Unlocking the potential of exosomes: a breakthrough in the theranosis of degenerative orthopaedic diseases.

Degenerative orthopaedic diseases pose a notable worldwide public health issue attributable to the global aging population. Conventional medical approaches, encompassing physical therapy, pharmaceutical interventions, and surgical methods, face obstacles in halting or reversing the degenerative process. In recent times, exosome-based therapy has gained widespread acceptance and popularity as an effective treatment for degenerative orthopaedic diseases. This therapeutic approach holds the potential for "cell-free" tissue regeneration. Exosomes, membranous vesicles resulting from the fusion of intracellular multivesicles with the cell membrane, are released into the extracellular matrix. Addressing challenges such as the rapid elimination of natural exosomes in vivo and the limitation of drug concentration can be effectively achieved through various strategies, including engineering modification, gene overexpression modification, and biomaterial binding. This review provides a concise overview of the source, classification, and preparation methods of exosomes, followed by an in-depth analysis of their functions and potential applications. Furthermore, the review explores various strategies for utilizing exosomes in the treatment of degenerative orthopaedic diseases, encompassing engineering modification, gene overexpression, and biomaterial binding. The primary objective is to provide a fresh viewpoint on the utilization of exosomes in addressing bone degenerative conditions and to support the practical application of exosomes in the theranosis of degenerative orthopaedic diseases.

Zooming in and Out of Programmed Cell Death in Osteoarthritis: A Scientometric and Visualized Analysis.

During the past decade, mounting evidence has increasingly linked programmed cell death (PCD) to the progression and development of osteoarthritis (OA). There is a significant need for a thorough scientometric analysis that recapitulates the relationship between PCD and OA. This study aimed to collect articles and reviews focusing on PCD in OA, extracting data from January 1st, 2013, to October 31st, 2023, using the Web of Science. Various tools, including VOSviewer, CiteSpace, Pajek, Scimago Graphica, and the R package, were employed for scientometric and visualization analyses. Notably, China, the USA, and South Korea emerged as major contributors, collectively responsible for more than 85% of published papers and significantly influencing research in this field. Among different institutions, Shanghai Jiao Tong University, Xi'an Jiao Tong University, and Zhejiang University exhibited the highest productivity. Prolific authors included Wang Wei, Wang Jing, and Zhang Li. Osteoarthritis and Cartilage had the most publications in this area. Keywords related to PCD in OA prominently highlighted 'chondrocytes', 'inflammation', and 'oxidative stress', recognized as pivotal mechanisms contributing to PCD within OA. This study presents the first comprehensive scientometric analysis, offering a broad perspective on the knowledge framework and evolving patterns concerning PCD in relation to OA over the last decade. Such insights can aid researchers in comprehensively understanding this field and provide valuable directions for future explorations.

Targeting ferroptosis unveils a new era for traditional Chinese medicine: a scientific metrology study.

In the past 11 years, there has been a surge in studies exploring the regulatory effect of Traditional Chinese Medicine (TCM) on ferroptosis. However, a significant gap persists in comprehensive scientometric analysis and scientific mapping research, especially in tracking the evolution, primary contributors, and emerging research focal points. This study aims to comprehensively update the advancements in targeting ferroptosis with various TCMs during the previous 11 years. The data, covering the period from 1 January 2012, to 30 November 2023, were retrieved from the Web of Science database. For in-depth scientometric and visualized analyses, a series of advanced analytical instruments were employed. The findings highlight China's predominant role, accounting for 71.99% of total publications and significantly shaping research in this domain. Noteworthy productivity was observed at various institutions, including Guangzhou University of Chinese Medicine, Chengdu University of Traditional Chinese Medicine, and Zhejiang University. Thomas Efferth emerged as the foremost author within this field, while Frontiers in Pharmacology boasted the highest publication count. This study pinpointed hepatocellular carcinoma, chemical and drug-induced liver injury, mitochondrial diseases, acute kidney injury, and liver failure as the most critical disorders addressed in this research realm. The research offers a comprehensive bibliometric evaluation, enhancing our understanding of the present status of TCM therapy in managing ferroptosis-related diseases. Consequently, it aids both seasoned researchers and newcomers by accelerating access to vital information and fostering innovative concept extraction within this specialized field.

A bibliometric and visualized analysis of nanoparticles in musculoskeletal diseases (from 2013 to 2023).

As the pace of research on nanomedicine for musculoskeletal (MSK) diseases accelerates, there remains a lack of comprehensive analysis regarding the development trajectory, primary authors, and research focal points in this domain. Additionally, there's a need of detailed elucidation of potential research hotspots. The study gathered articles and reviews focusing on the utilization of nanoparticles (NPs) for MSK diseases published between 2013 and 2023, extracted from the Web of Science database. Bibliometric and visualization analyses were conducted using various tools such as VOSviewer, CiteSpace, Pajek, Scimago Graphica, and the R package. China, the USA, and India emerged as the key drivers in this research domain. Among the numerous institutions involved, Shanghai Jiao Tong University, Chinese Academy of Sciences, and Sichuan University exhibited the highest productivity levels. Vallet-Regi Maria emerged as the most prolific author in this field. International Journal of Nanomedicine accounted for the largest number of publications in this area. The top five disorders of utmost significance in this field include osteosarcoma, cartilage diseases, bone fractures, bone neoplasms, and joint diseases. These findings are instrumental in providing researchers with a comprehensive understanding of this domain and offer valuable perspectives for future investigations.

Unraveling differential characteristics and mechanisms of nitrogen uptake in wheat cultivars with varied nitrogen use efficiency.

Nitrogen uptake is crucial to wheat nitrogen use efficiency (NUE). The study's findings indicate that both high- and low-NUE cultivars exhibited highest nitrogen uptake efficiency (NupE) under 0.2 mM nitrogen. Under 2 mM nitrogen, their NupEs decrease significantly, while uptakes to NO3- were notably higher than that of NH4+. Strikingly, high-NUE cultivars exhibited a significantly higher NH4+ uptake rate than low NUE cultivars, resulting in a marked improvement in their ability to take up nitrogen. The NUEs of the cultivars with 5 mM nitrogen were almost half that of 2 mM nitrogen. NO3- uptake primarily occurred in the mature zone of roots, while NH4+ uptake took place in the root tip meristem and elongation zones. Notably, the NH4+ uptake in root tip meristematic zone of high-NUE cultivar was significantly higher than that of low NUE cultivar. Furthermore, the NO3- uptake of high-NUE cultivar in the root mature zone was significantly higher than that of low-NUE cultivar under 2 mM nitrogen. These findings were consistent with the significantly higher expression levels of TaAMT in root tip and of TaNRT in root mature area of high-NUE cultivar compared to low-NUE cultivar, respectively, enabling efficient absorption of NO3- and NH4+ and transport of NO3- to shoot. The high-NUE cultivars showed elevated expression of amino acid transporters further promoting nitrogen uptake, and conversion of nitrogen into ureides and amino acids further facilitated inorganic nitrogen uptake by roots. The differential findings offer valuable insights into novel variety breeding of high NUE in the future.

Global research landscape on the crosstalk between ferroptosis and musculoskeletal diseases: A bibliometric and visualized analysis.

Over the past 11 years, mounting evidence has suggested a significant association between ferroptosis and the development and progression of musculoskeletal (MSK) diseases, such as osteoporosis and osteoarthritis. However, a comprehensive bibliometric analysis summarizing the relationship between ferroptosis and MSK diseases is currently lacking. The present study collected articles and reviews on the topic of ferroptosis in MSK diseases. The data were collected from January 1st, 2012 to June 30th, 2023 by screening the Web of Science database. Various tools, including VOSviewer, CiteSpace, Pajek, the R package, and others, were used to conduct bibliometric and visualization analyses. Notably, China, the USA, and Italy emerged as primary contributors, jointly accounting for over 80 % of published documents, thereby shaping research in this domain. Among the diverse institutions, Shanghai Jiao Tong University, Soochow University, and Huazhong University of Science and Technology displayed the highest productivity levels. The most prolific authors include Sun Kai, Shang Peng, and Jing Xingzhi. Oxidative Medicine and Cellular Longevity stood out with the largest number of publications in this area. The five most significant disorders in this field are bone fractures, osteosarcoma, bone neoplasms, joint diseases, and osteoporotic fractures. This study represents an inaugural comprehensive bibliometric analysis, presenting a holistic view of the knowledge framework and developmental patterns in ferroptosis concerning MSK diseases over the previous eleven years. This information can aid researchers in acquiring a thorough grasp of this domain and offer invaluable insights for forthcoming explorations.

Frictional Wear and Thermal Fatigue Properties of Die Steel after Ultrasound-Assisted Alloying.

The surface layer of 8407 die steel was strengthened using the combination of ultrasonic surface rolling and high-energy ion implanting in the present work. The strengthened layer was then characterized via microstructure observation, composition analysis, and hardness test. After that, the frictional wear and thermal fatigue properties of high-energy ion implanting specimens and composite-reinforced specimens were compared. Results show that the pretreatment of specimens with ultrasonic surface rolling causes grain refinement in the material surface, which promotes the strengthening effect of high-energy ion implanting. The wear volume of composite-reinforced specimens at medium and high frequencies is reduced by about 20%, and the wear resistance of these specimens is significantly improved with a lower friction coefficient and wear volume at moderate and high frequencies in alternating load friction experiments. Meanwhile, the thermal fatigue crack depth of composite-reinforced specimens is reduced by about 47.5%, which effectively prevents the growth of thermal cracks in the surface, thus improving the curing ability of the implanted elements. Therefore, composite strengthening of the mold steel surface is conducive to improving the cycle life, ensuring accuracy, effectively hindering the expansion of thermal cracks, and saving the cost of production.

Osteoarthritis: Role of Peroxisome Proliferator-Activated Receptors.

Osteoarthritis (OA) represents the foremost degenerative joint disease observed in a clinical context. The escalating issue of population aging significantly exacerbates the prevalence of OA, thereby imposing an immense annual economic burden on societies worldwide. The current therapeutic landscape falls short in offering reliable pharmaceutical interventions and efficient treatment methodologies to tackle this growing problem. However, the scientific community continues to dedicate significant efforts towards advancing OA treatment research. Contemporary studies have discovered that the progression of OA may be slowed through the strategic influence on peroxisome proliferator-activated receptors (PPARs). PPARs are ligand-activated receptors within the nuclear hormone receptor family. The three distinctive subtypes-PPARα, PPARß/δ, and PPARγ-find expression across a broad range of cellular terminals, thus managing a multitude of intracellular metabolic operations. The activation of PPARγ and PPARα has been shown to efficaciously modulate the NF-κB signaling pathway, AP-1, and other oxidative stress-responsive signaling conduits, leading to the inhibition of inflammatory responses. Furthermore, the activation of PPARγ and PPARα may confer protection to chondrocytes by exerting control over its autophagic behavior. In summation, both PPARγ and PPARα have emerged as promising potential targets for the development of effective OA treatments.

Crosstalk between ferroptosis and chondrocytes in osteoarthritis: a systematic review of in vivo and in vitro studies.

Purpose: Recent scientific reports have revealed a close association between ferroptosis and the occurrence and development of osteoarthritis (OA). Nevertheless, the precise mechanisms by which ferroptosis influences OA and how to hobble OA progression by inhibiting chondrocyte ferroptosis have not yet been fully elucidated. This study aims to conduct a comprehensive systematic review (SR) to address these gaps. Methods: Following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020, we conducted a comprehensive search of the Embase, Ovid, ProQuest, PubMed, Scopus, the Cochrane Library, and Web of Science databases to identify relevant studies that investigate the association between ferroptosis and chondrocytes in OA. Our search included studies published from the inception of these databases until January 31st, 2023. Only studies that met the predetermined quality criteria were included in this SR. Results: In this comprehensive SR, a total of 21 studies that met the specified criteria were considered suitable and included in the current updated synthesis. The mechanisms underlying chondrocyte ferroptosis and its association with OA progression involve various biological phenomena, including mitochondrial dysfunction, dysregulated iron metabolism, oxidative stress, and crucial signaling pathways. Conclusion: Ferroptosis in chondrocytes has opened an entirely new chapter for the investigation of OA, and targeted regulation of it is springing up as an attractive and promising therapeutic tactic for OA. Systematic review registration: https://inplasy.com/inplasy-2023-3-0044/, identifier INPLASY202330044.

Multi-scale analysis provides insights into the roles of ureide permeases in wheat nitrogen use efficiency.

The ureides allantoin and allantoate serve as nitrogen (N) transport compounds in plants, and more recently, allantoin has been shown to play a role in signaling. In planta, tissue ureide levels are controlled by the activity of enzymes of the purine degradation pathway and by ureide transporters called ureide permeases (UPS). Little is known about the physiological function of UPS proteins in crop plants, and especially in monocotyledon species. Here, we identified 13 TaUPS genes in the wheat (Triticum aestivum L.) genome. Phylogenetic and genome location analyses revealed a close relationship of wheat UPSs to orthologues in other grasses and a division into TaUPS1, TaUPS2.1, and TaUPS2.2 groups, each consisting of three homeologs, with a total of four tandem duplications. Expression, localization, and biochemical analyses resolved spatio-temporal expression patterns of TaUPS genes, transporter localization at the plasma membrane, and a role for TaUPS2.1 proteins in cellular import of ureides and phloem and seed loading. In addition, positive correlations between TaUPS1 and TaUPS2.1 transcripts and ureide levels were found. Together the data support that TaUPSs function in regulating ureide pools at source and sink, along with source-to-sink transport. Moreover, comparative studies between wheat cultivars grown at low and high N strengthened a role for TaUPS1 and TaUPS2.1 transporters in efficient N use and in controlling primary metabolism. Co-expression, protein-protein interaction, and haplotype analyses further support TaUPS involvement in N partitioning, N use efficiency, and domestication. Overall, this work provides a new understanding on UPS transporters in grasses as well as insights for breeding resilient wheat varieties with improved N use efficiency.

"Cross-talk" between gut microbiome dysbiosis and osteoarthritis progression: a systematic review.

Objectives: The aim of this systematic review was to summarize the available literature on gut microbiome (GMB) and osteoarthritis (OA), analyze the correlation between GMB and OA, and explore potential underlying mechanisms. Methods: A systematic search of the PubMed, Embase, Cochrane, and Web of Science with the keywords "Gut Microbiome" and "Osteoarthritis" was conducted to identify the human and animal studies exploring the association between GMB and OA. The retrieval time range was from the database inception to July 31, 2022. Studies reported the other arthritic diseases without OA, reviews, and studies focused on the microbiome in other parts of the body with OA, such as oral or skin, were excluded. The included studies were mainly reviewed for GMB composition, OA severity, inflammatory factors, and intestinal permeability. Results: There were 31 studies published met the inclusion criteria and were analyzed, including 10 human studies and 21 animal studies. Human and animal studies have reached a consistent conclusion that GMB dysbiosis could aggravate OA. In addition, several studies have found that alterations of GMB composition can increase intestinal permeability and serum levels of inflammatory factors, while regulating GMB can alleviate the changes. Owing to the susceptibility of GMB to internal and external environments, genetics, and geography, the included studies were not consistent in GMB composition analysis. Conclusion: There is a lack of high-quality studies evaluating the effects of GMB on OA. Available evidence indicated that GMB dysbiosis aggravated OA through activating the immune response and subsequent induction of inflammation. Future studies should focus on more prospective, cohort studies combined with multi-omics to further clarify the correlation.

LncRNA XLOC_015548 affects the proliferation and differentiation of myoblasts via the MAPK signaling pathway.

In recent years, an increasing number of studies have reported that long non-coding RNAs (lncRNAs) play essential regulatory roles in myogenic differentiation. In this study, a specific LncRNA XLOC_015548 (Lnc000280) was identified. However, little research has explored its mechanism of action by constructing XLOC_015548 gene editing cell models. In this study, relevant sequences were obtained according to the RNA-seq results. Subsequently, XLOC_015548 knockdown and over-expression lentiviral vectors were constructed, and the C2C12 myoblast cell line was transfected to prepare the XLOC_015548 gene-edited myoblast model. The in vitro analysis revealed that over-expression of XLOC_015548 significantly promoted the proliferation and differentiation of myoblasts and the formation of myotubes, whereas the opposite result was obtained in the knockdown group. XLOC_015548 regulated myogenic differentiation and affected the expression of myogenic differentiation regulators such as Myod, myogenin, and MyHC. Regarding the signaling pathway, we found that XLOC_015548 correlated with the phosphorylation level of MAPK/MEK/ERK pathway proteins. And the degree of phosphorylation was positively correlated with the protein expression of myogenic differentiation regulators. In conclusion, a new gene-edited myoblast model was constructed based on the lncRNA regulator XLOC_015548. The in vitro cell experiments verified that XLOC_015548 had regulatory effects on muscle growth and myoblast differentiation. These findings provide a laboratory foundation for the clinical application of lncRNAs as regulatory factors in the treatment of disuse muscle atrophy.

Short-Term Outcomes of Enhanced Recovery after Surgery (ERAS) for Ankle Fracture Patients: A Single-Center Retrospective Cohort Study.

OBJECTIVE: Enhanced recovery after surgery (ERAS) has been successfully adopted for the improvement of medical quality and efficacy in many diseases, but the effect thereof for ankle fracture patients can vary. The aim of the present study was to explore the short-term postoperative outcomes of ERAS among ankle fracture patients. METHODS: The present study was a retrospective cohort study conducted between January 2019 and May 2019. One hundred and sixty ankle fracture participations (58 males and 102 females, aged 41.71 ± 14.51 years) were included. The participants treated with open reduction and internal fixation were divided into two groups (non-ERAS vs. ERAS) depending on whether ERAS was applied. Postoperative outcomes included American Orthopedic Foot and Ankle Society (AOFAS) score, length of stay (LOS), hospital cost, complications, and consumption of opioids. To assess the association between the groups and outcomes, generalized estimating equation (GEE) modeling and multivariable linear regression analysis were performed. RESULTS: The average follow-up periods of the participations were 24 months postoperatively. No significant differences were detected between the non-ERAS group and ERAS group with respect to the demographic of patients in terms of gender, age, Danis-Weber classification of fracture, dislocation of ankle joint, and comorbidity (P > 0.05). Significant differences in terms of a higher AOFAS score were found in the ERAS group compared with the non-ERAS group (6.73, 95% CI, 5.10-8.37, p < 0.001) at 3 months postoperatively (PO3M) and (4.73, 95% CI, 3.02-6.45, p < 0.001) at 6 months postoperatively (PO6M). However, similar AOFAS scores were found at 12 months postoperatively (PO12M) (0.28, 95% CI, -0.32 to 0.89, P > 0.05) and at 24 months postoperatively (PO24M) (0.56, 95% CI, -0.07 to 1.19, P > 0.05). Additionally, the GEE analysis and group-by-time interaction of AOFAS score revealed that the ERAS protocol could facilitate faster recovery for ankle fracture patients, with higher PO3M and PO6M (both P < 0.05). At the same time, significant differences in terms of a shorter length of stay (-3.19, 95% CI, -4.33 to -2.04, P < 0.01) and less hospital cost (-6501.81, 95% CI, -10955.21 to -2048.42, P < 0.01) were found in the ERAS group compared with the non-ERAS group. CONCLUSION: By reducing LOS and hospital cost, the ERAS protocol might improve the medical quality and efficacy. The present study can provide a realistic evaluation and comparison of the ERAS protocol among ankle fracture patients, and ultimately guide clinical decision making.

Effects of elevated atmospheric [CO2] on grain starch characteristics in different specialized wheat.

The increasing atmospheric [CO2] poses great challenges to wheat production. Currently, the response of starch characteristics in different specialized wheat cultivars to elevated [CO2], as well as the underlying physiological and molecular mechanisms remains unclear. Therefore, an experiment was conducted with open-top chambers to study the effects of ambient [CO2] [a(CO2)] and elevated [CO2] [e(CO2)] on photosynthetic performance, yield and starch characteristics of bread wheat (Zhengmai 369, ZM369) and biscuit wheat (Yangmai 15, YM15) from 2020 to 2022. The results demonstrated a significant improvement in photosynthetic performance, yield, amylose and amylopectin content, volume ratio of large granules under e[CO2]. Moreover, e[CO2] upregulated the gene expression and enzyme activities of GBSS (Granule-bound starch synthase) and SSS (Soluble starch synthase), increased starch pasting viscosity, gelatinization enthalpy and crystallinity. Compared to YM15, ZM369 exhibited a higher upregulation of GBSSI, greater increase in amylose content and volume ratio of large granules, as well as higher gelatinization enthalpy and crystallinity. However, ZM369 showed a lower increase in amylopectin content and a lower upregulation of SSSI and SSSII. Correlation analysis revealed amylose and amylopectin content had a positive correlation with GBSS and SSS, respectively, a significant positively correlation among the amylose and amylopectin content, starch granule volume, and pasting properties. In conclusion, these changes may enhance the utilization value of biscuit wheat but exhibit an opposite effect on bread wheat. The results provide a basis for selecting suitable wheat cultivars and ensuring food security under future climate change conditions.

SOX12 Promotes Stem Cell-Like Phenotypes and Osteosarcoma Tumor Growth by Upregulating JAGGED1.

SOX12 plays a role in promoting the growth of some tumors; however, its role in osteosarcoma remains unclear. From gene expression omnibus (GEO) and tumor alterations relevant for genomics-driven therapy (TARGET) databases, Kaplan-Meier analyses were conducted to establish relationships between SOX12 expression and osteosarcoma survival and recurrence in osteosarcoma patients. We also performed in vitro and in vivo assays to determine SOX12 function in osteosarcoma etiology. SOX12 expression was increased in osteosarcoma; high SOX12 expression levels were related to a poor prognosis and a high disease recurrence in patients. Moreover, SOX12 expression in osteosarcoma cell lines was increased, similar to osteosarcoma cancer stem cells. We also observed that SOX12 knockdown inhibited the spheroidization and expression of stemness markers in osteosarcoma cells and tumor formation in nude mice. In addition, SOX12 knockdown inhibited JAGGED1 and HES1 expression. Similarly, JAGGED1 knockdown also inhibited the formation of osteosarcoma cancer stem cells into pellets and reduced the expression of stemness markers and tumor formation capabilities in nude mice. Finally, during SOX12 knockdown, JAGGED1 overexpression rescued osteosarcoma cells from spheroidizing. SOX12 promotes stem cell-like phenotypes and osteosarcoma tumor growth by upregulating JAGGED1.

A New Perspective on the Role of Glutamine Synthetase in Nitrogen Remobilization in Wheat (Triticum aestivum L.).

Glutamine synthetase (GS), a key enzyme in plant nitrogen metabolism, is closely related to nitrogen remobilization. However, how GS isoforms participate in nitrogen remobilization remains unclear. Here, the spatiotemporal expression of the TaGS gene family after anthesis was investigated, and the results showed that TaGS1;1 was mainly encoded by TaGS1;1-6A, while the other isozymes were mainly encoded by TaGS localized on the A and D subgenomes. TaGS1;2-4A/4D had the highest expression level, especially in rachis and peduncle. Furthermore, immunofluorescence showed TaGS1;2 was located in the phloem of rachis and peduncle. GUS (ß-glucuronidase) staining confirmed that ProTaGS1;2-4A/4D::GUS activity was mainly present in the vascular system of leaves, roots, and petal of Arabidopsis. Ureides, an important transport form of nitrogen, were mainly synthesized in flag leaves and transported to grains through the phloem of peduncle and rachis during grain filling. TaAAH, which encodes the enzyme that degrades ureides to release NH4+, had a higher expression in rachis and peduncle and was synchronized with the increase in NH4+ concentration in phloem, indicating that NH4+ in phloem is from ureide degradation. Taking the above into account, TaGS1;2, which is highly expressed in the phloem of peduncle and rachis, may participate in N remobilization by assimilating NH4+ released from ureide degradation.

Transcriptomic, proteomic, and physiological studies reveal key players in wheat nitrogen use efficiency under both high and low nitrogen supply.

The effective use of available nitrogen (N) to improve crop grain yields provides an important strategy to reduce environmental N pollution and promote sustainable agriculture. However, little is known about the common genetic basis of N use efficiency (NUE) at varying N availability. Two wheat (Triticum aestivum L.) cultivars were grown in the field with high, moderate, and low N supply. Cultivar Zhoumai 27 outperformed Aikang 58 independent of the N supply and showed improved growth, canopy leaf area index, flag leaf surface area, grain number, and yield, and enhanced NUE due to both higher N uptake and utilization efficiency. Further, transcriptome and proteome analyses were performed using flag leaves that provide assimilates for grain growth. The results showed that many genes or proteins that are up- or down-regulated under all N regimes are associated with N and carbon metabolism and transport. This was reinforced by cultivar differences in photosynthesis, assimilate phloem transport, and grain protein/starch yield. Overall, our study establishes that improving NUE at both high and low N supply requires distinct adjustments in leaf metabolism and assimilate partitioning. Identified key genes/proteins may individually or concurrently regulate NUE and are promising targets for maximizing crop NUE irrespective of the N supply.

Localization, Gene Expression, and Functions of Glutamine Synthetase Isozymes in Wheat Grain (Triticum aestivum L.).

Glutamine synthetase (GS) plays a major role in plant nitrogen metabolism, but the roles of individual GS isoforms in grains are unknown. Here, the localization and expression of individual TaGS isozymes in wheat grain were probed with TaGS isoenzyme-specific antibodies, and the nitrogen metabolism of grain during the grain filling stage were investigated. Immunofluorescence revealed that TaGS1;1, TaGS1;3, and TaGS2 were expressed in different regions of the embryo. In grain transporting tissues, TaGS1;2 was localized in vascular bundle; TaGS1;2 and TaGS1;1 were in chalaza and placentochalaza; TaGS1;1 and TaGS1;3 were in endosperm transfer cells; and TaGS1;3 and TaGS2 were in aleurone layer. GS exhibited maximum activity and expression at 8 days after flowering (DAF) with peak glutamine content in grains; from then, NH 4 + increased largely from NO 3 - reduction, glutamate dehydrogenase (GDH) aminating activity increased continuously, and the activities of GS and glutamate synthase (GOGAT) decreased, while only TaGS1;3 kept a stable expression in different TaGS isozymes. Hence, GS-GOGAT cycle and GDH play different roles in NH 4 + assimilation of grain in different stages of grain development; TaGS1;3, located in aleurone layer and endosperm transfer cells, plays a key role in Gln into endosperm for gluten synthesis. At 30 DAF, grain amino acids are mainly transported from maternal phloem.

Nitrogen Regulating the Expression and Localization of Four Glutamine Synthetase Isoforms in Wheat (Triticum aestivum L.).

Glutamine synthetase (GS), the key enzyme in plant nitrogen assimilation, is strictly regulated at multiple levels, but the most relevant reports focus on the mRNA level. Using specific antibodies as probes, the effects of nitrogen on the expression and localization of individual wheat GS (TaGS) isoforms were studied. In addition to TaGS2, TaGS1;1 with high affinity to substrate and TaGS1;3 with high catalytic activity were also localized in mesophyll, and may participate in cytoplasmic assimilation of ammonium (NH4+) released from photorespiration or absorbed by roots; TaGS1;2 was localized in xylem of leaves. In roots, although there were hundreds of times more TaGS1;1 than TaGS1;2 transcripts, the amount of TaGS1;1 subunit was not higher than that of TaGS1;2; NH4+ inhibited TaGS1;1 expression but stimulated TaGS1;3 expression. In root tips, nitrate stimulated TaGS1;1, TaGS1;3, and TaGS2 expression in meristem, while NH4+ promoted tissue differentiation and TaGS1;2 expression in endodermis and vascular tissue. Only TaGS1;2 was located in vascular tissue of leaves and roots, and was activated by glutamine, suggesting a role in nitrogen transport. TaGS1;3 was induced by NH4+ in root endodermis and mesophyll, suggesting a function in relieving NH4+ toxicity. Thus, TaGS isoforms play distinct roles in nitrogen assimilation for their different kinetic properties, tissue locations, and response to nitrogen regimes.

Towards identification of molecular mechanism in which the overexpression of wheat cytosolic and plastid glutamine synthetases in tobacco enhanced drought tolerance.

Glutamine synthetases (GS) play an essential role in Nitrogen assimilation. Nonetheless, information respecting the molecular functions of GS in drought tolerance (DT) is limited. Here we show that overexpressing cytosolic GS1 or plastidic GS2 gene in tobacco enhanced DT of both root and leaf tissues of the two transgenic seedlings (named as GS1-TR and GS2-TR). RNA-seq analysis on root tissues showed that 83 aquaporin (AQP) genes were identified. Among them, 37 differential expression genes (DEGs) were found in the GS1-TR roots under normal condition, and all were down-regulated; no any DEGs in the GS2-TR roots were found. Contrastingly, under drought, 28 and 32 DEGs of AQP were up-regulated in GS1-TR and GS2-TR roots, respectively. GC-MS analysis on leaf tissues showed that glutamine (Gln) concentrations were negatively correlated AQP expressions in the all four conditions, which suggests that Gln, as a signal molecule, can negatively regulate many AQP expressions. Prestress accumulation of sucrose and proline (Pro) and chlorophyll, and had higher activities of ROS scavengers also contribute the plant DT in both of the two transgenic plants under drought. In addition, 5-aminolevulinic acid (ALA) was up-accumulated in GS2-TR leaves solely under normal condition, which leads to its net photosynthetic rate higher than that in GS1-TR leaves. Last but not the less, the PYL-PP2C-SnRK2 core ABA-signaling pathway was uniquely activated in GS1-TR independent of drought stress (DS). Therefore, our results suggest a possible model reflecting how overexpression of wheat TaGS1 and TaGS2 regulate plant responses to drought.