Toxoplasma gondii scavenges mammalian host organelles through the usurpation of host ESCRT-III and Vps4A.

Intracellular pathogens exploit cellular resources through host cell manipulation. Within its nonfusogenic parasitophorous vacuole (PV), Toxoplasma gondii targets host nutrient-filled organelles and sequesters them into the PV through deep invaginations of the PV membrane (PVM) that ultimately detach from this membrane. Some of these invaginations are generated by an intravacuolar network (IVN) of parasite-derived tubules attached to the PVM. Here, we examined the usurpation of host ESCRT-III and Vps4A by the parasite to create PVM buds and vesicles. CHMP4B associated with the PVM/IVN, and dominant-negative (DN) CHMP4B formed many long PVM invaginations containing CHMP4B filaments. These invaginations were shorter in IVN-deficient parasites, suggesting cooperation between the IVN and ESCRT. In infected cells expressing Vps4A-DN, enlarged intra-PV structures containing host endolysosomes accumulated, reflecting defects in PVM scission. Parasite mutants lacking T. gondii (Tg)GRA14 or TgGRA64, which interact with ESCRT, reduced CHMP4B-DN-induced PVM invaginations and intra-PV host organelles, with greater defects in a double knockout, revealing the exploitation of ESCRT to scavenge host organelles by Toxoplasma.

Precise partial root-zone irrigation technique and potassium-zinc fertigation management improve maize physio-biochemical responses, yield, and water use in arid climate.

BACKGROUND: To optimize irrigation water use and productivity, understanding the interactions between plants, irrigation techniques, and fertilization practices is crucial. Therefore, the experiment aims to assess the effectiveness of two application methods of potassium humate combined with chelated zinc under partial root-zone drip irrigation techniques on maize nutrient uptake, yield, and irrigation water use efficiency across two irrigation levels. METHODS: Open-field experiments were carried out in two summer seasons of 2021 and 2022 under alternate and fixed partial root-zone drip irrigation techniques to investigate their impacts at two irrigation levels and applied foliar and soil applications of potassium humate or chelated zinc in a sole and combinations on maize. RESULTS: Deficit irrigation significantly increased hydrogen peroxide levels and decreased proline, antioxidant enzymes, carbohydrate, chlorophyll (a + b), and nutrient uptake in both partial root-zone techniques. The implementation of combined soil application of potassium humate and chelated zinc under drought conditions on maize led to varying impacts on antioxidant enzymes and nutritional status, depending on the type of partial root-zone technique. Meanwhile, the results showed that fixed partial root-zone irrigation diminished the negative effects of drought stress by enhancing phosphorus uptake (53.8%), potassium uptake (59.2%), proline (74.4%) and catalase (75%); compared to the control. These enhancements may contribute to improving the defense system of maize plants in such conditions. On the other hand, the same previous treatments under alternate partial root zone modified the defense mechanism of plants and improved the contents of peroxidase, superoxide dismutase, and the uptake of magnesium, zinc, and iron by 81.3%, 82.3%, 85.1%, 56.9%, and 80.2%, respectively. CONCLUSIONS: Adopting 75% of the irrigation requirements and treating maize plants with the soil application of 3 g l-1 potassium humate combined with 1.25 kg ha-1 chelated zinc under alternate partial root-zone technique, resulted in the maximum root length, leaf water content, chlorophyll content, yield, and irrigation water use efficiency.

Inoculation with arbuscular mycorrhizal fungi improves plant biomass and nitrogen and phosphorus nutrients: a meta-analysis.

Arbuscular mycorrhizal fungi (AMF) have profound effects on plant growth and nitrogen (N) and phosphorus (P) nutrition. However, a comprehensive evaluation of how plant N and P respond to AMF inoculation is still unavailable. Here, we complied data from 187 original researches and carried out a meta-analysis to assess the effects of AMF inoculation on plant growth and N and P nutrition. We observe overall positive effects of AMF inoculation on plant performance. The mean increases of plant biomass, N concentration, P concentration, N and P uptake of whole plant are 47%, 16%, 27%, 67%, and 105%, respectively. AMF inoculation induces more increases in plant concentrations and storage of P than N. Plant responses to AMF inoculation are substantially higher with single AMF species than with mixed AMF species, in laboratory experiments than in field experiments, and in legumes than in non-legumes. The response ratios of plant N and P nutrition are positively correlated with AMF colonization rate, N addition, P addition, and water condition, while unvaried with experiment duration. The biggest and smallest effect sizes of AMF inoculation on plant performance are observed in the application of nitrate and ammonium, respectively. Accordingly, this meta-analysis study clearly suggests that AMF inoculation improves both plant N and P nutrients and systematically clarifies the variation patterns in AMF effects with various biotic and abiotic factors. These findings highlight the important role of AMF inoculation in enhancing plant N and P resource acquisitions and provide useful references for evaluating the AMF functions under the future global changes.

Intercropping enhances maize growth and nutrient uptake by driving the link between rhizosphere metabolites and microbiomes.

Intercropping leads to different plant roots directly influencing belowground processes and has gained interest for its promotion of increased crop yields and resource utilization. However, the precise mechanisms through which the interactions between rhizosphere metabolites and the microbiome contribute to plant production remain ambiguous, thus impeding the understanding of the yield-enhancing advantages of intercropping. This study conducted field experiments (initiated in 2013) and pot experiments, coupled with multi-omics analysis, to investigate plant-metabolite-microbiome interactions in the rhizosphere of maize. Field-based data revealed significant differences in metabolite and microbiome profiles between the rhizosphere soils of maize monoculture and intercropping. In particular, intercropping soils exhibited higher microbial diversity and metabolite chemodiversity. The chemodiversity and composition of rhizosphere metabolites were significantly related to the diversity, community composition, and network complexity of soil microbiomes, and this relationship further impacted plant nutrient uptake. Pot-based findings demonstrated that the exogenous application of a metabolic mixture comprising key components enriched by intercropping (soyasapogenol B, 6-hydroxynicotinic acid, lycorine, shikimic acid, and phosphocreatine) significantly enhanced root activity, nutrient content, and biomass of maize in natural soil, but not in sterilized soil. Overall, this study emphasized the significance of rhizosphere metabolite-microbe interactions in enhancing yields in intercropping systems. It can provide new insights into rhizosphere controls within intensive agroecosystems, aiming to enhance crop production and ecosystem services.

HY5: a key regulator for light-mediated nutrient uptake and utilization by plants.

ELONGATED HYPOCOTYL 5 (HY5), a bZIP-type transcription factor, is a master regulator of light-mediated responses. ELONGATED HYPOCOTYL 5 binds to the promoter of c. 3000 genes, thereby regulating various physiological and biological processes, including photomorphogenesis, flavonoid biosynthesis, root development, response to abiotic stress and nutrient homeostasis. In recent decades, it has become clear that light signaling plays a crucial role in promoting nutrient uptake and assimilation. Recent studies have revealed the molecular mechanisms underlying such encouraging effects and the crucial function of the transcription factor HY5, whose activity is regulated by many photoreceptors. The discovery that HY5 directly activates the expression of genes involved in nutrient uptake and utilization, including several nitrogen, iron, sulphur, phosphorus and copper uptake and assimilation-related genes, enhances our understanding of how light signaling regulates uptake and utilisation of multiple nutrients in plants. Here, we review recent advances in the role of HY5 in light-dependent nutrient uptake and utilization.

CEP hormones at the nexus of nutrient acquisition and allocation, root development, and plant-microbe interactions.

A growing understanding is emerging of the roles of peptide hormones in local and long-distance signalling that coordinates plant growth and development as well as responses to the environment. C-TERMINALLY ENCODED PEPTIDE (CEP) signalling triggered by its interaction with CEP RECEPTOR 1 (CEPR1) is known to play roles in systemic nitrogen (N) demand signalling, legume nodulation, and root system architecture. Recent research provides further insight into how CEP signalling operates, which involves diverse downstream targets and interactions with other hormone pathways. Additionally, there is emerging evidence of CEP signalling playing roles in N allocation, root responses to carbon levels, the uptake of other soil nutrients such as phosphorus and sulfur, root responses to arbuscular mycorrhizal fungi, plant immunity, and reproductive development. These findings suggest that CEP signalling more broadly coordinates growth across the whole plant in response to diverse environmental cues. Moreover, CEP signalling and function appear to be conserved in angiosperms. We review recent advances in CEP biology with a focus on soil nutrient uptake, root system architecture and organogenesis, and roles in plant-microbe interactions. Furthermore, we address knowledge gaps and future directions in this research field.

Determination of nutrient concentration in liquid culture of cyanobacteria Nostoc sp. by capillary electrophoresis and inductively coupled plasma mass spectrometry.

In this work, we demonstrate the use of capillary electrophoresis and inductively coupled plasma mass spectrometry, as competitive methods primarily for ion chromatography, to determine changes in the concentration of small inorganic ions in the Nostoc sp. culture medium. Although macronutrients were analyzed by capillary electrophoresis with conductivity detection, micronutrients were analyzed by inductively coupled plasma mass spectrometry. The different light settings (light intensity and spectral composition) had a visible effect on the culture growth and depletion of calcium, magnesium, and phosphate ions, and iron and manganese elements when comparing the behavior under red or violet light with that under blue light.

Impact of Irpex lenis and Schizophyllum commune endophytic fungi on Perilla frutescens: enhancing nutritional uptake, phytochemicals, and antioxidant potential.

BACKGROUND: Endophytic fungi (EF) reside within plants without causing harm and provide benefits such as enhancing nutrients and producing bioactive compounds, which improve the medicinal properties of host plants. Selecting plants with established medicinal properties for studying EF is important, as it allows a deeper understanding of their influence. Therefore, the study aimed to investigate the impact of EF after inoculating the medicinal plant Perilla frutescens, specifically focusing on their role in enhancing medicinal properties. RESULTS: In the current study, the impact of two EF i.e., Irpex lenis and Schizophyllum commune isolated from A. bracteosa was observed on plant Perilla frutescens leaves after inoculation. Plants were divided into four groups i.e., group A: the control group, group B: inoculated with I. lenis; group C: inoculated with S. commune and group D: inoculated with both the EF. Inoculation impact of I. lenis showed an increase in the concentration of chlorophyll a (5.32 mg/g), chlorophyll b (4.46 mg/g), total chlorophyll content (9.78 mg/g), protein (68.517 ± 0.77 mg/g), carbohydrates (137.886 ± 13.71 mg/g), and crude fiber (3.333 ± 0.37%). Furthermore, the plants inoculated with I. lenis showed the highest concentrations of P (14605 mg/kg), Mg (4964.320 mg/kg), Ca (27389.400 mg/kg), and Mn (86.883 mg/kg). The results of the phytochemical analysis also indicated an increased content of total flavonoids (2.347 mg/g), phenols (3.086 mg/g), tannins (3.902 mg/g), and alkaloids (1.037 mg/g) in the leaf extract of P. frutescens inoculated with I. lenis. Thus, overall the best results of inoculation were observed in Group B i.e. inoculated with I. lenis. GC-MS analysis of methanol leaf extract showed ten bioactive constituents, including 9-Octadecenoic acid (Z)-, methyl ester, and hexadecanoic acid, methyl ester as major constituents found in all the groups of P. frutescens leaves. The phenol (gallic acid) and flavonoids (rutin, kaempferol, and quercetin) were also observed to increase after inoculation by HPTLC analysis. The enhancement in the phytochemical content was co-related with improved anti-oxidant potential which was analyzed by DPPH (% Inhibition: 83.45 µg/ml) and FRAP (2.980 µM Fe (II) equivalent) assay as compared with the control group. CONCLUSION: Inoculation with I. lenis significantly enhances the uptake of nutritional constituents, phytochemicals, and antioxidant properties in P. frutescens, suggesting its potential to boost the therapeutic properties of host plants.

Synthesis of milk components involves different mammary metabolism adaptations in response to net energy and protein supplies in dairy cows.

Net energy for lactation (NEL) and metabolizable protein (MP) are the 2 main nutritional forces that drive synthesis of milk components. This study investigated mammary-gland metabolism in dairy cows in response to variations in the supply of NEL and MP. Four Holstein dairy cows were randomly assigned to a 4 × 4 Latin square design, in which each experimental period consisted of 14 d of dietary treatment. The diets provided 2 levels of NEL (low energy, 25.0 Mcal/d vs. high energy, 32.5 Mcal/d) and 2 levels of MP (low protein, 1,266 g/d vs. high protein, 2,254 g/d of protein digestible in the intestine) in a 2 × 2 factorial arrangement. Performance and dry matter intake (DMI) were measured during the last 5 d of each period, and the mammary net balance was measured on d 13 by collecting 6 sets of blood samples from the left carotid artery and left mammary vein. Mammary plasma flow was measured according to the Fick principle for Phe and Tyr. The mammary net balance of carbon equaled the uptake of nutrients expressed as carbon minus the output of lactose, fatty acids (FA) synthesized in the mammary gland, AA of milk protein, and glycerol-3P from triglyceride on d 13. Milk, lactose, fat, and protein yields increased when NEL and MP supplies increased. However, increasing the NEL supply increased FA synthesis more than increasing the protein supply did. In addition, FA secretion increased more than lactose secretion when the NEL supply increased. Increasing the NEL supply increased the left half-udder uptake of all major energy-yielding nutrients by increasing mammary plasma flow. However, nutrient uptake increased more than milk output did, which in turn increased carbon dioxide output. This increase in nutrient oxidation by the mammary gland decreased the mammary efficiency of nutrients utilization when the NEL supply increased. Increasing MP supply tended to increase glucose uptake through mammary clearance and increased mammary AA uptake with no change in mammary plasma flow. In addition, the protein supply did not change the mammary uptake of acetate or ß-hydroxybutyrate. The increase in milk-component secretions in response to either NEL or MP supplies occurred through different metabolic adaptations (increase in mammary plasma flow vs. clearances, respectively). These results suggest that the nutrient use by the mammary gland is highly flexible, which helps in maintaining milk and milk-component yields even with limiting nutrient supplies.

Novel epiphytic root-fungus symbiosis in the Indo-Pacific seagrass Thalassodendron ciliatum from the Red Sea.

Symbioses with fungi are important and ubiquitous on dry land but underexplored in the sea. As yet only one seagrass has been shown to form a specific root-fungus symbiosis that resembles those occurring in terrestrial plants, namely the dominant long-lived Mediterranean species Posidonia oceanica (Alismatales: Posidoniaceae) forming a dark septate (DS) endophytic association with the ascomycete Posidoniomyces atricolor (Pleosporales: Aigialaceae). Using stereomicroscopy, light and scanning electron microscopy, and DNA cloning, here we describe a novel root-fungus symbiosis in the Indo-Pacific seagrass Thalassodendron ciliatum (Alismatales: Cymodoceaceae) from a site in the Gulf of Aqaba in the Red Sea. Similarly to P. oceanica, the mycobiont of T. ciliatum occurs more frequently in thinner roots that engage in nutrient uptake from the seabed and forms extensive hyphal mantles composed of DS hyphae on the root surface. Contrary to P. oceanica, the mycobiont occurs on the roots with root hairs and does not colonize its host intraradically. While the cloning revealed a relatively rich spectrum of fungi, they were mostly parasites or saprobes of uncertain origin and the identity of the mycobiont thus remains unknown. Symbioses of seagrasses with fungi are probably more frequent than previously thought, but their functioning and significance are unknown. Melanin present in DS hyphae slows down their decomposition and so is true for the colonized roots. DS fungi may in this way conserve organic detritus in the seagrasses' rhizosphere, thus contributing to blue carbon sequestration in seagrass meadows.

Strategies for livestock wastewater treatment and optimised nutrient recovery using microalgal-based technologies.

Global sustainable development faces several challenges in addressing the needs of a growing population. Regarding food industries, the heightening pressure to meet these needs has resulted in increased waste generation. Thus, recognising these wastes as valuable resources is crucial to integrating sustainable models into current production systems. For instance, the current 24 billion tons of nutrient-rich livestock wastewater (LW) generated yearly could be recovered and valorised via biological uptake through microalgal biomass. Microalgae-based livestock wastewater treatment (MbLWT) has emerged as an effective technology for nutrient recovery, specifically targeting carbon, nitrogen, and phosphorus. However, the viability and efficacy of these systems rely on the characteristics of LW, including organic matter and ammonium concentration, content of suspended solids, and microbial load. Thus, this systematic literature review aims to provide guidance towards implementing an integral MbLWT system for nutrient control and recovery, discussing several pre-treatments used in literature to overcome the challenges regarding LW as a suitable media for microalgae cultivation.

Ensifer sp. GMS14 enhances soybean salt tolerance for potential application in saline soil reclamation.

Rhizosphere microbiomes play an important role in enhancing plant salt tolerance and are also commonly employed as bio-inoculants in soil remediation processes. Cultivated soybean (Glycine max) is one of the major oilseed crops with moderate salt tolerance. However, the response of rhizosphere microbes me to salt stress in soybean, as well as their potential application in saline soil reclamation, has been rarely reported. In this study, we first investigated the microbial communities of salt-treated and non-salt-treated soybean by 16S rRNA gene amplicon sequencing. Then, the potential mechanism of rhizosphere microbes in enhancing the salt tolerance of soybean was explored based on physiological analyses and transcriptomic sequencing. Our results suggested that Ensifer and Novosphingobium were biomarkers in salt-stressed soybean. One corresponding strain, Ensifer sp. GMS14, showed remarkable growth promoting characteristics. Pot experiments showed that GMS14 significantly improved the growth performance of soybean in saline soils. Strain GMS14 alleviated sodium ions (Na+) toxicity by maintaining low a Na+/K+ ratio and promoted nitrogen (N) and phosphorus (P) uptake by soybean in nutrient-deficient saline soils. Transcriptome analyses indicated that GMS14 improved plant salt tolerance mainly by ameliorating salt stress-mediated oxidative stress. Interestingly, GMS14 was evidenced to specifically suppress hydrogen peroxide (H2O2) production to maintain reactive oxygen species (ROS) homeostasis in plants under salt stress. Field experiments with GMS14 applications showed its great potential in saline soil reclamation, as evidenced by the increased biomass and nodulation capacity of GMS14-inoculated soybean. Overall, our findings provided valuable insights into the mechanisms underlying plant-microbes interactions, and highlighted the importance of microorganisms recruited by salt-stressed plant in the saline soil reclamation.

[Effect of combined application of organic and chemical fertilizers on yield and quality of Epimedium pubescens].

To investigate the effects of different ratios of organic and chemical fertilizers on the yield and quality of Epimedium pubescens,so as to provide a scientific basis for the fertilization of high-yield and high-quality E. pubescens cultivation. In this experiment,a field plot test was conducted,and CK(without fertilizer) was set as the control group,with five treatment groups with different ratios of organic fertilizers and chemical fertilizers set up,namely OF0(100% chemical fertilizers),OF25(25% organic fertilizers),OF50(50% organic fertilizers),OF75(75% organic fertilizers),and OF100(100% organic fertilizers). The effects of different fertilization patterns on the agronomic traits,yield,effective component content,nutrient accumulation,and soil physicochemical properties of E. pubescens were determined,and the yield and quality of the medicinal herb were comprehensively evaluated by using the CRITIC weights method. It was found that the herb yield of each treatment group was significantly increased compared with the CK group,although the yield of the groups with both organic fertilizer and chemical fertilizer was slightly lower than that of OF0. However,there was no significant difference,which indicated that the organic fertilizer combined with chemical fertilizer could ensure the herb yield. With the increase in organic fertilizer ratios,the medicinal components epimedin A,epimedin B,and epimedin C showed a tendency of first increasing and then decreasing,with the highest content in the OF25,while icariin showed a rising trend,with the best in the OF100. However,overall,the total flavonol glycosides ABCI accumulated the most in the OF25. The results of the CRITIC method showed that the top three fertilization treatments in terms of the comprehensive scores of the medicinal herb were OF25,OF50,and OF75. Organic fertilizer combined with chemical fertilizer is conducive to improving the soil's fertilizer holding and supply capacity,and the soil indexes are optimal in OF100. The soil enzyme activity is the highest in OF75. Meanwhile,organic fertilizer combined with chemical fertilizer can help the plant's uptake and accumulation of nutrients,and OF25 shows the most obvious effect.By comprehensively considering the influence of different ratios of organic and chemical fertilizers on the yield,effective component content,nutrient accumulation,and other indexes of E. pubescens,it is recommended that a 25% ratio(7 500 kg·hm~(-2)) of organic fertilizers and chemical fertilizers should be used in E. pubescens production in the first year,so as to promote the E. pubescens industry to increase yield and improve quality.

A Bioorthogonal Dual Fluorogenic Probe for the Live-Cell Monitoring of Nutrient Uptake by Mammalian Cells.

Cells rely heavily on the uptake of exogenous nutrients for survival, growth, and differentiation. Yet quantifying the uptake of small molecule nutrients at the single cell level is difficult. Here we present a new approach to studying the nutrient uptake in live single cells using Inverse Electron-Demand Diels Alder (IEDDA) chemistry. We have modified carboxyfluorescein-diacetate-succinimidyl esters (CFSE)-a quenched fluorophore that can covalently react with proteins and is only turned on in the cytosol of a cell following esterase activity-with a tetrazine. This tetrazine serves as a second quencher for the pendant fluorophore. Upon reaction with nutrients modified with an electron-rich or strained dienophile in an IEDDA reaction, this quenching group is destroyed, thereby enabling the probe to fluoresce. This has allowed us to monitor the uptake of a variety of dienophile-containing nutrients in live primary immune cell populations using flow cytometry and live-cell microscopy.

A systems-biology approach identifies co-expression modules in response to low phosphate supply in maize lines of different breeding history.

Plants cope with low phosphorus availability by adjusting growth and metabolism through transcriptomic and proteomic adaptations. We hypothesize that selected genotypes with distinct phosphorous (P) use efficiency covering the breeding history of European Flint heterotic pool provide a tool to reveal general and genotype-specific molecular responses to P limitation. We reconstructed protein and gene co-expression networks by weighted correlation network analysis and related these to phosphate deficiency-induced traits. In roots, low phosphate supply resulted in a decreasing abundance of proteins in the oxidative pentose phosphate pathway and a negative correlation with root and shoot phosphate content. We observed an increase in abundance and positive correlation with root and shoot phosphate content for proteins in sucrose biosynthesis, lipid metabolism, respiration and RNA processing. Purple acid phosphatases, superoxide dismutase and phenylalanine ammonia lyase were identified as being upregulated under low phosphate in all genotypes. Overall, correlations between protein and mRNA abundance changes were limited, with ribosomal proteins and the ubiquitin protein degradation pathway exclusively responding with protein abundance changes. Carbohydrate, phospho- and sulfo-lipid metabolism showed abundance changes at the protein and mRNA levels. These partially non-overlapping proteomic and transcriptomic adjustments to low phosphate suggest sugar and lipid metabolism as metabolic processes associated with improved P use efficiency specifically in Founder Flint lines. We identified a mitogen-activated protein kinase-kinase as a potential genotype-specific regulator of sucrose metabolism at low phosphate in Founder Flint line EP1. We conclude that, during breedingt of Elite Flint lines, regulation of primary metabolism has changed to result in a distinct low phosphate response in Founder lines.

Phosphorus storage and utilization strategies of two bloom-forming freshwater cyanobacteria.

The inter-relationships between cellular phosphorus (P) storage, dissolved inorganic P (DIP) uptake affinity, alkaline phosphatase activity (APA) and dissolved inorganic nitrogen (DIN) concentrations were studied in two ubiquitous diazotrophic freshwater cyanobacteria, Raphidiopsis raciborskii (six strains) and Chrysosporum ovalisporum (two strains). DIP uptake kinetics were measured using rates of incorporation of the radio-isotope, 33P and APA as a proxy for DOP-ester utilization. The study showed that DIP uptake of individual strains followed Michaelis-Menten kinetics (modified in our study to incorporate cellular P quotas), but differed with DIN and P availability, and between growth stages. High-affinity DIP uptake and APA were activated below a P quota threshold of approximately 0.01 µg P µg-1 C across the species and strains. C. ovalisporum had significantly higher APA and P quotas (per unit C and cell) but lower uptake affinity than R. raciborskii. Demand for DIP by C. ovalisporum increased when N fixation occurred, but typically not for R. raciborskii. Our results indicate that cyanobacterial species and strains differ in their strategies to P limiting conditions, and highlight the interplay between N and P. Physiological adaptations like APA and diazotrophy of cyanobacteria adapting to low DIP and/or DIN conditions may occur simultaneously and drive species dominance in oligotrophic environments.

Na+-dependent intestinal glucose absorption mechanisms and its luminal Na+ homeostasis across metamorphosis from tadpoles to frogs.

The abrupt morphological changes of the intestine during metamorphosis have been detailed in frogs. The features of intestinal metamorphosis are shortening of the intestine and remodeling of the intestinal epithelium. It is believed that the purpose of the morphological changes of the intestine is adaptation from aquatic herbivorous to carnivorous life. However, little is known about the physiological importance of these morphological changes. To elucidate the functional changes during metamorphosis, we measured luminal Na+ concentrations and Na+-dependent glucose uptake in tadpoles and adult African clawed frogs Xenopus laevis. The small intestine was isolated and divided into four segments in length, the luminal contents collected for analysis of ion concentration by ion chromatography. Phlorizin-sensitive glucose-induced short-circuit current (ΔIsc) was measured in intestinal preparations mounted in Ussing chambers. Although dietary sodium intake was extremely low in tadpoles, luminal Na+ concentration gradually increased along the proximal to the middle part of the intestine (>70 mM), and this Na+ concentration was comparable with that of carnivorous adult frogs. The increment of glucose-induced ΔIsc was observed in tadpole intestine. We also measured the ΔIsc induced by acetic acid, which is the major short-chain fatty acid produced by fermentation. The expression levels of mRNA for Na+-dependent glucose transporter 1 and tight junction protein claudin-15 in each intestinal segment was measured. These results suggest that luminal Na+ homeostasis is important and luminal Na+ is kept at a high concentration for Na+-dependent nutrient absorption mechanisms.

Complementary belowground strategies underlie species coexistence in an early successional forest.

Unravelling belowground strategies is critical for understanding species coexistence and successional dynamics; yet, our knowledge of nutrient acquisition strategies of forest species at different successional stages remains limited. We measured morphological (diameter, specific root length, and root tissue density), architectural (branching ratio), physiological (ammonium, nitrate, and glycine uptake rates) root traits, and mycorrhizal colonisation rates of eight coexisting woody species in an early successional plantation forest in subtropical China. By incorporating physiological uptake efficiency, we revealed a bi-dimensional root economics space comprising of an 'amount-efficiency' dimension represented by morphological and physiological traits, and a 'self-symbiosis' dimension dominated by architectural and mycorrhizal traits. The early pioneer species relied on root-fungal symbiosis, developing densely branched roots with high mycorrhizal colonisation rates for foraging mobile soil nitrate. The late pioneer species invested in roots themselves and allocated effort towards improving uptake efficiency of less-mobile ammonium. Within the root economics space, the covariation of axes with soil phosphorus availability also distinguished the strategy preference of the two successional groups. These results demonstrate the importance of incorporating physiological uptake efficiency into root economics space, and reveal a trade-off between expanding soil physical space exploration and improving physiological uptake efficiency for successional species coexistence in forests.

The function of the Medicago truncatula ZIP transporter MtZIP14 is linked to arbuscular mycorrhizal fungal colonization.

Soil micronutrient availability, including zinc (Zn), is a limiting factor for crop yield. Arbuscular mycorrhizal (AM) fungi can improve host plant growth and nutrition through the mycorrhizal pathway of nutrient uptake. Although the physiology of Zn uptake through the mycorrhizal pathway is well established, the identity of the related molecular components are unknown. Here, RNA-seq analysis was used to identify genes differentially-regulated by AM colonization and soil Zn concentration in roots of Medicago truncatula. The putative Zn transporter gene MtZIP14 was markedly up-regulated in M. truncatula roots when colonized by Rhizophagus irregularis. MtZIP14 restored yeast growth under low Zn availability. Loss-of-function mutant plants (mtzip14) had reduced shoot biomass compared to the wild-type when colonized by AM fungi and grown under low and sufficient soil Zn concentration; at high soil Zn concentration, there were no genotypic differences in shoot biomass. The vesicular and arbuscular colonization of roots was lower in the mtzip14 plants regardless of soil Zn concentration. We propose that MtZIP14 is linked to AM colonization in M. truncatula plants, with the possibility that MtZIP14 function with AM colonization is linked to plant Zn nutrition.

Phosphate starvation: response mechanisms and solutions.

Phosphorus is essential to plant growth and agricultural crop yields, yet the challenges associated with phosphorus fertilization in agriculture, such as aquatic runoff pollution and poor phosphorus bioavailability, are increasingly difficult to manage. Comprehensively understanding the dynamics of phosphorus uptake and signaling mechanisms will inform the development of strategies to address these issues. This review describes regulatory mechanisms used by specific tissues in the root apical meristem to sense and take up phosphate from the rhizosphere. The major regulatory mechanisms and related hormone crosstalk underpinning phosphate starvation responses, cellular phosphate homeostasis, and plant adaptations to phosphate starvation are also discussed, along with an overview of the major mechanism of plant systemic phosphate starvation responses. Finally, this review discusses recent promising genetic engineering strategies for improving crop phosphorus use and computational approaches that may help further design strategies for improved plant phosphate acquisition. The mechanisms and approaches presented include a wide variety of species including not only Arabidopsis but also crop species such as Oryza sativa (rice), Glycine max (soybean), and Triticum aestivum (wheat) to address both general and species-specific mechanisms and strategies. The aspects of phosphorus deficiency responses and recently employed strategies of improving phosphate acquisition that are detailed in this review may provide insights into the mechanisms or phenotypes that may be targeted in efforts to improve crop phosphorus content and plant growth in low phosphorus soils.