Canagliflozin alleviates pulmonary hypertension by activating PPARγ and inhibiting its S225 phosphorylation.

Pulmonary hypertension (PH) is a progressive fatal disease with no cure. Canagliflozin (CANA), a novel medication for diabetes, has been found to have remarkable cardiovascular benefits. However, few studies have addressed the effect and pharmacological mechanism of CANA in the treatment of PH. Therefore, our study aimed to investigate the effect and pharmacological mechanism of CANA in treating PH. First, CANA suppressed increased pulmonary artery pressure, right ventricular hypertrophy, and vascular remodeling in both mouse and rat PH models. Network pharmacology, transcriptomics, and biological results suggested that CANA could ameliorate PH by suppressing excessive oxidative stress and pulmonary artery smooth muscle cell proliferation partially through the activation of PPARγ. Further studies demonstrated that CANA inhibited phosphorylation of PPARγ at Ser225 (a novel serine phosphorylation site in PPARγ), thereby promoting the nuclear translocation of PPARγ and increasing its ability to resist oxidative stress and proliferation. Taken together, our study not only highlighted the potential pharmacological effect of CANA on PH but also revealed that CANA-induced inhibition of PPARγ Ser225 phosphorylation increases its capacity to counteract oxidative stress and inhibits proliferation. These findings may stimulate further research and encourage future clinical trials exploring the therapeutic potential of CANA in PH treatment.

Nitrogen Sources Reprogram Carbon and Nitrogen Metabolism to Promote Andrographolide Biosynthesis in Andrographis paniculata (Burm.f.) Nees Seedlings.

Carbon (C) and nitrogen (N) metabolisms participate in N source-regulated secondary metabolism in medicinal plants, but the specific mechanisms involved remain to be investigated. By using nitrate (NN), ammonium (AN), urea (UN), and glycine (GN), respectively, as sole N sources, we found that N sources remarkably affected the contents of diterpenoid lactone components along with C and N metabolisms reprograming in Andrographis paniculata, as compared to NN, the other three N sources raised the levels of 14-deoxyandrographolide, andrographolide, dehydroandrographolide (except UN), and neoandrographolide (except AN) with a prominent accumulation of farnesyl pyrophosphate (FPP). These N sources also raised the photosynthetic rate and the levels of fructose and/or sucrose but reduced the activities of phosphofructokinase (PFK), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), phosphoenolpyruvate carboxylase (PEPC) and pyruvate dehydrogenase (PDH). Conversely, phosphoenolpyruvate carboxykinase (PEPCK) and malate enzyme (ME) activities were upregulated. Simultaneously, citrate, cis-aconitate and isocitrate levels declined, and N assimilation was inhibited. These results indicated that AN, UN and GN reduced the metabolic flow of carbohydrates from glycolysis into the TCA cycle and downstream N assimilation. Furthermore, they enhanced arginine and GABA metabolism, which increased C replenishment of the TCA cycle, and increased ethylene and salicylic acid (SA) levels. Thus, we proposed that the N sources reprogrammed C and N metabolism, attenuating the competition of N assimilation for C, and promoting the synthesis and accumulation of andrographolide through plant hormone signaling. To obtain a higher production of andrographolide in A. paniculata, AN fertilizer is recommended in its N management.

The psoas muscle density as a predictor of postoperative complications in elderly patients undergoing rectal cancer resection.

Background: Muscle depletion that impairs normal physiological function in elderly patients leads to poor prognosis. This study aimed to evaluate the association between total abdominal muscle area (TAMA), total psoas area (TPA), psoas muscle density (PMD), and short-term postoperative complications in elderly patients with rectal cancer. Methods: All elderly patients underwent rectal cancer resection with perioperative abdominal computed tomography (CT). Complications were assessed according to the Clavien-Dindo classification. Severe complications were defined as grade III-V following the Clavien-Dindo classification. Univariate and multivariate analyses were performed to evaluate risk factors of short-term severe postoperative complications. Results: The cohort consisted of 191 patients with a mean age of 73.60 ± 8.81 years. Among them, 138 (72.25%) patients had Clavien-Dindo 0- II, 53 (27.75%) patients had severe postoperative complications (Clavien-Dindo III-V), and 1(0.52%) patient died within 30 days of surgery. PMD was significantly higher in the Clavien-Dindo 0-II cohort compared to the Clavien-Dindo III-V cohort (p=0.004). Nevertheless, TAMA and TPA failed to exhibit significant differences. Moreover, the multivariate regression analysis implied that advanced age [OR 1.07 95%CI (1.02-1.13) p=0.013], male [OR 5.03 95%CI (1.76-14.41) p=0.003], high charlson comorbidity index (CCI) score [OR 3.60 95%CI (1.44-9.00) p=0.006], and low PMD [OR 0.94 95%CI (0.88-0.99) p=0.04] were independent risk factors of Clavien-Dindo III-V. Conclusion: Preoperative assessment of the PMD on CT can be a simple and practical method for identifying elderly patients with rectal cancer at risk for severe postoperative complications.

Exogenous γ-aminobutyric acid (GABA) alleviates nitrogen deficiency by mediating nitrate uptake and assimilation in Andrographis paniculata seedlings.

γ-Aminobutyric acid (GABA) plays significant metabolic and signaling roles in plant stress responses. Recent studies have proposed that GABA alleviates plant nitrogen (N) deficient stress; however, the mechanism by which GABA mediates plant N deficiency adaptation remains not yet well understood. Herein we found in a medicinal plant Andrographis paniculata that 5 mmol L-1 exogenous GABA promoted plant growth under N deficient (1 mmol L-1 NO3-) condition, with remarkably increments in total N and NO3- concentrations in plants. GABA increased N assimilation and protein synthesis by up-regulating the activities and expression of N metabolic enzymes. GABA also increased the accumulation of α-ketoglutarate and malate, which could facilitate the assimilation of NO3-. Inhibition of NR by Na2WO4 counteracted the promoting effects of GABA on plant growth, and the effects of GABA were not affected by L-DABA and 3-MP, the inhibitors of GABA transaminase (GABA-T) and glutamate decarboxylase (GAD), respectively. These results suggested that the nutritional role of GABA was excluded in promoting plant growth under low N condition. The results of 15N isotopic tracing and NRTs transcription indicated that exogenous GABA could up-regulate NRT2.4 and NRT3.2 to increase plant NO3- uptake under N deficient condition. Interestingly, primidone, an inhibitor of GABA receptor, impeded the effects of GABA on plant growth and N accumulation. Thus, our results revealed that exogenous GABA acted as a signal to up-regulate NRTs via its receptor to increase NO3- uptake, and subsequently promoted NO3- assimilation to alleviate N deficiency in A. paniculata.

Survival benefits of para-aortic lymphadenectomy in colorectal cancer with clinically suspected para-aortic lymph node metastasis: a meta-analysis and systematic review.

BACKGROUND AND OBJECTIVES: In patients with colorectal cancer and clinically suspected para-aortic lymph node metastasis, the survival benefit of para-aortic lymphadenectomy is unknown. We conducted a meta-analysis and systematic review to investigate it. METHODS: PubMed, Web of Science, and EMBASE were searched until January 2000 to April 2022 to identify studies reporting overall survivals, complication rates, and hazard ratios of prognostic factors in patients with colorectal cancer undergoing para-aortic lymphadenectomy, and those data were pooled. RESULTS: Twenty retrospective studies (1021 patients undergoing para-aortic lymphadenectomy) met the inclusion criteria. Meta-analysis indicates that participants undergoing para-aortic lymphadenectomy were associated with 5-year survival benefit, compared to those not receiving para-aortic lymphadenectomy (odds ratio = 3.73, 95% confidence interval: 2.05-6.78), but there was no significant difference in complication rate (odds ratio = 0.97, 95% confidence interval: 0.46-2.08). Further analysis of para-aortic lymphadenectomy group showed that 5-year survival of the positive group with pathologically para-aortic lymph node metastasis was lower than that of the negative group (odds ratio = 0.19, 95% confidence interval: 0.11-0.31). Moreover, complete resection (odds ratio = 5.26, 95% confidence interval: 2.02-13.69), para-aortic lymph node metastasis (≤4) (hazard ratio = 1.88, 95% confidence interval: 0.97-3.62), and medium-high differentiation (hazard ratio = 2.98, 95% confidence interval: 1.48-5.99) were protective factors for survival. Preoperative extra-retroperitoneal metastasis was associated with poorer relapse-free survival (hazard ratio = 1.85, 95% confidence interval: 1.10-3.10). CONCLUSION: Para-aortic lymphadenectomy had promising clinical efficacy in prolonging survival rather than complication rate in patients with colorectal cancer and clinically diagnostic para-aortic lymph node metastasis. Further prospective studies should be performed. TRIAL REGISTRATION: PROSPERO: CRD42022379276.

[Comparison on volatile components between Artemisiae Verlotori Folium and Artemisiae Argyi Folium based on GC-MS and chemometrics].

Artemisiae Argyi Folium is commonly used in clinical practice. Artemisiae Verlotori Folium, the dried leaves of Artemisia verlotorum, is often used as a folk substitute for Artemisiae Argyi Folium in Lingnan area. In this study, gas chromatography-triple quadrupole mass spectrometry(GC-MS) was used to detect the volatile oil components of 27 samples of Artemisiae Verlotori Folium and 13 samples of Artemisiae Argyi Folium, and the volatile components were compared between the two species. The internal standard method was combined with multi-reaction monitoring mode(MRM) to determine the content of six major volatile components. Hierarchical clustering analysis(HCA) and orthogonal partial least squares-discriminant analysis(OPLS-DA) were carried out for the content data. The results showed that the Artemisiae Argyi Folium samples had higher content and more abundant volatile oils than the Artemisiae Verlotori Folium samples. Artemisiae Argyi Folium mainly had the components with lower boiling points, while Artemisiae Verlotori Folium mainly had the components with higher boiling points. Terpenoids were the main volatile components in Artemisiae Verlotori Folium(mainly sesquiterpenoids) and Artemisiae Argyi Folium(monoterpenoids). In addition, Artemisiae Argyi Folium had higher content of oxygen-containing derivatives than Artemisiae Verlotori Folium. Furthermore, the stoichiometric analysis showed that the two species could be distinguished by both HCA and OPLS-DA, indicating that the volatile components of the two were significantly different. This study can provide a scientific basis for the quality evaluation and data support for the local rational application of Artemisiae Verlotori Folium in Lingnan.

Concentration-dependent dual effects of exogenous sucrose on nitrogen metabolism in Andrographis paniculata.

The effects of exogenous sucrose (Suc) concentrations (0, 0.5, 1, 5, 10 mmol L-1) on carbon (C) and nitrogen (N) metabolisms were investigated in a medicinal plant Andrographis paniculata (Chuanxinlian). Suc application with the concentration of 0.5-5 mmol L-1 significantly promoted plant growth. In contrast, 10 mmol L-1 Suc retarded plant growth and increased contents of anthocyanin and MDA and activity of SOD in comparison to 0.5-5 mmol L-1 Suc. Suc application increased contents of leaf soluble sugar, reducing sugar and trerhalose, as well as isocitrate dehydrogenase (ICDH) activity, increasing supply of C-skeleton for N assimilation. However, total leaf N was peaked at 1 mmol L-1 Suc, which was consistent with root activity, suggesting that exogenous Suc enhanced root N uptake. At 10 mmol L-1 Suc, total leaf N and activities of glutamine synthase (GS), glutamate synthase (GOGAT), NADH-dependent glutamate dehydrogenase (NADH-GDH) and glutamic-pyruvic transaminase (GPT) were strongly reduced but NH4+ concentration was significantly increased. The results revealed that exogenous Suc is an effective stimulant for A. paniculata plant growth. Low Suc concentration (e.g. 1 mmol L-1) increased supply of C-skeleton and promoted N uptake and assimilation in A. paniculata plant, whereas high Suc concentration (e.g. 10 mmol L-1) uncoupled C and N metabolisms, reduced N metabolism and induced plant senescence.

Single-Cell Sequencing to Unveil the Mystery of Embryonic Development.

Embryonic development is a fundamental physiological process that can provide tremendous insights into stem cell biology and regenerative medicine. In this process, cell fate decision is highly heterogeneous and dynamic, and investigations at the single-cell level can greatly facilitate the understanding of the molecular roadmap of embryonic development. Rapid advances in the technology of single-cell sequencing offer a perfectly useful tool to fulfill this purpose. Despite its great promise, single-cell sequencing is highly interdisciplinary, and successful applications in specific biological contexts require a general understanding of its diversity as well as the advantage versus limitations for each of its variants. Here, the technological principles of single-cell sequencing are consolidated and its applications in the study of embryonic development are summarized. First, the technology basics are presented and the available tools for each step including cell isolation, library construction, sequencing, and data analysis are discussed. Then, the works that employed single-cell sequencing are reviewed to investigate the specific processes of embryonic development, including preimplantation, peri-implantation, gastrulation, and organogenesis. Further, insights are provided on existing challenges and future research directions.

[Herbalogical study on historical evolution of collection, processing and efficacy of Citri Exocarpium Rubrum and Citri Grandis Exocarpium].

In ancient times, the original plants of Citri Exocarpium Rubrum and Citri Grandis Exocarpium had experienced succession and change, including tangerine(Citrus reticulata), pomelo(C. grandis), and Huazhou pomelo(C. grandis 'Tomentosa'), a specific cultivar of C. grandis produced in Huazhou, Guangdong. Before the Qing Dynasty, tangerine was the main original plant, while Huazhou pomelo came to the fore in the Qing Dynasty. In the 1950 s and 1960 s, the producing area of Huazhou pomelo was destroyed, and thus it had to be supplemented with pomelo. From then on, C. grandis 'Tomentosa' and C. grandis were both listed as the original plants of Citri Grandis Exocarpium in the Chinese Pharmacopoeia. This paper reviewed the historical evolution of the collection, processing, and efficacy of Citri Exocarpium Rubrum and Citri Grandis Exocarpium. The research showed that:(1)The harvest time of the original plants of Citri Grandis Exocarpium and Citri Grandis Exocarpium had changed from maturity to immaturity. The collection and processing of Citri Exocarpium Rubrum was first recorded in the Illustrated Classics of Materia Medica in the Song Dynasty. During the Ming and Qing Dynasties, the mesocarp of Citri Exocarpium Rubrum needed to be removed completely, and Citri Grandis Exocarpium from C. grandis 'Tomentosa' was processed into different specifications such as seven-piece, five-piece, and single piece. Furthermore, processed young fruits of Huazhou pomelo appeared.(2)Citri Exocarpium Rubrum and Citri Grandis Exocarpium were processed with carp skin for the first time in the Master Lei's Discourse on Medicinal Processing. It was suggested that carp skin might be helpful for eliminating bones stuck in throat. During the Song, Jin, and Yuan Dynasties, some other processing methods such as ba-king, stir-frying, and salt-processing appeared. Honey, soil, ginger juice, and alum were firstly used as adjuvants for the processing in the Ming and Qing Dynasties. Citri Exocarpium Rubrum was mainly prepared with salt in order to improve the effect of lowering Qi, while it was unnecessary for Citri Grandis Exocarpium from C. grandis 'Tomentosa' because of its obvious effect of lowering Qi and eliminating phlegm. The stir-frying and honey-frying methods helped reduce the strong effect of Citri Grandis Exocarpium from C. grandis 'Tomentosa'.(3)According to the application of Citri Exocarpium Rubrum and Citri Grandis Exocarpium in history, their medicinal use began in Han and Tang Dynasties, developed in Song, Jin, and Yuan Dynasties, and matured in Ming and Qing Dynasties. Citri Grandis Exocarpium from C. grandis 'Tomentosa' was originally applied in Ming and Qing Dynasties, and it still plays an important in role treating COVID-19 nowadays. Moreover, Citri Grandis Exocarpium from C. grandis had cold medicinal property, while Citri Grandis Exocarpium from C. grandis 'Tomentosa' had warm medicinal property, and thus they should not be treated the same. At present, Huazhou pomelo has a certain production scale. Therefore, it is recommended that in the next edition of Chinese Pharmacopoeia, only C. grandis 'Tomentosa' should be included as the original plant of Citri Grandis Exocarpium, and C. grandis should be deleted. The results are conducive to the further development and utilization of Citri Exocarpium Rubrum and Citri Grandis Exocarpium, and support the rational use of Citri Grandis Exocarpium and its processed products.

Sulfur Regulates the Trade-Off Between Growth and Andrographolide Accumulation via Nitrogen Metabolism in Andrographis paniculata.

Nitrogen (N) and sulfur (S) are essential mineral nutrients for plant growth and metabolism. Here, we investigated their interaction in plant growth and andrographolide accumulation in medicinal plant Andrographis paniculata grown at different N (4 and 8 mmol·L-1) and S concentration levels (0.1 and 2.4 mmol L-1). We found that increasing the S application rate enhanced the accumulation of andrographolide compounds (AGCs) in A. paniculata. Simultaneously, salicylic acid (SA) and gibberellic acid 4 (GA4) concentrations were increased but trehalose/trehalose 6-phosphate (Tre/Tre6P) concentrations were decreased by high S, suggesting that they were involved in the S-mediated accumulation of AGCs. However, S affected plant growth differentially at different N levels. Metabolite analysis revealed that high S induced increases in the tricarboxylic acid (TCA) cycle and photorespiration under low N conditions, which promoted N assimilation and S metabolism, and simultaneously increased carbohydrate consumption and inhibited plant growth. In contrast, high S reduced N and S concentrations in plants and promoted plant growth under high N conditions. Taken together, the results indicated that increasing the S application rate is an effective strategy to improve AGC accumulation in A. paniculata. Nevertheless, the interaction of N and S affected the trade-off between plant growth and AGC accumulation, in which N metabolism plays a key role.

Organic nitrogen sources promote andrographolide biosynthesis by reducing nitrogen metabolism and increasing carbon accumulation in Andrographis paniculata.

Nitrogen (N) form affects secondary metabolites of medicinal plants, but the physiological and molecular mechanisms remain largely unknown. To fully understand the response of andrographolide biosynthesis to different N forms in Andrographis paniculata, the plants were fed with nutritional solution containing sole N source of nitrate (NO3-), ammonium (NH4+), urea or glycine (Gly), and the growth, carbon (C) and N metabolisms and andrographolide biosynthesis were analyzed. We found that plants grown in urea and Gly performed greater photosynthetic rate and photosynthetic N use efficiency (PNUE) than those grown in NO3- and NH4+. Organic N sources reduced the activities of enzymes involving in C and N metabolisms such as glutamine synthase (GS), glutamate synthase (GOGAT) and NADH-dependent glutamate dehydrogenase (NADH-GDH), invertase (INV), isocitrate dehydrogenase (ICDH) and glycolate oxidase (GO), resulting in reduced depletion of carbohydrates and increased starch accumulation. However, they enhanced andrographolide content by up-regulating the key genes in its biosynthetic pathway including HMGR, DXS, GGPS and ApCPS. Besides, NH4+ decreased leaf SPAD value, contents of soluble protein and amino acids and GO activity, but increased photosynthetic rate and contents of soluble sugar and starch in comparison to NO3-. Andrographolide biosynthesis was also up-regulated. The results revealed that increasing accumulation of carbohydrates, especially starch, was beneficial to the biosynthesis of andrographolide; organic N sources decreased carbohydrate depletion by reducing N metabolism, and promoted plant growth and andrographolide biosynthesis synergistically.

[Herbalogical study on historical evolution of Juhong and Huajuhong].

In ancient times, there were two types of "Juhong" came from the tangerines(Citrus reticulata) and the pomelos(C. grandis and its cultivars), which corresponded to Juhong and Huajuhong recorded in the Chinese Pharmacopoeia respectively. In different periods, Juhong basically came from the same species and the same medicinal parts, but there were also some differences. This article sorted out the ancient and modern literature, under the guidance of "Succession theory of Medicinal materials varieties" and "Change theory of Medicinal materials varieties"(XIE Zong-wan), and combined with field investigation, the evolution and reasons of the original plants and medicinal parts of Juhong were analyzed. In the Han Dynasty and before, the peel of tangerines and pomelos were both used as medicine. In the Southern and Northern Dynasties, the way tangerine peel was used was dried and aged, and then "soaked in hot water and scraped off the mesocarp", which had the essence of only using exocarp as medicine of Juhong already, and its original plant was C. reticalata. In the Song Dynasty, the name of "Juhong" and its medicinal usage were recorded in book on materia medica, and the species and medicinal parts of tangerine were inherited from the previous dynasties. The way tangerine peel was used was only dried and aged without removing the mesocarp. The medicinal material obtained by the way was called Chenpi(dried and aged tangerine peel). The item "Juhong" listing as a separate medicinal material was first recorded in the Collected Discussions from Materia Medica(Bencao Huiyan) in the Ming Dynasty. In the Ming Dynasty, the Dao-di habitat of Juhong was recorded as Guangdong province in most books on materia medica, and the original plants probably were C. reticalata and C. grandis 'Tomentosa'(Huazhou pomelo, a special cultivated species of C. grandis produced in Huazhou, Guangdong, which was recorded in the Chinese Pharmacopoeia as "Huajuhong"), according to the records in the local chronicles. During the Qing Dynasty and the Republic of China, the original plants of Juhong were C. reticalata and C. grandis 'Tomentosa'. Of the two, the latter one was considered as the better. As far the medicinal part, it was still the exocarp, while the whole young fruit of C. grandis 'Tomentosa' began to be used as medicine. After the founding of The People's Republic of China, the exocarps of Citrus reticalata, C. grandis and C. grandis 'Tomentosa' were listed in the Chinese Pharmacopoeia under "Juhong". From the Northern and Southern Dynasties to the Republic of China, C. grandis exocarp was a fake of Juhong. Therefore, it was contradictory to historical records that C. grandis exocarp was listed in the Chinese Pharmacopoeia as Huajuhong. Juhong had been divided into two types as "Juhong" and "Huajuhong" since 1985. The medicinal part of Huajuhong was only the exocarp of immature and nearly mature fruits, but not the whole young fruit, the actual mainstream medicinal part of Huajuhong. The results are helpful to clarify the historical evolution of species and medicinal parts of Juhong and Huajuhong. It is suggested that in the next edition of Chinese Pharmacopoeia, only C. grandis 'Tomentosa' should be included as the original plant of Huajuhong, and C. grandis should be deleted, and the young fruit should be added in the medicinal parts besides the exocarp of immature and nearly mature fruit.

Carbon dots decorated three-dimensionally ordered macroporous bismuth-doped titanium dioxide with efficient charge separation for high performance photocatalysis.

Fast recombination of photo-generated carriers and limited photo-response have greatly hindered the development of TiO2-based photocatalysts. Herein, we present a ternary three-dimensionally ordered macroporous (3DOM) carbon dots (CDs)/Bi:TiO2 photocatalyst, which affords well-designed charge transmission and allows broad-spectrum absorption, thus delivering enhanced photocatalytic performance. The carbon dots act as effective electron extractors to accelerate the separation of electron-hole pairs, and pore engineering of the 3DOM Bi:TiO2 skeleton greatly promotes the response of light in the whole solar spectrum range. Impressively, the 3DOM CDs/Bi:TiO2 catalyst exhibits a greatly enhanced photocatalytic degradation performance toward phenol (92.7% in 2 h), and RhB (96.4% in 40 min) under full-spectra illumination, compared to the pristine 3DOM TiO2. This work provides a new design strategy for the optimization of carriers transmission pathway in high-quality and low-cost photocatalysts.

Crosstalk between autophagy and epithelial-mesenchymal transition and its application in cancer therapy.

Autophagy is a highly conserved catabolic process that mediates degradation of pernicious or dysfunctional cellular components, such as invasive pathogens, senescent proteins, and organelles. It can promote or suppress tumor development, so it is a "double-edged sword" in tumors that depends on the cell and tissue types and the stages of tumor. The epithelial-mesenchymal transition (EMT) is a complex biological trans-differentiation process that allows epithelial cells to transiently obtain mesenchymal features, including motility and metastatic potential. EMT is considered as an important contributor to the invasion and metastasis of cancers. Thus, clarifying the crosstalk between autophagy and EMT will provide novel targets for cancer therapy. It was reported that EMT-related signal pathways have an impact on autophagy; conversely, autophagy activation can suppress or strengthen EMT by regulating various signaling pathways. On one hand, autophagy activation provides energy and basic nutrients for EMT during metastatic spreading, which assists cells to survive in stressful environmental and intracellular conditions. On the other hand, autophagy, acting as a cancer-suppressive function, is inclined to hinder metastasis by selectively down-regulating critical transcription factors of EMT in the early phases. Therefore, the inhibition of EMT by autophagy inhibitors or activators might be a novel strategy that provides thought and enlightenment for the treatment of cancer. In this article, we discuss in detail the role of autophagy and EMT in the development of cancers, the regulatory mechanisms between autophagy and EMT, the effects of autophagy inhibition or activation on EMT, and the potential applications in anticancer therapy.

1-Methylcyclopropene Modulates Physiological, Biochemical, and Antioxidant Responses of Rice to Different Salt Stress Levels.

Salt stress in soil is a critical constraint that affects the production of rice. Salt stress hinders plant growth through osmotic stress, ionic stress, and a hormonal imbalance (especially ethylene), therefore, thoughtful efforts are needed to devise salt tolerance management strategies. 1-Methylcyclopropene (1-MCP) is an ethylene action inhibitor, which could significantly reduce ethylene production in crops and fruits. However, 1-MCPs response to the physiological, biochemical and antioxidant features of rice under salt stress, are not clear. The present study analyzed whether 1-MCP could modulate salt tolerance for different rice cultivars. Pot culture experiments were conducted in a greenhouse in 2016-2017. Two rice cultivars, Nipponbare (NPBA) and Liangyoupeijiu (LYP9) were used in this trial. The salt stress included four salt levels, 0 g NaCl/kg dry soil (control, CK), 1.5 g NaCl/ kg dry soil (Low Salt stress, LS), 4.5 g NaCl/kg dry soil (Medium Salt stress, MS), and 7.5 g NaCl/kg dry soil (Heavy Salt stress, HS). Two 1-MCP levels, 0 g (CT) and 0.04 g/pot (1-MCP) were applied at the rice booting stage in 2016 and 2017. The results showed that applying 1-MCP significantly reduced ethylene production in rice spikelets from LYP9 and NPBA by 40.2 and 23.9% (CK), 44.3 and 28.6% (LS), 28 and 25.9% (MS), respectively. Rice seedlings for NPBA died under the HS level, while application of 1-MCP reduced the ethylene production in spikelets for LYP9 by 27.4% compared with those that received no 1-MCP treatment. Applying 1-MCP improved the photosynthesis rate and SPAD value in rice leaves for both cultivars. 1-MCP enhanced the superoxide dismutase production, protein synthesis, chlorophyll contents (chl a, b, carotenoids), and decreased malondialdehyde, H2O2, and proline accumulation in rice leaves. Application of 1-MCP also modulated the aboveground biomass, and grain yield for LYP9 and NPBA by 19.4 and 15.1% (CK), 30.3 and 24% (LS), 26.4 and 55.4% (MS), respectively, and 34.5% (HS) for LYP9 compared with those that received no 1-MCP treatment. However, LYP9 displayed a better tolerance than NPBA. The results revealed that 1-MCP could be employed to modulate physiology, biochemical, and antioxidant activities in rice plants, at different levels of salt stress, as a salt stress remedy.

Putrescine alleviates aluminum toxicity in rice (Oryza sativa) by reducing cell wall Al contents in an ethylene-dependent manner.

Aluminum (Al3+ ) toxicity in acidic soils limits crop productivity worldwide. In this study, we found that putrescine (PUT) significantly alleviates Al toxicity in rice roots. The addition of 0.1 mM PUT promoted root elongation and reduced the Al content in the root apices of Nipponbare (Nip) and Kasalath (Kas) rice under Al toxicity conditions. Exogenous treatment with PUT reduced the cell wall Al content by reducing polysaccharide (pectin and hemicellulose) levels and pectin methylesterase (PME) activity in roots and decreased the translocation of Al from the external environment to the cytoplasm by downregulating the expression of OsNRAT1, which responsible to encode an Al transporter protein Nrat1 (Nramp aluminum transporter 1). The addition of PUT under Al toxicity conditions significantly inhibited ethylene emissions and suppressed the expression of genes involved in ethylene biosynthesis. Treatment with the ethylene precursor 1-aminocylopropane-1-carboxylic acid (ACC) significantly improved ethylene emission, inhibited root elongation, increased the Al accumulation in root tips and the root cell wall, and increased cell wall pectin and hemicellulose contents in both rice cultivars under Al toxicity conditions. The ethylene biosynthesis antagonist aminoethoxyvinylglycine (AVG, inhibitor of the ACC synthase) had the opposite effect and reduced PME activity. Together, our results show that PUT decreases the cell wall Al contents by suppressing ethylene emissions and decreases the symplastic Al levels by downregulating OsNRAT1 in rice.

Nitric oxide synthase-mediated early nitric oxide burst alleviates water stress-induced oxidative damage in ammonium-supplied rice roots.

BACKGROUND: Nutrition with ammonium (NH4+) can enhance the drought tolerance of rice seedlings in comparison to nutrition with nitrate (NO3-). However, there are still no detailed studies investigating the response of nitric oxide (NO) to the different nitrogen nutrition and water regimes. To study the intrinsic mechanism underpinning this relationship, the time-dependent production of NO and its protective role in the antioxidant defense system of NH4+- or NO3--supplied rice seedlings were studied under water stress. RESULTS: An early NO burst was induced by 3 h of water stress in the roots of seedlings subjected to NH4+ treatment, but this phenomenon was not observed under NO3- treatment. Root oxidative damage induced by water stress was significantly higher for treatment with NO3- than with NH4+ due to reactive oxygen species (ROS) accumulation in the former. Inducing NO production by applying the NO donor 3 h after NO3- treatment alleviated the oxidative damage, while inhibiting the early NO burst by applying the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (c-PTIO) increased root oxidative damage in NH4+ treatment. Application of the nitric oxide synthase (NOS) inhibitor N(G)-nitro-L-arginine methyl ester(L-NAME) completely suppressed NO synthesis in roots 3 h after NH4+ treatment and aggravated water stress-induced oxidative damage. Therefore, the aggravation of oxidative damage by L-NAME might have resulted from changes in the NOS-mediated early NO burst. Water stress also increased the activity of root antioxidant enzymes (catalase, superoxide dismutase, and ascorbate peroxidase). These were further induced by the NO donor but repressed by the NO scavenger and NOS inhibitor in NH4+-treated roots. CONCLUSION: These findings demonstrate that the NOS-mediated early NO burst plays an important role in alleviating oxidative damage induced by water stress by enhancing the antioxidant defenses in roots supplemented with NH4+.

Trade-off of within-leaf nitrogen allocation between photosynthetic nitrogen-use efficiency and water deficit stress acclimation in rice (Oryza sativa L.).

Nitrogen (N) allocation in leaves affects plant photosynthesis-N relationship and adaptation to environmental fluctuations. To reveal the role of leaf N allocation in water deficit stress acclimation in rice, the plants were grown in infertile soil supplying with low N (0.05 g N·kg-1 soil) and high N (0.2 g N·kg-1 soil), and then imposed to water deficit stress (∼75% relative soil water content). We found that the proportion of leaf N allocated in the photosynthetic apparatus was significantly positive correlated with photosynthetic N-use efficiency (PNUE), and that N allocation in the carboxylation system and bioenergetics were the primary two limiting factors of PNUE under the conditions of high N and water deficit stress. PNUE was not significantly affected by water stress in low N condition, but markedly reduced in high N condition. Under low N condition, plants reduced N allocation in the light-harvesting system and increased soluble protein and free amino acids, or reduced N allocation in the cell wall to maintain PNUE under water deficit stress. Under high N, however, plants decreased N allocation in bioenergetics or carboxylation, but increased N allocation in non-photosynthetic components during water stress. Our results reveal that the coordination of leaf N allocation between photosynthetic and non-photosynthetic apparatus, and among the components of the photosynthetic apparatus is important for the trade-off between PNUE and the acclimation of water deficit stress in rice.

Ammonium mitigates Cd toxicity in rice (Oryza sativa) via putrescine-dependent alterations of cell wall composition.

In plants, different forms of nitrogen (NO3- or NH4+) affect nutrient uptake and environmental stress responses. In the present study, we tested whether NO3- and NH4+ affect the ability of rice (Oryza sativa) to tolerate the toxic heavy metal cadmium (Cd). Compared with NO3-, NH4+ treatment significantly increased chlorophyll contents and reduced Cd2+ levels in rice cultivars Nipponbare (japonica) and Kasalath (indica) grown in 0.2 mM Cd2+. NH4+ significantly reduced the pectin and hemicellulose contents and inhibited the pectin methylesterase (PME) activity in rice roots, thereby reducing the negative charges in the cell wall and decreasing the accumulation of Cd2+ in roots. In addition, NH4+ reduced the absorption and root-to-shoot translocation of Cd2+ by decreasing the expression of OsHMA2 and OsNramp5 in the root. Levels of the signaling molecule putrescine were significantly higher in the roots of both rice cultivars provided with NH4+ compared with NO3-. The addition of putrescine reduced Cd2+ contents in both rice cultivars and increased the chlorophyll content in shoots by reducing root cell wall pectin and hemicellulose contents, inhibiting PME activity and suppressing the expression of OsHMA2 and OsNramp5 in the root. Taken together, these results indicate that NH4+ treatment alleviated Cd toxicity, enabling rice to withstand the noxious effects of Cd by modifying the cell wall Cd-binding capacity due to alterations of pectin and hemicellulose contents and Cd transport, processes induced by increasing putrescine levels. Our findings suggest methods to decrease Cd accumulation in rice by applying NH4+ fertilizers.

Ammonium uptake and metabolism alleviate PEG-induced water stress in rice seedlings.

Ammonium (NH4+) can enhance the water stress induced drought tolerance of rice seedlings in comparison to nitrate (NO3-) nutrition. To investigate the mechanism involved in nitrogen (N) uptake, N metabolism and transcript abundance of associated genes, a hydroponic experiment was conducted in which different N sources were supplied to seedlings growing under water stress. Compared to nitrate, ammonium prevented water stress-induced biomass, leaf SPAD and photosynthesis reduction to a significantly larger extent. Water stress significantly increased root nitrate reductase (NR) and nitrite reductase (NiR) activities, but decreased leaf NiR and glutamate synthetase (GS) activities under NO3- supply, causing lower nitrate content in roots and higher in leaves. In contrast, under NH4+ supply root GS and glutamine oxoglutarate aminotransferase (GOGAT) activities were significantly decreased under water stress, but remained higher in leaves, compared to NO3- treatment, which was beneficial for the transport and assimilation of ammonium in leaves. 15N tracing assays demonstrated that rice 15N uptake rate and accumulation were significant reduced under water stress, but were higher in plants supplied with NH4+ than with NO3-. Therefore, the formers showed higher leaf soluble sugar, proline and amino acids contents, and in turn, associated with a higher photosynthesis rate and biomass accumulation. Most genes related to NO3- uptake and reduction in roots and leaves were down-regulated; however, two ammonium transporter genes closely related to NH4+ uptake (AMT1;2 and AMT1;3) were up-regulated in response to water stress. Overall, our findings suggest that ammonium supply alleviated waters tress in rice seedlings, mainly by increasing root NH4+ uptake and leaf N metabolism.