Activities Of Metabolism-related Enzymes Research Articles

Development and evaluation of a precision heat treatment device for delaying postharvest softening of muskmelon

To extend the limited commercial storage of muskmelons due to insufficient shelf life, a heat treatment device with precise temperature control was designed and applied to three muskmelon varieties: "Xizhou Mi 25" (XZM), "Jinmi 3" (JM), and "Jiashi" (JS). The effectiveness of this device and the effect of heat treatment on the softening of muskmelons during storage were evaluated. The results indicated no significant difference between the temperatures set by the control system and the actual measured temperatures (p > 0.05), demonstrating the high accuracy of the temperature control system. After optimization of the heat treatment device, no thermal damage was observed in the heat-treated group of muskmelons. The energy consumption of the heat treatment device was only half that of the insulated tank. By the 18th day of storage, the protopectin (PP) content in the heat-treated group was significantly lower than in the control group. Correlation analysis showed that hardness was positively correlated with PP content and negatively correlated with water-soluble pectin (WSP). Additionally, cell wall metabolism-related enzyme activities were negatively correlated with PP content. These results indicated that the heat treatment effectively delayed muskmelon softening during postharvest storage. This study provides technical support for the industrial application of heat treatment devices in muskmelon preservation.

Comparison of behavioral responses, respiratory metabolism-related enzyme activities, and metabolomics of the juvenile Chinese mitten crab Eriocheir sinensis with different tolerance to air exposure

Air exposure is a common stressor for Chinese mitten crab (Eriocheir sinensis) during rearing and transport, and air exposure tolerance can serve as a crucial indicator for assessing the quality of juvenile E. sinensis. In this study, juvenile E. sinensis were divided into two groups based on their behavioral responses: Group S, which exhibited strong tolerance to air exposure, and Group W, which exhibited weak tolerance. Immersed crabs, not exposed to air, served as a control group (Group C). Whole body morphological characteristics and enzyme activities related to respiratory metabolism in the hemolymph and anterior gills were compared among the three groups. Non-targeted LC-MS metabolomic analysis was conducted on anterior gills. The results showed that, independent of developmental stage, crabs that were larger and had higher condition factor were more tolerant to air exposure. Additionally, compared to Group W, air exposure had a relatively small effect on glycolysis and anaerobic respiratory metabolic processes in the hemolymph and anterior gills of Group S. In response to air exposure, E. sinensis experienced increased energy demand, and switched from aerobic to anaerobic respiration to increase energy supply. Simultaneously, air exposure induced oxidative stress in the hemolymph and anterior gills. This study enhances our understanding of the response mechanism of E. sinensis to air exposure and provides a theoretical reference for the identification of high-quality juvenile E. sinensis.

The Combined Application of Urea and Fulvic Acid Regulates Apple Tree Carbon and Nitrogen Metabolism and Improves Anthocyanin Biosynthesis

Improving apple peel color has been an important objective in apple production. To better understand the effect and mechanism of the combined application of urea and FA (fulvic acid) regulation of anthocyanin biosynthesis, a field experiment was performed in 2022 and 2023, respectively, under five treatments of urea + FA (CK, urea only; FA50, urea + 50 kg ha−1 FA; FA100, urea + 100 kg ha−1 FA; FA150, urea + 150 kg ha−1 FA; FA200, urea + 200 kg ha−1 FA), using isotope (13C and 15N) marking to analyze the changes in carbon (C) and nitrogen (N) nutrient distribution as well as anthocyanin biosynthesis in fruits. We observed that, under FA application conditions, anthocyanin content in the peel was elevated in both years, with increases of 15.98~52.88% in 2022 and 15.93~52.94% in 2023. The best promotion effects were observed under FA150 treatment. Apart from the expression levels of anthocyanin biosynthesis-related genes and transcription factors in the apple peel, this positive effect on anthocyanin content induced by FA addition was also found to be associated with the optimization of C and N distribution in leaves and fruits. On the one hand, the application of FA not only enhanced leaf photosynthetic-related indexes (such as Pn, Gs, and Rubisco activity) and influenced (increased) S6PDH, SPS, and SS activities in leaves, but also elevated fruit sugar metabolism-related enzyme (SDH, SS-c, AI, and NI) activity and upregulated fruit stalk sugar transporter (MdSOT1, MdSOT3, MdSUT1 and MdSUT4) gene expression, which ultimately promoted the synthesis and the leaf to fruit transport of photosynthates, thus promoting 13C-photosynthate accumulation in fruits. On the other hand, FA application elevated leaves’ N metabolism-related enzyme (GS and GOGAT) activity and optimized 15N distribution in leaves and fruits. Moreover, we also observed that FA application altered the fate of N fertilizer in apple orchards, showed an elevation in apple tree 15NUE and soil 15N residuals and showed a decrease in soil 15N loss. In summary, the appropriate application of FA150 (urea + 150 kg ha−1) synergistically optimized C and N nutrient distribution, and promoted anthocyanin biosynthesis in apple trees.

Repeated marine heatwaves aggravate the adverse effects of nano-TiO2 on physiological metabolism of the thick-shelled mussel Mytilus coruscus

Global climate change is a major trigger of unexpected temperature fluctuations. The impacts of marine heatwaves (MHWs) and nano-titanium dioxide (nano-TiO2) on marine organisms have been extensively investigated. However, the potential mechanisms underlying their interactive effects on physiological processes and metabolism remain poorly understood, especially regarding periodic MHWs in real-world conditions. In this study, the effects of nano-TiO2 (at concentrations of 0, 25, and 250 μg/L) and periodic MHWs on the condition index (CI) and underlying metabolic mechanisms were investigated in mussels (Mytilus coruscus). The results showed that mussels try to upregulate their respiration rate (RR) to enhance aerobic metabolism (indicated by elevated succinate dehydrogenase) under short-term nano-TiO2 exposure. However, even at ambient concentration (25 μg/L), prolonged nano-TiO2 exposure inhibited ingestion ability (decreased clearance rate) and glycolysis (inhibited pyruvate kinase, hexokinase, and phosphofructokinase activities), which led to an insufficient energy supply (decreased triglyceride, albumin, and ATP contents). Repeated thermal scenarios caused more severe physiological damage, demonstrating that mussels are fragile to periodic MHWs. MHWs decreased the zeta potential of the nano-TiO2 particles but increased the hydrodynamic diameter. Additionally, exposure to nano-TiO2 and periodic MHWs further affected aerobic respiration (inhibited lactate dehydrogenase and succinate dehydrogenase activities), metabolism (decreased RR, activities of respiratory metabolism-related enzymes, and expressions of PEPCK, PPARγ, and ACO), and overall health condition (decreased ATP and CI). These findings indicate that the combined stress of these two stressors exerts more detrimental impact on the physiological performance and energy metabolism of mussels, and periodic MHWs exacerbate the toxicological effects of ambient concentration nano-TiO2. Given the potential worsening of nanoparticle pollution and the increase in extreme heat events in the future, the well-being of mussels in the marine environment may face further threats.

Optimization of cultivation system for Bacillus Siamese strain and its biocontrol effect on postharvest Colletotrichum gloeosporioides

In this study, we established an effective cultivation system for Bacillus Siamese (N-1), identified key antibacterial substances, and explored the underlying mechanisms of optimized N-1 fermentation for controlling pathogens. Our results demonstrate that the optimized system significantly enhanced the inhibitory effect of N-1 on five types of pathogens affecting tropical fruits. Additionally, non-targeted metabolomics analysis and ultra-high performance liquid chromatography triple quadrupole mass spectrometer system (UPLC-MS/MS) revealed the presence of lipopeptides, including Surfactin and FengycinA, in the optimized fermentation. Furthermore, in vitro experiments indicated that lipopeptide treatment (LT) at a concentration of 3.125 mg mL−1 significantly distorted the hyphae, decreased the activity of antioxidant enzymes, increased the levels of reactive oxygen species (ROS), malondialdehyde (MDA) and hydrogen peroxide (H2O2) contents, and enhanced protein exosmosis rate of C. gloeosporioides. Moreover, LT markedly reduced the activities of energy metabolism-related enzymes, including succinate dehydrogenase (SDH), Na+K+-ATPase, and Ca2+Mg2+-ATPase, as well as ATP content, leading to apoptosis of C. gloeosporioides. In vivo experiments revealed that LT significantly inhibited the expansion of disease spots caused by C. gloeosporioides in mango fruit. These findings suggest that the established culture system could serve as a potential strategy to enhance biocontrol efficacy and prevent fruit decay.

Acute waterborne cadmium exposure induces liver ferroptosis in Channa argus

The impact of cadmium (Cd) toxicity on fish liver injury has received much attention in recent years. Currently, autophagy, apoptosis and endoplasmic reticulum stress were reported in Cd exposed fish liver, and if there are other mechanisms (such as ferroptosis) and relevant signaling pathways involved in fish remains unknown. An experiment was conducted to investigate Cd toxicity in Channa argus (Cantor, 1842) exposed to 0, 1.0, and 2.0 mg Cd/L of water for 96 h. Cd disrupted the structure of mitochondria in the liver. Besides, Cd induced ferroptosis by significantly increasing the level of Fe2+, ROS, MDA and significantly decreasing the level of Ferritin, GSH, GSH-Px, GPX4, GST and SOD (p < 0.05 in all cases). In addition, the mRNA expression of ferroptosis related genes, gpx4 and slc7a11, were significantly downregulated by Cd. Moreover, Cd exposure significantly inhibited the Nrf2/Keap1 signaling pathway, one of the pathways involved in ferroptosis, by upregulating the mRNA levels of keap1a and keap1b, and downregulating the mRNA levels of nrf2 and its target genes (ho-1, nqo1 and cat). Cd exposure also caused extensive accumulation of vacuoles and lipid droplets in liver, as well as an increase in triglyceride content. Cd significantly affected lipid metabolism related enzyme activity and gene expression, which were also regulated by Nrf2/Keap1 signaling pathway. In summary, these results indicate that ferroptosis is a mechanism in waterborne Cd exposed fish liver injury via the Nrf2/Keap1 signaling pathway and the Cd induced hepatic steatosis is also modulated by Nrf2/Keap1 pathway at the whole-body level in fish. These findings provide new insights into the fish liver injury and molecular basis of Cd toxicity.

Effects of fishing stress on fatty acid and amino acid composition and glycolipid metabolism in triploid rainbow trout

Triploid Oncorhynchus mykiss is an important economic fish worldwide. Fishing stress can affect its growth and meat quality. This study first explored the effects of fishing stress on fatty acid and amino acid in triploid O. mykiss. Results showed fishing stress significantly reduced the content of docosadienoic acid, Gly, Arg, and DAA (P < 0.05). Targeted lipidomics analysis furthered suggested that some lipid molecules belonging to TG, DG, PC, Cer, ChE, and So were significantly up-regulated; while some lipid molecules belonging to Cer, LPE, LPC, PS, PC, and SM were significantly down-regulated, suggesting an accelerated glycolipid metabolism. Eventually, the glycolipid metabolism-related enzyme activity and gene expressions were examined, and the results indicated that O. mykiss was anti-oxidative stress by affecting relevant glycolipid metabolism signaling pathways and participating in cellular redox homeostasis. Findings of this study provide a theoretical foundation for further investigation into the mechanisms through which fishing stress affects O. mykiss.

Melatonin Priming Promotes Crop Seed Germination and Seedling Establishment Under Flooding Stress by Mediating ABA, GA, and ROS Cascades.

Both seed germination and subsequent seedling establishment are key checkpoints during the life cycle of seed plants, yet flooding stress markedly inhibits both processes, leading to economic losses from agricultural production. Here, we report that melatonin (MT) seed priming treatment enhances the performance of seeds from several crops, including soybean, wheat, maize, and alfalfa, under flooding stress. Transcriptome analysis revealed that MT priming promotes seed germination and seedling establishment associated with changes in abscisic acid (ABA), gibberellin (GA), and reactive oxygen species (ROS) biosynthesis and signaling pathways. Real-time quantitative RT-PCR (qRT-PCR) analysis confirmed that MT priming increases the expression levels of GA biosynthesis genes, ABA catabolism genes, and ROS biosynthesis genes while decreasing the expression of positive ABA regulatory genes. Further, measurements of ABA and GA concentrations are consistent with these trends. Following MT priming, quantification of ROS metabolism-related enzyme activities and the concentrations of H2O2 and superoxide anions (O2 -) after MT priming were consistent with the results of transcriptome analysis and qRT-PCR. Finally, exogenous application of GA, fluridone (an ABA biosynthesis inhibitor), or H2O2 partially rescued the poor germination of non-primed seeds under flooding stress. Collectively, this study uncovers the application and molecular mechanisms underlying MT priming in modulating crop seed vigor under flooding stress.

Effect of exogenous silicon treatments on cell wall metabolism and textural properties of tomato fruits

This study investigated the effects of exogenous silicon (Si) treatment on cell wall metabolism in tomato fruits. The experiment was conducted with ‘Jinfan502’ tomato (Solanum lycopersicum L.) as the test material, which was cultivated in substrates with foliar sprays of the following different concentrations of Si treatments: 0 mmol·L−1 (CK), 0.6 mmol·L−1 (T1), 1.2 mmol·L−1 (T2), and 1.8 mmol·L−1 (T3). To study the effects of the treatment on the mature green, breaker, and red ripening stages of tomato fruit cell wall components, cell wall metabolism-related enzyme activities, textural properties, and the impact of ethylene production during the red ripening stage were assessed. The results showed that the cell wall components and textural properties of the T2 treatment were significantly higher than those of the CK treatment in the green mature, breaker, and red ripening stages. Among them, at the red ripening stage of fruiting, the content of cell wall components in the T2 treatment was significantly improved, and the contents of protopectin, cellulose, hemicellulose, and expansin were increased by 6.29 %, 10.04 %, 2.52 %, and 3.95 %, respectively, relative to the CK treatment; the firmness of the fruit was also significantly increased, by 13.23 %, compared with the CK treatment. Cell-wall-metabolism-related enzyme activity was significantly lower in the T2 treatment than in the CK treatment at the green mature, breaker, and red ripening stages. When Si (T2) was applied during the red ripening stage, the activities of cell wall metabolism-related enzymes were significantly inhibited; compared to the CK treatment, the activities of pectinase (PE), polygalacturonase (PG), pectin methylesterase (PME), β-galactosidase (β-Gal), lipoxygenase (LOX), pectin lyase (PL), and cellulase (CL) were reduced by 16.34 %, 19.37 %, 28.07 %, 10.73 %, 19.86 %, 8.47 %, and 6.53 %, respectively. Furthermore, the ethylene content of the red ripened fruits under the T2 treatment was significantly reduced by 21.59 % compared to the CK treatment. In addition, multiple sets of significant or extremely significant negative correlations existed among ethylene, cell wall components, and textural properties at red ripening stage. Finally, principal component analysis and hierarchical cluster analysis of cell-wall metabolism-related enzyme activities in the three stages of treatment with different Si concentrations showed that the models significantly separated the T2 treatment from the CK, T1, and T3 treatments. In conclusion, exogenous Si T2 treatment (1.2 mmol·L−1) had the greatest effect on delaying cell wall metabolism, which provides the theoretical and technical basis for the enhancement of storage and transport resistance in tomatoes.

Dietary lipid supplementation alleviated the impacts of polystyrene nanoplastic exposure in Litopenaeus vannamei

The widespread occurrence of nanoplastic (NP) pollution in the environment is a growing concern, and its presence poses a potential threat to cultured aquatic animals. Previously, we found that NPs can significantly affect the lipid metabolism of shrimp. However, relevant reports about the effects of increasing dietary lipid levels on NP toxicity are lacking. Therefore, we explored the effects of dietary supplementation with different lipid levels on the growth and lipid metabolism of Pacific white shrimp (Litopenaeus vannamei). We cultured L. vannamei at three dietary lipid levels (3 %, 6 %, and 9 %) and three NP concentrations (0, 1, and 3 mg/L) for 2 months. We evaluated the effects of lipid levels on growth indexes, hepatopancreas morphological structure, lipid metabolism-related enzyme activity, and gene expression of the shrimp. The results showed that as lipid intake increased, the survival rate, body weight growth rate, and hepatosomatic ratio of the shrimp increased while the feed conversion rate decreased. Additionally, the crude protein and crude lipid contents increased, whereas the moisture and ash contents did not change much. We found that the morphological structure of the hepatopancreas was seriously damaged in the 3 mg/L NPs and 3 % dietary lipid group. Finally, lipid metabolism-related enzyme activities and gene expression levels increased with increased dietary lipid levels. Together, these results suggest that increasing dietary lipid content can improve shrimp growth and alleviate lipid metabolism disorders caused by NPs. This study is the first to show that nutrition regulation can alleviate the toxicity of NPs, and it provides a theoretical basis for the green and healthy culture of L. vannamei.

Improving the Yield and Quality of Tomato by Using Organic Fertilizer and Silicon Compared to Reducing Chemical Nitrogen Fertilization

Essential macronutrient nitrogen (N) is crucial for plant growth and yield, but excessive chemical N fertilizer not only increases unnecessary production costs but also causes environmental pollution. Therefore, reducing N fertilizer use by increasing organic fertilizer use is crucial for sustainable agriculture. In this study, we investigated the effects of three nitrogen levels—the recommended rate (N), a 20.0% reduced rate (0.8N), and a 40.0% reduced rate (0.6N)—and two levels of organic fertilizer—a normal dose (M) and a four-times the normal dose (4M)—combined with root application of the beneficial element silicon (Si) on the photosynthetic characteristics, yield, and fruit quality of the tomato cultivar ‘Tianxi No. 5’. Compared with M + N treatment, the longitudinal diameter, transverse diameter, fruit weight, and fruit yield of tomato fruit in 4M + 0.6N treatment significantly increased by 12.4%, 14.6%, 14.5%, and 12.8%, respectively, while the yield was further improved with Si application. In addition, a reduction in N fertilizer and an increase in organic fertilizer, combined with Si application, improved fruit quality parameters such as concentrations of vitamin C, lycopene, phenols, flavonoids, sucrose, fructose, etc., and promoted sugar metabolism-related enzyme activity (sucrose synthase, invertase, and sucrose phosphate synthase) and the accumulation of N in the fruit. The principal component analysis and three-factor analysis of variance (ANOVA) of the fruit quality and yield indices showed that nitrogen fertilizer, organic fertilizer, silicon fertilizer, and the interaction of the three had significant effects on the quality and yield of tomato fruits, and that the 4M + 0.6N + Si treatment had the best combined effect on the yield and quality of the tomatoes. Thus, a moderate reduction in chemical N fertilizer, combined with increased organic fertilizer and Si, could be an effective agronomic practice for improving the yield and quality of tomatoes.

MdbZIP44–MdCPRF2-like–Mdα-GP2 regulate starch and sugar metabolism in apple under nitrogen supply

Abstract Nitrogen (N) is regarded as an essential macronutrient and is tightly associated with carbon (C) metabolism in plants. The transcriptome data obtained from this study showed that the expression level of the apple basic leucine zipper (bZIP) transcription factor (TF) MdbZIP44 was up-regulated in ‘Oregon Spur Delicious’ (Malus domestica Borkh.) apple fruits under nitrogen supply. MdbZIP44 bound to the promoter of Mdα-GP2 gene and inhibited its expression, thereby promoting starch accumulation and decreasing glucose content in apple and tomato fruits. Besides, overexpression of MdbZIP44 promoted sucrose accumulation by regulating the activities of sucrose metabolism-related enzymes and the expression of sugar metabolism-related genes in apple callus and tomato fruits. Furthermore, biochemical assays indicated that MdbZIP44 directly interacted with MdCPRF2-like, another bZIP gene in apple. Meanwhile, this study found that MdCPRF2-like, along with the MdbZIP44 and MdCPRF2-like complex, could activate the expression of Mdα-GP2, respectively. In conclusion, this study provides a new reference for potential mechanisms underlying that MdbZIP44–MdCPRF2-like–Mdα-GP2 regulates starch and sugar metabolism under nitrogen supply.

Rational Utilization of Sediment Resources Improves Rice Yield and Nitrogen Use Efficiency under Salt Stress

Soil salinization negatively affects rice growth and yield; however, how different sludge sources regulate rice growth and yield under salt stress was rarely investigated. This study evaluated the performance of two salt-tolerant rice cultivars, Chaoyou 1000 and Longliangyou 506, grown in two sediment sources, pond sediment (PS) and river sludge (RS), under salt stress (56 ds m−1 brine irrigation) with conventional soil (CS) used as the control. The results showed that the rice yield under the PS and RS treatments was enhanced by 51.0% and 43.6% as compared with CS, respectively, owing to an improvement in spikelet per panicle, 1000-grain weight, dry matter accumulation, and the chlorophyll content in both rice cultivars. Compared with CS, the total nitrogen accumulation, nitrogen grain production efficiency, nitrogen harvest index, and nitrogen partial productivity under the PS and RS treatments were increased by 18.9–28.9%, 17.0–20.6%, 7.2–16.6%, and 43.8–50.9%, respectively. Moreover, rice grown in PS and RS showed higher activities of nitrogen metabolism-related enzymes (nitrate reductase, glutamine synthetase, and glutamate synthetase) at the heading stage and higher K+ and K+/Na+ contents in the leaves. Overall, a balanced utilization of sediment resources (especially pond sediment) can effectively alleviate salt stress and improve the yield and nitrogen use efficiency in rice.

Influence of myoinositol on post-ripening and softening of Prunus salicina ‘Wushan plum’

To investigate the impact of myoinositol (MI) immersion treatment on the storage characteristics of Prunus salicina ‘Wushan Plum’, we assessed myoinositol content, ascorbic acid content, weight loss, decay rate, alteration in color, titratable acidity (TA), soluble solids (TSS), firmness, cell wall metabolism-related compounds, enzyme activities, and levels of gene expression throughout a 15-day storage period at 25 °C. The results revealed that MI treatment could increase myoinositol and ascorbic acid contents of fruit during the pre-storage period, effectively delay the color transformation and decay progression of P. salicina ‘Wushan Plum’ while maintaining elevated levels of TA and TSS. Furthermore, it suppressed the increase in weight loss and the decline in firmness. Notably, the delay in softening was more pronounced in the group treated with 100 mg L−1 MI compared to other groups. MI treatment regulated the expression levels of various genes associated with cell wall metabolism, which resulted in reduced activities of polygalacturonase (PG), pectate lyase (PL), pectin methylesterase (PME), cellulase (Cx), and β-glucosidase (β-Glu), and increased activities of phenylalanine ammonia-lyase (PAL) and cinnamyl alcohol dehydrogenase (CAD). Furthermore, MI treatment maintained higher levels of covalently bound pectin (CSP), cellulose, and lignin, while decreasing the levels of water-soluble pectin (WSP) in the fruit. As a result, MI treatment could delay the depolymerization of cell wall polysaccharides and further delay the quality deterioration of P. salicina ‘Wushan Plum’ fruits under ambient storage environment and prolong the storage period.

Nanomaterial-based regulation of redox metabolism for enhancing cancer therapy.

Altered redox metabolism is one of the hallmarks of tumor cells, which not only contributes to tumor proliferation, metastasis, and immune evasion, but also has great relevance to therapeutic resistance. Therefore, regulation of redox metabolism of tumor cells has been proposed as an attractive therapeutic strategy to inhibit tumor growth and reverse therapeutic resistance. In this respect, nanomedicines have exhibited significant therapeutic advantages as intensively reported in recent studies. In this review, we would like to summarize the latest advances in nanomaterial-assisted strategies for redox metabolic regulation therapy, with a focus on the regulation of redox metabolism-related metabolite levels, enzyme activity, and signaling pathways. In the end, future expectations and challenges of such emerging strategies have been discussed, hoping to enlighten and promote their further development for meeting the various demands of advanced cancer therapies. It is highly expected that these therapeutic strategies based on redox metabolism regulation will play a more important role in the field of nanomedicine.

Flavonoids from mulberry leaves inhibit fat production and improve fatty acid distribution in adipose tissue in finishing pigs

This study evaluated the effects of flavonoids from mulberry leaves (FML) on plasma biochemical indices, serum activities of lipid metabolism-related enzymes, fat morphology, fatty acid composition, and lipid metabolism in different adipose tissues of finishing pigs. We used 120 Chinese hybrid barrows of Berkshire and Bama mini-pigs with an average initial body weight of 45.11 ± 4.23 kg. The pigs were randomly assigned to five treatment groups and fed a control diet based on corn, soybean meal, and wheat bran or a control diet supplemented with 0.02%, 0.04%, 0.08%, or 0.16% FML. Each experimental group had six replicates (pens), with four pigs per pen. After a 7-d adaptation period, the feeding trial was conducted for 58 d. Blood and adipose tissue samples were collected from 30 pigs (one pig per pen) at the end of the test. The results showed that FML supplementation significantly decreased the feed intake to body gain ratio, the plasma concentrations of total cholesterol and free fatty acids, and the serum activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase (linear or quadratic effects, P < 0.05), and decreased the plasma triglyceride concentration (quadratic, P = 0.07). Increasing FML supplementation increased the average daily gain and serum activities of lipoprotein lipase (linear and quadratic effects, P < 0.05) and adipose triglyceride lipase (linear, P < 0.05). Dietary FML supplementation decreased the adipocyte area in the dorsal subcutaneous adipose (DSA) tissue of finishing pigs (linear, P = 0.05) and increased the adipocyte area in the visceral adipose tissue (quadratic, P < 0.01). Increasing FML supplementation decreased the C20:1 content in DSA, abdominal subcutaneous adipose, and visceral adipose tissues of finishing pigs (P < 0.05) and increased the C18:3n3 and n-3 PUFA contents (P < 0.05). The lipid metabolism genes were regulated by the PPARγ-LXRα-ABCA1 signaling pathway, and their expressions differed in different adipose tissues. These findings suggest that FML improved growth performance, regulated lipid metabolism, inhibited fat production, and improved fatty acid distribution in the adipose tissue of finishing pigs, thereby improving pig fat's nutritional quality and health value.

Effects of mepiquat chloride and plant population density on leaf photosynthesis and carbohydrate metabolism in upland cotton

BackgroundMepiquat chloride (MC) application and plant population density (PPD) increasing are required for modern cotton production. However, their interactive effects on leaf physiology and carbohydrate metabolism remain obscure. This study aimed to examine whether and how MC and PPD affect the leaf morpho-physiological characteristics, and thus final cotton yield. PPD of three levels (D1: 2.25 plants·m−2, D2: 4.5 plants·m−2, and D3: 6.75 plants·m−2) and MC dosage of two levels (MC0: 0 g·ha−2, MC1: 82.5 g·ha−2) were combined to create six treatments. The dynamics of nonstructual carbohydrate concentration, carbon metabolism-related enzyme activity, and photosynthetic attributes in cotton leaves were examined during reproductive growth in 2019 and 2020.ResultsAmong six treatments, the high PPD of 6.75 plants·m−2 combined with MC application (MC1D3) exhibited the greatest seed cotton yield and biological yield. The sucrose, hexose, starch, and total nonstructural carbohydrate (TNC) concentrations peaked at the first flowering (FF) stage and then declined to a minimum at the first boll opening (FBO) stage. Compared with other treatments, MC1D3 improved starch and TNC concentration by 5.4% ~ 88.4%, 7.8% ~ 52.0% in 2019, and by 14.6% ~ 55.9%, 13.5% ~ 39.7% in 2020 at the FF stage, respectively. Additionally, MC1D3 produced higher transformation rates of starch and TNC from the FF to FBO stages, indicating greater carbon production and utilization efficiency. MC1D3 displayed the maximal specific leaf weight (SLW) at the FBO stage, and the highest chlorophyll a (Chl a), Chl b, and Chl a + b concentration at the mid-late growth phase in both years. The Rubisco activity with MC1D3 was 2.6% ~ 53.2% higher at the flowering and boll setting stages in both years, and 2.4% ~ 52.7% higher at the FBO stage in 2020 than those in other treatments. These results provided a explanation of higher leaf senescence-resistant ability in MC1D3.ConclusionIncreasing PPD coupled with MC application improves cotton yield by enhancing leaf carbohydrate production and utilization efficiency and delaying leaf senescence.

Effects of Fulvic Acid on Growth and Nitrogen Utilization Efficiency in M9T337 Seedlings

Both fulvic acid (FA) and nitrogen (N) play important roles in agricultural production in China. Plants typically show a higher nitrogen utilization efficiency (NUE) under FA application. However, the role of FA application in apple growth and NUE remains unclear. A hydroponic culture experiment was performed, and M9T337 seedlings (a dwarf apple rootstock) were used as the experimental subjects. The biomass, photosynthesis, accumulation, and distribution of photosynthates, N absorption and assimilation, and relative gene expression in the seedlings were examined after treatment with five different concentrations of FA (0, 60, 120, 180, and 240 mg·L−1, represented by CK, FA1, FA2, FA3, FA4, respectively). The results showed that the seedling dry weight and 15NUE were enhanced by FA, and both were highest under the FA2 (the concentration of fulvic acid is 120 mg·L−1) treatment. Further analysis revealed that under the FA2 treatment, the root morphology was optimized, and the root activity was relatively high. Compared with CK (control, the concentration of fulvic acid is 0 mg·L−1), the FA2 treatment strengthened photosynthesis, elevated the key enzyme activities related to C metabolism, upregulated the gene expression of sugar transport proteins, and increased the root sorbitol and sucrose contents, which suggested that the FA2 treatment optimally affected the root growth and N absorption because it enhanced photosynthate synthesis and the leaf-to-root translocation of photoassimilates. The seedlings in the FA2 treatment group also showed a significantly higher NO3− influx rate and NRT (nitrate transporter) gene expression in the roots. Moreover, relatively high N metabolism-related enzyme activities in the leaves and roots were also observed under the FA2 treatment. The isotope labeling results showed that the optimal FA2 supply not only promoted seedling 15N absorption but also optimized the distribution of C and N in the seedlings. These results suggested that an optimal FA supply (120 mg·L−1) enhanced seedling NUE by strengthening photoassimilate synthesis and transport from leaves to roots, regulating N absorption, assimilation, and distribution.

Polystyrene nanoplastics induce lipid metabolism disorder and alter fatty acid composition in the hepatopancreas of Pacific whiteleg shrimp (Litopenaeus vannamei)

The impact of nanoplastics (NPs) on environmental pollution and aquatic organisms has gradually attracted attention, but there are relatively few reports of the effects of NPs on the lipid metabolism of crustaceans. In this study, we exposed Pacific whiteleg shrimp (Litopenaeus vannamei) to different concentrations of polystyrene NPs (0, 0.1, 1, 5, and 10 mg/L) for 28 days. We then evaluated the effects of NP exposure on metabolite content, histology, lipid metabolism-related enzyme activity, and gene expression. Our results showed that with increasing NPs concentrations and exposure time, (1) the crude protein and crude fat content decreased and fatty acid composition changed; (2) the tissue structure was destroyed and the number of lipid droplets increased in the hepatopancreas; (3) the activities of acetyl-CoA carboxylase, fatty acid synthase, carnitine palmitoyl transferase-1, pyruvate kinase and low-density lipoprotein content tended to decrease and that of lipase and high-density lipoprotein content first increased and then decreased; the content of triglycerides and total carbohydrate first decreased and then increased; (4) the expression of fatty acid synthesis-related genes (Fas, SREBP, and FAD), fatty acid transport-related genes (FATP, FABP, and ACBP), and fatty acid decomposition-related genes (Ampk and lip1) first increased and then decreased. These results indicate that exposure to NPs can cause physiological disorders of fat metabolism in L.vannamei and that high concentrations of NPs have a negative impact on lipid metabolism. These results of this study provide valuable ecotoxicological data for better interpretation of the mechanism of action of NPs in crustaceans.

Nitrogen limitation affects carbon and nitrogen metabolism in mung bean (Vigna radiata L.)

Studying the effects of nitrogen limitation on carbon, nitrogen metabolism, and nutrient uptake of mung bean is a scientific issue. In this study, urea (CO(NH2)2, 125 kg hm−2) was applied at the V2, V6, R1, R2, and R4 stages, respectively, to ensure sufficient N resources during the growth process of mung beans. This study found that nitrogen limitation inhibited mung bean photosynthesis and reduced photosynthetic efficiency, which was manifested by reducing Pn (net photosynthetic rate), Gs (stomatal conductance), Tr (transpiration rate), and Ci (intercellular carbon dioxide concentration). Second, nitrogen limitation reduced N metabolism-related enzyme activity, such as NR (nitrate reductase), GOGAT (glutamate synthase), and GDH (glutamate dehydrogenase), indicating that nitrogen limitation inhibited the process of nitrogen metabolism, reducing nitrogen assimilation. Meanwhile, topdressing N fertilizer can promote the P and K uptake, and improve the partial factor productivity of P and K, which suggests that nitrogen limitation reduced P and K use efficiency. In addition, this study found that Lvfeng5 responded more significantly to nitrogen fertilizers, and had higher nitrogen use efficiency or better adaptability compared with Lvfeng2. This study provided valuable insights into the physiological and metabolic responses of mung beans to nutrient deficiency.