Nutrient Homeostasis Research Articles

Ectopic expression of the GRAS-type transcriptional regulator NSP2 in Parasponia triggers contrasting effects on symbioses.

Plants strictly control root endosymbioses with nutrient-scavenging arbuscular endomycorrhizal fungi or nodule inducing diazotrophic bacteria. The GRAS-type transcriptional regulator NODULATION SIGNALING PATHWAY 2 (NSP2) is a conserved hub in this process. The NSP2-regulated transcriptional network is instrumental in balancing nutrient homeostasis with symbiotic interactions. NSP2 activity is modulated post-transcriptionally by a specific microRNA. Overriding this control mechanism by ectopic expression of a miRNA-resistant NSP2 transgene enhances the symbiotic permissiveness to arbuscular endomycorrhizal fungi. Such engineered plants may possess enhanced capacities for nutrient uptake. However, the trade-off of this strategy on plant development or other symbiotic interactions, like nodulation, is yet to be fully understood. We used the nodulating Cannabaceae species Parasponia andersonii as an experimental system to study the effect of ectopic NSP2 expression. Parasponia and legumes (Fabaceae) diverged 100 million years ago, providing a unique comparative system to dissect the nodulation trait. Six independent transgenic Parasponia lines were generated that differed in the level of NSP2 expression in the root from 6 to 95-fold higher when compared to the empty vector control plants. Analysis of these plants revealed a positive correlation between mycorrhization and the NSP2 expression level, as well as with the expression of the symbiosis transcription factor CYCLOPS and the rate-limiting enzyme in the carotenoid biosynthetic pathway PHYTOENE SYNTHASE1 (PSY1). Yet ectopic expression of NSP2 affected plant architecture and root nodule organogenesis. This indicates a significant trade-off when leveraging NSP2 over-expression to enhance endomycorrhization.

Notch signaling pathway suppresses mRNA expression of hexokinase 2 under nutrient-poor conditions in U87-MG glioma cells.

Control of nutrient homeostasis plays a central role in cell proliferation/survival during embryonic development and tumor growth. Activation of the Notch signaling pathway, a major contributor to cell-cell interactions, is a potential mechanism for cell adaptation to nutrient-poor conditions. Our previous study also demonstrated that during embryogenesis when nutrients such as glutamine and growth factors are potentially maintained at lower levels, Notch signaling suppresses mRNA expression of hexokinase 2 (hk2), which is a glycolysis-associated gene, in the central nervous system. However, whether and how the genetic regulation of HK2 via Notch signaling contributes to cellular adaptability to nutrient-poor environments remains unknown. In this study, we performed gene expression analysis using a U87-MG human glioma cell line and revealed that under conditions where both glutamine and serum were absent, Notch signaling was activated and HK2 expression was downregulated by Notch signaling. We also found that Notch-mediated HK2 suppression was triggered in a Notch ligand-selective manner. Furthermore, HK2 was shown to inhibit cell proliferation of U87-MG gliomas, which might depend on Notch signaling activity. Together, our findings suggest the involvement of Notch-mediated HK2 suppression in an adaptive mechanism of U87-MG glioma cells to nutrient-poor conditions.

Failure of metabolic checkpoint control during late-stage granulopoiesis drives neutropenia in reticular dysgenesis

AbstractCellular metabolism is highly dynamic during hematopoiesis, yet the regulatory networks that maintain metabolic homeostasis during differentiation are incompletely understood. Herein, we have studied the grave immunodeficiency syndrome reticular dysgenesis caused by loss of mitochondrial adenylate kinase 2 (AK2) function. By coupling single-cell transcriptomics in samples from patients with reticular dysgenesis with a CRISPR model of this disorder in primary human hematopoietic stem cells, we found that the consequences of AK2 deficiency for the hematopoietic system are contingent on the effective engagement of metabolic checkpoints. In hematopoietic stem and progenitor cells, including early granulocyte precursors, AK2 deficiency reduced mechanistic target of rapamycin (mTOR) signaling and anabolic pathway activation. This conserved nutrient homeostasis and maintained cell survival and proliferation. In contrast, during late-stage granulopoiesis, metabolic checkpoints were ineffective, leading to a paradoxical upregulation of mTOR activity and energy-consuming anabolic pathways such as ribonucleoprotein synthesis in AK2-deficient cells. This caused nucleotide imbalance, including highly elevated adenosine monophosphate and inosine monophosphate levels, the depletion of essential substrates such as NAD+ and aspartate, and ultimately resulted in proliferation arrest and demise of the granulocyte lineage. Our findings suggest that even severe metabolic defects can be tolerated with the help of metabolic checkpoints but that the failure of such checkpoints in differentiated cells results in a catastrophic loss of homeostasis.

Heavy metal tolerance in crop plants: an in silico comprehensive analysis of Metal- tolerance gene family in barley

Heavy metal contamination in soil is a global concern due to its harmful effect to all living organisms. Phytoremediation is an emerging cost- effective technology, which utilizes different types of hyperaccumulator plants for the removal of heavy metal pollutants. Crop plants have been suggested as a good candidate for recultivation of agricultural soil in phytoremediation process, however the molecular mechanisms responsible for the crop tolerance to heavy metals is still unknown. Metal-tolerance proteins (MTPs) are divalent cation transporters that play critical roles in metal tolerance and ion homeostasis in plants. The current study identified 12 HvMTPs in the barley (Hordeum vulgare, Hv) genome; the majority of MTPs were hydrophobic proteins found in the vacuolar membrane. Gene expression profiling suggests that HvMTPs play an active role in maintaining barley nutrient homeostasis throughout its life cycle. The expression of barley HvMTP genes in the presence of heavy metals revealed that these MTPs were induced by at least one metal ion, implying their involvement in metal tolerance.

Autophagy-lysosomal-associated neuronal death in neurodegenerative disease.

Autophagy, the major lysosomal pathway for degrading damaged or obsolete constituents, protects neurons by eliminating toxic organelles and peptides, restoring nutrient and energy homeostasis, and inhibiting apoptosis. These functions are especially vital in neurons, which are postmitotic and must survive for many decades while confronting mounting challenges of cell aging. Autophagy failure, especially related to the declining lysosomal ("phagy") functions, heightens the neuron's vulnerability to genetic and environmental factors underlying Alzheimer's disease (AD) and other late-age onset neurodegenerative diseases. Components of the global autophagy-lysosomal pathway and the closely integrated endolysosomal system are increasingly implicated as primary targets of these disorders. In AD, an imbalance between heightened autophagy induction and diminished lysosomal function in highly vulnerable pyramidal neuron populations yields an intracellular lysosomal build-up of undegraded substrates, including APP-βCTF, an inhibitor of lysosomal acidification, and membrane-damaging Aβ peptide. In the most compromised of these neurons, β-amyloid accumulates intraneuronally in plaque-like aggregates that become extracellular senile plaques when these neurons die, reflecting an "inside-out" origin of amyloid plaques seen in human AD brain and in mouse models of AD pathology. In this review, the author describes the importance of lysosomal-dependent neuronal cell death in AD associated with uniquely extreme autophagy pathology (PANTHOS) which is described as triggered by lysosomal membrane permeability during the earliest "intraneuronal" stage of AD. Effectors of other cell death cascades, notably calcium-activated calpains and protein kinases, contribute to lysosomal injury that induces leakage of cathepsins and activation of additional death cascades. Subsequent events in AD, such as microglial invasion and neuroinflammation, induce further cytotoxicity. In major neurodegenerative disease models, neuronal death and ensuing neuropathologies are substantially remediable by reversing underlying primary lysosomal deficits, thus implicating lysosomal failure and autophagy dysfunction as primary triggers of lysosomal-dependent cell death and AD pathogenesis and as promising therapeutic targets.

Brassinosteroid improves resistance to phosphorus deficiency stress through regulating nutrient balance and reactive oxygen species scavenging in potato

Brassinosteroid (BR) plays a crucial role in plant growth, development and response to abiotic stress. However, the mechanism by which BR regulates the response of potato plants to phosphorus deficiency stress is still largely unknown. In this work, the effects of BR on the growth of potato plants under phosphorus deficient condition were investigated. Exogenous BR application mitigated the growth inhibition caused by phosphorus deficiency stress. Transcriptomic analyses revealed that BR application altered the expression of genes involved in mitogen-activated protein kinase (MAPK) signaling pathway, plant hormone signal transduction, and nitrogen and phosphorus metabolisms under phosphorus deficient condition. Further gene ontology (GO) analysis indicated a significant enrichment of genes associated with reactive oxygen species scavenging process. Ectopic expression of potato brassinosteroid synthesis gene StCYP85A1 in Arabidopsis improved the resistance of transgenic plants to phosphorus deficiency stress, as indicated by the increased germination greening ratio and root growth. Quantitative real time PCR and antioxidant enzyme activity analysis revealed that ectopic expression of StCYP85A1 altered the expression of genes related to nitrogen and phosphorus metabolism, and promoted antioxidant enzyme activity in transgenic plants. These findings indicated that BR improved the tolerance of potato plants to phosphorus deficiency stress by regulating nutrient homeostasis and reactive oxygen species scavenging.

Rapid Vacuolar Sorting of the Borate Transporter BOR1 Requires the Adaptor Protein Complex AP-4 in Arabidopsis.

Plants maintain nutrient homeostasis by controlling the activities and abundance of nutrient transporters. In Arabidopsis thaliana, the borate (B) transporter BOR1 plays a role in the efficient translocation of B under low-B conditions. BOR1 undergoes polyubiquitination in the presence of sufficient B and is then transported to the vacuole via multivesicular bodies (MVBs) to prevent B accumulation in tissues at a toxic level. A previous study indicated that BOR1 physically interacts with µ subunits of adaptor protein complexes AP-3 and AP-4, both involved in vacuolar sorting pathways. In this study, we investigated the roles of AP-3 and AP-4 subunits in BOR1 trafficking in Arabidopsis. The lack of AP-3 subunits did not affect either vacuolar sorting or polar localization of BOR1-GFP, whereas the absence of AP-4 subunits resulted in a delay in high-B-induced vacuolar sorting without affecting polar localization. Super-resolution microscopy revealed a rapid sorting of BOR1-GFP into AP-4-positive spots in the trans-Golgi network (TGN) upon high-B supply. These results indicate that AP-4 is involved in sequestration of ubiquitinated BOR1 into a TGN-specific subdomain "vacuolar-trafficking zone," and is required for efficient sorting to MVB and vacuole. Our findings elucidate the rapid vacuolar sorting process facilitated by AP-4 in plant nutrient transporters.

Zinc Seed Priming Alleviates Salinity Stress and Enhances Sorghum Growth by Regulating Antioxidant Activities, Nutrient Homeostasis, and Osmolyte Synthesis

Salinity is a serious abiotic stress that limits crop production and food security. Micronutrient application has shown promising results in mitigating the toxic impacts of salinity. This study assessed the impacts of zinc seed priming (ZSP) on the germination, growth, physiological and biochemical functioning of sorghum cultivars. The study comprised sorghum cultivars (JS-2002 and JS-263), salinity stress (control (0 mM) and 120 mM)), and control and ZSP (4 mM). Salinity stress reduced germination and seedling growth by increasing electrolyte leakage (EL: 60.65%), hydrogen peroxide (H2O2: 109.50%), malondialdehyde (MDA; 115.30%), sodium (Na), and chloride (Cl) accumulation and decreasing chlorophyll synthesis, relative water contents (RWC), total soluble proteins (TSPs), and potassium (K) uptake and accumulation. Nonetheless, ZSP mitigated the deleterious impacts of salinity and led to faster germination and better seedling growth. Zinc seed priming improved the chlorophyll synthesis, leaf water contents, antioxidant activities (ascorbate peroxide: APX, catalase: CAT, peroxidase: POD, superoxide dismutase: SOD), TSPs, proline, K uptake and accumulation, and reduced EL, MDA, and H2O2 production, as well as the accumulation of toxic ions (Na and Cl), thereby promoting better germination and growth. Thus, these findings suggested that ZSP can mitigate the toxicity of salinity by favoring nutrient homeostasis, antioxidant activities, chlorophyll synthesis, osmolyte accumulation, and maintaining leaf water status.

Silicon: A Powerful Aid for Medicinal and Aromatic Plants against Abiotic and Biotic Stresses for Sustainable Agriculture

Silicon plays a crucial role in enhancing plant tolerance to various abiotic and biotic stresses, including drought, salinity, heavy metals, and pathogen/pest attacks. Its application has shown promising results in improving stress tolerance and productivity in medicinal plants. This review synthesizes findings from numerous studies investigating the mechanisms by which silicon confers stress tolerance, including the regulation of antioxidant systems, water relations, nutrient homeostasis, phytohormone signaling, and stress-responsive gene expression. Additionally, it examines the effects of silicon supplementation on the production of valuable secondary metabolites and essential oils in medicinal plants. Silicon application can significantly mitigate stress-induced damage in plants, including medicinally important species such as borage, honeysuckle, licorice, Damask rose, savory, basil, and eucalyptus. The deposition of silicon in cell walls provides physical reinforcement and acts as a barrier against pathogen invasion and insect herbivory. Furthermore, silicon fertilization can enhance the production of valuable secondary metabolites in medicinal crops under stress conditions. The findings underscore the potential of silicon fertilization as a sustainable strategy for improving the productivity and quality of medicinal crops under changing environmental conditions, highlighting the need for further research to elucidate the molecular mechanisms underlying silicon-mediated stress tolerance and practical applications in medicinal plant cultivation.

Enhancing drought-salinity stress tolerance in lettuce: Synergistic effects of salicylic acid and melatonin

Salicylic acid (SA) and melatonin (MEL) are affordable and effective phytohormones that help mitigate environmental stress. However, the combined benefits of SA and MEL in managing salt and drought stress in lettuce have not been evaluated. Therefore, this study was designed to evaluate the effectiveness of foliar spraying with 1.0 mM SA and 100 µM MEL, either alone or in combination, to enhance lettuce yield, growth, photosynthetic pigments, mineral status, quality, and antioxidant response under four different irrigation regimes. The irrigation practices used were: full irrigation (FI, irrigated with 0.18 dS m−1 at 100 % field capacity [FC]), deficit irrigation (DI, irrigated with 0.18 dS m−1 at 75 % FC), saline irrigation (SW, irrigated with 2.5 dS m−1 at 100 % FC), and deficit saline irrigation (DSW, irrigated with 2.5 dS m−1 at 75 % FC). Additionally, a control treatment (CK) was carried out with foliar application of distilled water and irrigation at 0.18 dS m−1. Compared to the CK, the application of SA, MEL, and SA+MEL increased evapotranspiration by 4.3 %, 8.6 %, and 15.1 %, and yield by 10.2 %, 16.4 %, and 23.8 %, respectively, under FI conditions. Furthermore, the joint application of SA and MEL at FI showed 25.3 % and 20.2 % higher K+/Na+ and Ca2+/Na+ ratios, respectively, compared to the CK. Additionally, the co-application of SA+MEL improved chlorophyll a, b, and carotenoid levels by 19.2 %, 17.2 %, and 20.4 %, respectively, under FI conditions, compared to the CK. Exogenous application of SA, MEL, and SA+MEL also improved total soluble solids by 17.3 %, 18.5 %, and 11.1 % and reduced nitrate content by 9.7 %, 10.4 %, and 13.5 % in lettuce under FI conditions, compared to the CK. The application of SA+MEL together resulted in a more pronounced increase in vitamin C content compared to supplying SA and MEL individually. Moreover, under DSW conditions, exogenous application of SA, MEL, and SA+MEL decreased the membrane stability index by 13.7 %, 9.4 %, and 6.3 %, increased malondialdehyde by 65.4 %, 40.8 %, and 36.6 %, and increased proline content by 68.4 %, 65.4 %, and 96.4 %, respectively, compared to the CK. Moreover, exogenous SA+MEL significantly increased the activities of superoxide dismutase, catalase, peroxidase enzymes under both SW and DSW conditions compared to the SA or MEL. Conversely, the activity of ascorbate peroxidase enzyme showed a gradual decrease in DI, SW, and DSW conditions, relative to the FI conditions. In conclusion, the integrated application of SA+MEL is an optimal strategy to enhance yield, morpho-physiological traits, nutrient homeostasis, antioxidant capacity, and quality in lettuce and mitigate the adverse effects of drought, salinity, and drought-salinity stress.

Erythropoietin enhances iron bioavailability in HepG2 cells by downregulating hepcidin through mTOR, C/EBPα and HIF-1α

The regulation of iron (Fe) levels is essential to maintain an adequate supply for erythropoiesis, among other processes, and to avoid possible toxicity. The liver-produced peptide hepcidin is regarded as the main regulator of Fe absorption in enterocytes and release from hepatocytes and macrophages, as it impairs Fe export through ferroportin. The glycoprotein erythropoietin (Epo) drives erythroid progenitor survival and differentiation in the bone marrow, and has been linked to the mobilization of Fe reserves necessary for hemoglobin production. Herein we show that Epo inhibits hepcidin expression directly in the HepG2 hepatic cell line, thus leading to a decrease in intracellular Fe levels. Such inhibition was dependent on the Epo receptor-associated kinase JAK2, as well as on the PI3K/AKT/mTOR pathway, which regulates nutrient homeostasis. Epo was also found to decrease binding of the C/EBP-α transcription factor to the hepcidin promoter, which could be attributed to an increased expression of its inhibitor CHOP. Epo did not only hinder the stimulating effect of C/EBP-α on hepcidin transcription, but also favored hepcidin inhibition by HIF-1α, by increasing is nuclear translocation as well as its protein levels. Moreover, in assays with the inhibitor genistein, this transcription factor was found necessary for Epo-induced hepcidin suppression. Our findings support the involvement of the PI3K/AKT/mTOR pathway in the regulation of Fe levels by Epo, and highlight the contrasting roles of the C/EBP-α and HIF-1α transcription factors as downstream effectors of the cytokine in this process.

A correlation of serum fibroblast growth factor 21 level with inflammatory markers and indicators of nutritional status in patients with inflammatory bowel disease.

Fibroblast growth factor 21 (FGF21) is a stress-inducible hormone that regulates nutrient and metabolic homeostasis. Inflammatory state is one of the stimulators of FGF21 secretion. The aim of the study was to assess correlations between serum FGF21 level and inflammatory markers as well as nutritional status indicators in patients with inflammatory bowel disease (IBD). Fasting serum FGF21 level was measured using ELISA test in 105 IBD patients and 17 healthy controls. There were 31 subjects with active ulcerative colitis (UC), 16 with inactive UC, 36 with active Crohn's disease (CD), and 22 with inactive CD. Clinical and endoscopic activity of IBD was evaluated based on validated scales and indices. Fecal calprotectin, serum CRP, and selected parameters of nutritional status were tested in all patients. Serum FGF21 level was characterized by fluctuations depending on the IBD activity. FGF21 level was significantly higher in both active UC and CD compared to inactive phases of the diseases and to the controls. A correlation between FGF21 and fecal calprotectin levels was also found in UC and CD. Additionally, in CD, FGF21 level positively correlated with CRP level. In both UC and CD, a negative correlation was noted between FGF21 level and nutritional status parameters including cholesterol, protein, albumin levels, and BMI. The intensity of intestinal inflammation is related to FGF21 level, which correlates negatively with nutritional status indicators in IBD. The disturbances in FGF21 secretion may contribute to the multifactorial pathogenesis of malnutrition and weight loss in IBD patients.

MFPINC: prediction of plant ncRNAs based on multi-source feature fusion

Non-coding RNAs (ncRNAs) are recognized as pivotal players in the regulation of essential physiological processes such as nutrient homeostasis, development, and stress responses in plants. Common methods for predicting ncRNAs are susceptible to significant effects of experimental conditions and computational methods, resulting in the need for significant investment of time and resources. Therefore, we constructed an ncRNA predictor(MFPINC), to predict potential ncRNA in plants which is based on the PINC tool proposed by our previous studies. Specifically, sequence features were carefully refined using variance thresholding and F-test methods, while deep features were extracted and feature fusion were performed by applying the GRU model. The comprehensive evaluation of multiple standard datasets shows that MFPINC not only achieves more comprehensive and accurate identification of gene sequences, but also significantly improves the expressive and generalization performance of the model, and MFPINC significantly outperforms the existing competing methods in ncRNA identification. In addition, it is worth mentioning that our tool can also be found on Github (https://github.com/Zhenj-Nie/MFPINC) the data and source code can also be downloaded for free.

Multifaceted Ability of Organic Fertilizers to Improve Crop Productivity and Abiotic Stress Tolerance: Review and Perspectives

The long-term use of chemical fertilizers poses a serious threat to crop productivity and soil quality. Organic fertilizers are used to improve the soil fertility and crop productivity. The application of organic fertilizers improves soil health and plant growth by improving the soil organic matter (SOM), soil structure, aggregate stability, nutrient uptake, water-holding capacity, cation exchange capacity, nutrient use efficiency and microbial activities of soil. The intensity of abiotic stress is continuously increasing, which is a serious threat to crop productivity and global food security. However, organic fertilizers have been reported to improve tolerance against drought, salinity, heat and heavy metal (HM) stresses. The application of organic fertilizer improves the leaf water status, nutrient uptake, nutrient homeostasis, synthesis of chlorophyll, osmolytes, hormones, secondary metabolites, antioxidant activities and gene expression, resulting in improved tolerance against drought, salinity, heat, and heavy metals. In the present review, we have discussed the ability of organic fertilizers to improve soil fertility, crop yield, and the nutrient use efficiency. We have also presented the various mechanisms through which organic fertilizers improve tolerance against drought, salinity, heat, and heavy metals. Therefore, this review will put forth new directions for researchers working on the use of organic materials to improve soil fertility, crop productivity and tolerance against abiotic stresses.

The NDR family of kinases: essential regulators of aging.

Aging is defined as a progressive decline of cognitive and physiological functions over lifetime. Since the definition of the nine hallmarks of aging in 2013 by López-Otin, numerous studies have attempted to identify the main regulators and contributors in the aging process. One interesting group of proteins whose participation has been implicated in several aging hallmarks are the nuclear DBF2-related (NDR) family of serine-threonine AGC kinases. They are one of the core components of the Hippo signaling pathway and include NDR1, NDR2, LATS1 and LATS2 in mammals, along with its highly conserved metazoan orthologs; Trc in Drosophila melanogaster, SAX-1 in Caenorhabditis elegans, CBK1, DBF20 in Saccharomyces cerevisiae and orb6 in Saccharomyces pombe. These kinases have been independently linked to the regulation of widely diverse cellular processes disrupted during aging such as the cell cycle progression, transcription, intercellular communication, nutrient homeostasis, autophagy, apoptosis, and stem cell differentiation. However, a comprehensive overview of the state-of-the-art knowledge regarding the post-translational modifications of and by NDR kinases in aging has not been conducted. In this review, we summarize the current understanding of the NDR family of kinases, focusing on their relevance to various aging hallmarks, and emphasize the growing body of evidence that suggests NDR kinases are essential regulators of aging across species.

A rapid and simple non-radioactive assay for measuring uptake by solute carrier transporters.

Introduction: Solute carrier (SLC) transport proteins play a crucial role in maintaining cellular nutrient and metabolite homeostasis and are implicated in various human diseases, making them potential targets for therapeutic interventions. However, the study of SLCs has been limited due to the lack of suitable tools, particularly cell-based substrate uptake assays, necessary for understanding their biological functions and for drug discovery purposes. Methods: In this study, a cell-based uptake assay was developed using a stable isotope-labeled compound as the substrate for SLCs, with detection facilitated by liquid chromatography-tandem mass spectrometry (LC-MS/MS). This assay aimed to address the limitations of existing assays, such as reliance on hazardous radiolabeled substrates and limited availability of fluorescent biosensors. Results: The developed assay was successfully applied to detect substrate uptakes by two specific SLCs: L-type amino acid transporter 1 (LAT1) and sodium taurocholate co-transporting polypeptide (NTCP). Importantly, the assay demonstrated comparable results to the radioactive method, indicating its reliability and accuracy. Furthermore, the assay was utilized to screen for novel inhibitors of NTCP, leading to the identification of a potential NTCP inhibitor compound. Discussion: The findings highlight the utility of the developed cell-based uptake assay as a rapid, simple, and environmentally friendly tool for investigating SLCs' biological roles and for drug discovery purposes. This assay offers a safer alternative to traditional methods and has the potential to contribute significantly to advancing our understanding of SLC function and identifying therapeutic agents targeting SLC-mediated pathways.

Overexpression of SQUAMOSA promoter binding protein-like 4a (NtSPL4a) alleviates Cd toxicity in Nicotiana tabacum

Squamosa Promoter Binding Protein-Like (SPL) plays a crucial role in regulating plant development and combating stress, yet its mechanism in regulating resistance to Cd toxicity remains unclear. In this study, we cloned a nuclear-localized transcription factor, NtSPL4a, from the tobacco cultivar TN90. Transient co-expression results showed that miR156 significantly reduced the expression of NtSPL4a by binding to the 3′-UTR of its transcript. We obtained transgenic tobacco overexpressing NtSPL4a (including the 3′-UTR) and NtSPL4aΔ (lacking the 3′-UTR) through Agrobacterium-mediated genetic transformation. Compared to the wild type (WT), overexpression of NtSPL4a/NtSPL4aΔ shortened the flowering time and exhibited a more developed root system. The transgenic tobacco showed significantly reduced Cd content, being 85.1% (OE-NtSPL4a) and 46.7% (OE-NtSPL4aΔ) of WT, respectively. Moreover, the upregulation of NtSPL4a affected the mineral nutrient homeostasis in transgenic tobacco. Additionally, overexpression of NtSPL4a/NtSPL4aΔ effectively alleviated leaf chlorosis and oxidative stress induced by Cd toxicity. One possible reason is that the overexpression of NtSPL4a/NtSPL4aΔ can effectively promote the accumulation of non-enzymatic antioxidants. A comparative transcriptomic analysis was performed between transgenic tobacco and WT to further unravel the global impacts brought by NtSPL4a. The tobacco overexpressing NtSPL4a had 183 differentially expressed genes (77 upregulated, 106 downregulated), while the tobacco overexpressing NtSPL4aΔ had 594 differentially expressed genes (244 upregulated, 350 downregulated) compared to WT. These differentially expressed genes mainly included transcription factors, metal transport proteins, flavonoid biosynthesis pathway genes, and plant stress-related genes. Our study provides new insights into the role of the transcript factor SPL in regulating Cd tolerance.

Microbiota metabolism of intestinal amino acids impacts host nutrient homeostasis and physiology

The intestine and liver are thought to metabolize dietary nutrients and regulate host nutrient homeostasis. Here, we find that the gut microbiota also reshapes the host amino acid (aa) landscape via efficiently metabolizing intestinal aa. To identify the responsible microbes/genes, we developed a metabolomics-based assay to screen 104 commensals and identified candidates that efficiently utilize aa. Using genetics, we identified multiple responsible metabolic genes in phylogenetically diverse microbes. By colonizing germ-free mice with the wild-type strain and their isogenic mutant deficient in individual aa-metabolizing genes, we found that these genes regulate the availability of gut and circulatory aa. Notably, microbiota genes for branched-chain amino acids (BCAAs) and tryptophan metabolism indirectly affect host glucose homeostasis via peripheral serotonin. Collectively, at single-gene level, this work characterizes a microbiota-encoded metabolic activity that affects host nutrient homeostasis and provides a roadmap to interrogate microbiota-dependent activity to improve human health.

Investigating aluminum toxicity effects on callose deposition, oxidative stress, and nutrient homeostasis in banana genotypes.

Aluminum (Al) toxicity poses a significant challenge to agricultural productivity, particularly in acidic soils. The banana crop, predominantly cultivated in tropical and subtropical climates, often grapples with low pH and Al toxicity. This study seeks to explore the differential responses of two banana genotypes with varying Al tolerance (Baodao and Baxi) to Al exposure (100 and 500 µM) for 24 h. Microscopic analysis uncovered distinctive structural modifications in root cells, with Baodao displaying more severe alterations in response to Al stress. There was higher superoxide (O2-.) and hydrogen peroxide (H2O2) production and lipid peroxidation in Baodao indicating enhanced oxidative stress and membrane damage. Al accumulation in root tips was higher in Baxi than Baodao, while the roots of Baodao had a higher accumulation of callose. Nutrient content analysis revealed alterations in ion levels, highlighting the impact of Al exposure on nutrient uptake and homeostasis. In summary, Al differentially affects callose deposition, which, in turn, leads to Al uptake and nutrient homeostasis alteration in two contrasting banana genotypes. This intricate interplay is a key factor in understanding plant responses to aluminum toxicity and can inform strategies for crop improvement and soil management in aluminum-stressed environments.

Comparison of two subspecies of a halophytic multi-use plant Mertensia maritima in vitro and ex vitro: propagation, salinity tolerance and mineral nutrition

The aim of the present study was to compare morphological and physiological responses to increasing salinity of the two subspecies of Mertensia maritima during in vitro propagation in two different systems, and subsequent ex vitro cultivation. Plants were brought into culture using seeds and further propagated on Murashige and Skoog medium supplemented with thidiazuron and naphthaleneacetic acid either on agar-solidified or liquid medium with a temporary immersion system (Plantform bioreactors). Salinity tolerance were tested both in tissue culture and with ex vitro greenhouse-cultivated plants. Low concentration of NaCl increased explant biomass in agar-solidified medium, with no negative consequences even at high concentration. However, the effect of salinity on liquid medium was genotype-specific. Explants in Plantform bioreactors showed several-fold higher biomass in comparison to that on agar-solidified medium, but the multiplication potential was not significantly affected. Ex vitro plants were negatively influenced by increasing NaCl concentration in substrate. In contrast to in vitro plants, accumulation potential of Na⁺ in ex vitro plants was low. One of adaptations to salinity at the whole plant level was maintenance of adequate tissue mineral nutrient homeostasis, as mineral nutrient concentrations were not negatively affected by increasing salinity.