC. Both prior and recent observational datasets indicate an intermittent yet long-lasting (weeks to months) meltwater layer in the upper ocean on the order of 0.1 m to 1.0 m in thickness, with a large spatial range. The presence of meltwater layers impacts the physical system by reducing bottom ice melt and allowing new ice formation via false bottom growth. Collectively, the meltwater layer and false bottoms reduce atmosphere-ocean exchanges of momentum, energy, and material. The impacts on the coupled Arctic system are far-reaching, including acting as a barrier for nutrient and gas exchange and impacting ecosystem diversity and productivity.

Impact of varied NPK fertilizer application rates and seed quantities on barley yield and soil nutrient availability in chestnut soil of Azerbaijan

In the Gobustan district of Azerbaijan, the cultivation of barley is influenced by a complex interplay of soil properties, climate change effects, and agricultural practices. This study explores the impact of varying NPK fertilizer application rates and seed quantities, under natural climatic conditions, on barley yield and soil nutrient availability within Chestnut soils. The district's unique Chestnut soils, combined with evolving precipitation patterns due to climate change and the role of agricultural irrigation, create intricate challenges for successful barley farming. The experiment, conducted from 2016 to 2019, utilized a randomized complete block design with four replications to investigate the "Celilabad-19" barley variety. The results reveal a significant positive correlation between nitrogen application and grain yield. Notably, treatment 140-N60P45K45 (140 kg seed rate, 60 kg N/ha, 45 kg P/ha and 45 kg K/ha) demonstrated the highest average grain yield of 5.14 t/ha. The years 2017-2018 exhibited higher yields, possibly due to favorable climate conditions. Soil analyses indicated that higher NPK application rates led to elevated soil nutrient levels. However, nutrient content declined as plants progressed through growth stages, emphasizing the dynamic nutrient exchange between plants and soil. This study underscores the importance of adaptive agricultural strategies that consider climate variability and changing environmental conditions. The findings offer insights into sustainable cultivation practices essential for food security and crop production in the evolving climate of the Gobustan district.

Umbilical cord diameter study on microscopic tissue in gestational diabetes mellitus and its correlation to fresh tissue diameter and fetomaternal parameters

Background: Umbilical cord is the only vital link between the mother and the fetus and is essential for maintaining the fetomaternal exchange of oxygen, nutrients, and waste products. Clinical studies have shown that umbilical cord diameter (UCD) is larger in gestational diabetes mellitus (GDM) and UCD analysis based on microscopic tissue (dry) provides more accurate information. Aims and Objectives: The present study was conducted to measure the UCD using microscopic tissue in GDM and normal cases and ascertain its correlation with fresh tissue (wet) diameter, fetal weight, maternal BMI, and gestational weight gain. Materials and Methods: The study included 111 subjects. They were divided into two groups. Group I consisted of umbilical cords obtained from non-diabetic pregnant women (n=52) and Group II comprised umbilical cords obtained from mothers with GDM (n=59). UCD was measured using Vernier calipers and all the other parameters were assessed through standard methods. Results: UCD in microscopic (P=0.005) and fresh tissues (P=0.0001) was significantly higher in GDM patients. Although microscopic tissue measurements tended to underestimate fresh-tissue measurements of UCD, these measurements had a positive correlation with each other in both groups. UCD also had a statistically significant positive correlation with maternal BMI and a negative correlation with gestational weight gain. Conclusion: UCD in GDM was statistically higher in both microscopic and fresh tissues and thus may be considered for GDM screening. The correlation of wet and dry specimens can also provide useful insights in clinical situations centered around variations in UCD.

Rapid Construction of 3D Biomimetic Capillary Networks with Complex Morphology Using Dynamic Holographic Processing

AbstractMicrovascular networks (MVNs) are crucial transportation systems in living creatures for nutrient distribution, fluid flow, energy transportation and so on. However, artificial manufacturing of MVNs, especially capillary networks with diameters (average 6 ≈ 9 µm), has always been a problem and bottleneck in tissue engineering due to the lack of efficient manufacturing methods. Herein, a dynamic holographic processing method is reported for producing 3D capillary networks with complex biomimetic morphologies. Combining the axial scanning of the focused beam and the dynamic display of holograms, biomimetic bifurcated microtubes, and porous microtubes with programmable morphologies are rapidly produced by two‐photon polymerization (TPP). As a proof‐of‐concept demonstration, porous microtubes are used as 3D capillary network scaffolds for culturing human umbilical vein endothelial cells (HUVECs) to facilitate the exchange of nutrients and metabolites. Endothelial cells around the vascular scaffolds manifest obvious tight connections and 3D coverage after 3 days in vitro, which reveals that the scaffolds play a significant role in the morphology of dense vascularization. This flexible and rapid method of producing capillary networks provides a versatile platform for vascular physiology, tissue regeneration, and other biomedical areas.

Transcriptomic Analysis of CBD-Exposed Rat Placentae Reveals Down-Regulated Angiogenic Pathways and Up-Regulated Metabolic Processes

Following nicotine, cannabis is the most used drug during pregnancy. In utero cannabis exposure is linked to adverse outcomes, including fetal growth restriction. Cannabidiol (CBD), the non-hallucinogenic constituent of cannabis, is perceived as safe for use during pregnancy by ~25% of women. While studies assessing the effects of Δ-9-THC, the other principal cannabinoid in cannabis, have been initiated, research examining the impact of CBD on pregnancy is scarce. The placenta facilitates the exchange of gas, nutrients and waste between the fetus and mother. Our group has recently identified altered placental morphology and reduced fetal growth after in utero CBD exposure in rats. However, the influence of CBD on genes, transcription factors and biological processes in the placenta has not been assessed. This study aimed to identify biological pathways in the placenta that were significantly altered by CBD-exposure and correlate the findings with previously performed histological analysis. Pregnant rats were administered a daily dose of 3 mg/kg CBD or a vehicle control from embryonic day (E) 6.5-18.5. On E19.5, placentae were harvested for transcriptomic analysis. RNA extraction, library construction and bulk RNA sequencing was performed by Genome Quebec. The top differentially expressed genes were analysed using Metascape software, revealing the most up- and down-regulated Gene Ontology (GO) biological process pathways. Down-regulated GO biological processes included tube morphogenesis, angiogenesis, and blood vessel morphogenesis, which supported the angiogenic complications identified by histology. Further, the most significantly up-regulated GO biological processes were metabolic, including peptide, glycoprotein, glycosaminoglycan, and tetrahydrofolate. This is significant, as the histological analysis identified elevated Glut3 expression in the placentae from CBD-exposed pregnancies. Elevated Glut3 in fetal growth restriction is associated with changes to metabolic pathways. Consequently, additional studies will include analysis of CBD-exposed rat trophoblast cells to establish whether metabolic changes may underlie the altered morphology identified in CBD-exposed placentae.

Variability of the phytoplankton biomass in the southwestern Bay of Bengal from 2003 to 2018

The Bay of Bengal (BoB) has distinctive hydrological characteristics, and various physical mechanisms strongly influence the growth of phytoplankton in this region. In this work, we investigated the monthly and interannual variations of phytoplankton biomass (PB) in the southwestern (SW) BoB (78–88°E, 0–15°N) utilizing satellite data from 2003 to 2018. Bivariate wavelet coherence (BWC) and multiple wavelet coherence (MWC) analyses were conducted to assess the temporal fluctuations in various physical oceanographic parameters. The findings revealed that wind speed (WSP) and sea surface temperature (SST) were the main drivers for the monthly variations of chlorophyll-a (Chl-a). The southwest monsoon promoted the formation of upwelling by offshore Ekman transport via the southwest monsoon current (SMC) and the upward Ekman pumping induced by the strong positive wind stress curl, which brought nutrient-rich, cold waters from the subsurface to the surface, stimulating phytoplankton growth. The BWC analysis results identified WSP as the most effective individual factor accounting for the interannual fluctuations in Chl-a concentrations. The MWC analysis results unraveled that the combinations of WSP–SST, WSP–Niño 3.4, WSP–EPV, and WSP–DMI exhibited the strongest relationships with the changes in Chl-a in the SW BoB. The PB in 2015 demonstrated abnormally low values. The El Niño event in 2015 substantially weakened the southwest monsoon and current, possibly weakening the Ekman transport on the southern coast of Sri Lanka and India. Moreover, an abnormally intensified anticyclonic eddy occurred in this region. These processes disrupted the vertical exchange of nutrients, obstructing the vertical transport of nutrient-enriched subsurface waters and leading to abnormally decreased levels of Chl-a in 2015.

Connectivity as a driver of river-floodplain functioning: A dynamic, graph theoretic approach

Connectivity is a crucial property of the river-floodplain ecosystem. Reduction of connectivity, fragmentation and isolation effects, impacting ecological functions and biodiversity, is one of the most critical threats to floodplain systems. We use a graph theoretical approach for analyzing possible transport pathways in the system (directed, undirected, overland, seepage) and relate them to ecosystem functions in a river-floodplain system impacted by engineering structures (Danube River, Vienna, Austria). We studied essential ecological functions using indicators on sediment composition and quality, hydrochemical conditions, and macrophyte coverage. Our results indicate that sediment transport and composition are widely driven by directional flow and connectivity. In contrast, the exchange of water and nutrients is dominated by seepage exchange in the system. Macrophytes are dominating in water bodies which are not relevant for directed transport. The graph theoretical approach solely based on remotely sensed data can be used to classify floodplain water bodies related to their essential function and importance in the network and identify main deficits and potential restoration measures. It can, therefore, be an essential tool for prioritizing systems for management measures and restoration actions.

Biomimetic design and fabrication of PEEK and PEEK/CF cage with minimal surface structures by fused filament fabrication

The interbody fusion cages are critical implants in spinal fusion surgeries, which stabilize the spine and treat pains resulting from degenerative disc disease. The commercial used poly (ether-ether-ketone) (PEEK) cages are non-porous and manufactured by machining, which cause material waste and insufficient bioactivity. Fused filament fabrication (FFF) technology provides opportunities to fabricate fusion cages with specific shape and intricate porous architectures for bone ingrowth and nutrient exchange. Herein, PEEK-based lattice structures are designed and firstly fabricated by FFF based on three minimal surfaces including Schwarz P (P), Diamond (D) and Gyroid (G). The effects of cellular architecture and unit cell on the compressive properties are investigated. The results demonstrate that D and G surfaces possess superior load-carrying and energy absorption capacity. The prototyping defects in PEEK lattices were lesser than those in PEEK/CF samples. Also, it is notable that the compression performance of FFF-printed samples exhibited a strong anisotropy depending on the printing direction. After printing, annealing is an effective post treatment to further improve the crystallinity and compressive strength of PEEK lattice surfaces. Therefore, the novel PEEK porous structures with optimized mechanical performance show great potentials in the applications as fusion cage implants.

Sugar metabolism and 14-3-3 protein genes expression induced by arbuscular mycorrhizal fungi and phosphorus addition to response drought stress in Populus cathayana

Sugar, as a nutrient exchange substance between arbuscular mycorrhizal (AM) fungi and host plants, plays an important role in the abiotic stress response of mycorrhizal plants. This experiment aimed to study the effects of AM fungi and phosphorus (P) addition on the sugar metabolism and 14-3-3 gene expression of Populus cathayana under drought stress. The results showed that drought affects the process of sugar metabolism by increasing the activities of amylase and invertase, resulting in the decrease of starch content in leaves and roots and the accumulation of soluble sugars (including reducing sugar and sucrose) in roots. Under drought stress, the activity or content of sucrose synthetase, sucrose phosphate synthase, acid invertase, alkaline invertase, reducing sugar, soluble sugar, sucrose, and starch in the root showed the best mycorrhizal effect at the 100 mg P level. The expression levels of the 14-3-3 genes (PcGRF10 and PcGRF11) were significantly increased by mycorrhizal induction under drought stress. These levels were positively correlated with SS, SPS, sucrose, and starch phosphorylase in leaves, as well as with almost all sugar metabolism indicators in roots. However, they were negatively correlated with starch content in both leaves and roots. Sugar metabolism and 14-3-3 protein gene expression were induced by AM fungi and P addition in response to drought stress. The 14-3-3 genes induced by AM fungi may be involved in participating in osmotic regulation during drought stress. This study provides a new idea for the mechanism of sugar metabolism of mycorrhizal plants in arid regions.

Regulation of mycorrhizal colonization under stress in tomato depends on symbiotic efficiency

The mutualistic symbiosis between plants and arbuscular mycorrhizal (AM) fungi is based on a balanced nutrient exchange between both partners, with the plant achieving improved nutrition and stress tolerance. The symbiosis is finely-tuned according to plant’s needs and surrounding conditions, usually through phytohormonal signaling. Thus, environmental conditions or stress factors modulating phytohormone signaling may influence the symbiosis. This study compares the colonization abilities of 2 AM fungal species, Funneliformis mosseae and Rhizophagus irregularis, independently or in combination, in tomato plants subjected to different stress conditions. These included salt stress and systemic defense activation by aboveground application of the defense-related hormones methyl jasmonate, abscisic acid and salicylic acid. The results show that root colonization by the two fungal species differs depending on the stress treatment. Nutrient and transcriptional analyses revealed that changes in colonization correlated with differential regulation of nutrient exchange, plant defensive responses, and symbiosis regulatory genes. Specifically, under salt stress R. irregularis colonization decreased, while F. mosseae colonization was promoted. These differential regulation of colonization under stress positively correlated with changes in the functionality of the symbiosis. Overall, the results support that the benefits provided by each AM fungi influence carbon reward and determines the control of root colonization by the host plant.

Premetastatic Niche Mimicking Bone-On-A-Chip: A Microfluidic Platform to Study Bone Metastasis in Cancer Patients.

Primary cancer modulates the bone microenvironment to sow the seeds of dormancy and metastasis in tumor cells, leading to multiple organ metastasis and death. In this study, 3D printing and bone-on-a-chip (BOC) are combined to develop a BOC platform that mimics the pre-metastatic niches (PMNs) and facilitates elucidation of the interactions between bone-resident cells and metastatic tumor cells under the influence of primary cancer. Photocrosslinkable gelatin methacrylate (GelMA) is used as a 3D culturing hydrogel to encapsulate cells, and circulate tumor culture medium (CM) adjacent to the hydrogel to verify the critical role of mesenchymal stem cells (MSCs) and osteoclasts (RAW264.7s). Three niches: the dormancy niche, the perivascular niche, and the "vicious cycle" niche, are devised to recapitulate bone metastasis in one chip with high cell viability and excellent nutrient exchange. With respect to tumor dormancy and reactivation, the invadopodia formation of A549 lung cancer cells in communication with MSCs and RAW264.7 via the cortactin pathway is researched. As a proof of concept, the functionality and practicality of the platform are demonstrated by analyzing the invadopodia formation and the influence of various cells, and theestablishment of the dynamic niches paves the way to understanding PMN formation and related drug discovery.

Inhibitory to non-inhibitory evolution of the ζ subunit of the F1FO-ATPase of Paracoccus denitrificans and α-proteobacteria as related to mitochondrial endosymbiosis.

Introduction: The ζ subunit is a potent inhibitor of the F1FO-ATPase of Paracoccus denitrificans (PdF1FO-ATPase) and related α-proteobacteria different from the other two canonical inhibitors of bacterial (ε) and mitochondrial (IF1) F1FO-ATPases. ζ mimics mitochondrial IF1 in its inhibitory N-terminus, blocking the PdF1FO-ATPase activity as a unidirectional pawl-ratchet and allowing the PdF1FO-ATP synthase turnover. ζ is essential for the respiratory growth of P. denitrificans, as we showed by a Δζ knockout. Given the vital role of ζ in the physiology of P. denitrificans, here, we assessed the evolution of ζ across the α-proteobacteria class. Methods: Through bioinformatic, biochemical, molecular biology, functional, and structural analyses of several ζ subunits, we confirmed the conservation of the inhibitory N-terminus of ζ and its divergence toward its C-terminus. We reconstituted homologously or heterologously the recombinant ζ subunits from several α-proteobacteria into the respective F-ATPases, including free-living photosynthetic, facultative symbiont, and intracellular facultative or obligate parasitic α-proteobacteria. Results and discussion: The results show that ζ evolved, preserving its inhibitory function in free-living α-proteobacteria exposed to broad environmental changes that could compromise the cellular ATP pools. However, the ζ inhibitory function was diminished or lost in some symbiotic α-proteobacteria where ζ is non-essential given the possible exchange of nutrients and ATP from hosts. Accordingly, the ζ gene is absent in some strictly parasitic pathogenic Rickettsiales, which may obtain ATP from the parasitized hosts. We also resolved the NMR structure of the ζ subunit of Sinorhizobium meliloti (Sm-ζ) and compared it with its structure modeled in AlphaFold. We found a transition from a compact ordered non-inhibitory conformation into an extended α-helical inhibitory N-terminus conformation, thus explaining why the Sm-ζ cannot exert homologous inhibition. However, it is still able to inhibit the PdF1FO-ATPase heterologously. Together with the loss of the inhibitory function of α-proteobacterial ε, the data confirm that the primary inhibitory function of the α-proteobacterial F1FO-ATPase was transferred from ε to ζ and that ζ, ε, and IF1 evolved by convergent evolution. Some key evolutionary implications on the endosymbiotic origin of mitochondria, as most likely derived from α-proteobacteria, are also discussed.