Inhibition Of Transport Research Articles

Biosurfactant-affected mobility of oxytetracycline and its variations with surface chemical heterogeneity in saturated porous media

Herein, the influences of rhamnolipid (a typical biosurfactant) on oxytetracycline (OTC) transport in the porous media and their variations with the surface heterogeneities of the media (uncoated sand, goethite (Goe)-, and humic acid (HA)-coated sands) were explored. Compared to uncoated sand, goethite and HA coatings suppressed OTC mobility by increasing deposition sites. Interestingly, rhamnolipid-affected OTC transport strongly depended on the chemical heterogeneities of aquifers and biosurfactant concentrations. Concretely, adding rhamnolipid (1–3 mg/L) inhibited OTC mobility through sand columns because of the bridging effect of biosurfactant between sand and OTC. Unexpectedly, rhamnolipid of 10 mg/L did not further improve the inhibition of OTC transport owing to the fact that the deposition capacity of rhamnolipid reached its maximum. OTC mobility in Goe-coated sand columns was inhibited by 1 mg/L rhamnolipid. However, the inhibitory effect decreased with the increasing rhamnolipid concentration (3 mg/L) and exhibited a promoted effect at 10 mg/L rhamnolipid. This surprising observation was that the increased rhamnolipid molecules gradually occupied the favorable deposition sites (i.e., the positively charged sites). In comparison, rhamnolipid facilitated OTC transport in the HA-coated sand column. The promotion effects positively correlated with rhamnolipid concentrations because of the high electrostatic repulsion and deposition site competition induced by the deposited rhamnolipid. Another interesting phenomenon was that rhamnolipid's enhanced or inhibitory effects on OTC transport declined with the increasing solution pH because of the decreased rhamnolipid deposition on porous media surfaces. These findings benefit our understanding of the environmental behaviors of antibiotics in complex soil-water systems containing biosurfactants.

The net electrostatic potential and hydration of ABCG2 affect substrate transport

ABCG2 is a medically important ATP-binding cassette transporter with crucial roles in the absorption and distribution of chemically-diverse toxins and drugs, reducing the cellular accumulation of chemotherapeutic drugs to facilitate multidrug resistance in cancer. ABCG2’s capacity to transport both hydrophilic and hydrophobic compounds is not well understood. Here we assess the molecular basis for substrate discrimination by the binding pocket. Substitution of a phylogenetically-conserved polar residue, N436, to alanine in the binding pocket of human ABCG2 permits only hydrophobic substrate transport, revealing the unique role of N436 as a discriminator. Molecular dynamics simulations show that this alanine substitution alters the electrostatic potential of the binding pocket favoring hydration of the transport pore. This change affects the contact with substrates and inhibitors, abrogating hydrophilic compound transport while retaining the transport of hydrophobic compounds. The N436 residue is also required for optimal transport inhibition of ABCG2, as many inhibitors are functionally impaired by this ABCG2 mutation. Overall, these findings have biomedical implications, broadly extending our understanding of substrate and inhibitor interactions.

Salt-Stress-Induced Ion Transport Contributes to K+/Na+ Homeostasis in Roots of Ping’ou Hybrid Hazelnut

Soil salinity is a worldwide problem that adversely affects plant growth and development. Soil salinization in Xinjiang of China is very serious. Ping’ou hybrid hazelnut, as an important ecological and economic tree species, as well as a salt-tolerant plant, has been grown in Xinjiang for over 20 years. Understanding the salt-tolerance mechanism of Ping’ou hybrid hazelnut is of great significance for the breeding of salt-tolerant varieties and the rational utilization of salinized land. In this study, ‘Liaozhen 7’, a fine variety of Ping’ou hybrid hazelnut, was selected as test material, and seedlings were treated with 0 (control), 50, 100 and 200 mM NaCl. Subsequently, the pattern of NaCl-induced fluxes of Na+, K+ and H+ in the root meristematic zone and their response to ion transport inhibitors were studied using non-invasive micro-test technology (NMT). Different concentrations of NaCl stress significantly increased the Na+ concentration in roots, while K+ concentration decreased first and then increased with the increase of NaCl concentration. Meanwhile, NaCl stress induced a significant decline in K+/Na+ ratio. Control and 200 mM NaCl-induced Na+ and K+ fluxes in roots exhibited an outward efflux, whereas an inward flux was observed for H+. Under 200 mM NaCl stress, the average rates of net Na+ and K+ efflux, as well as H+ influx in roots were significantly increased, which were 11.6, 6.7 and 2.3 times higher than that of control, respectively. Furthermore, pharmacological experiments showed that 200 mM NaCl-induced Na+ efflux; H+ influx was significantly suppressed by amiloride, an inhibitor of plasma membrane (PM) Na+/H+ antiporter, and sodium vanadate, an inhibitor of PM H+-ATPase. Net Na+ efflux and H+ influx induced by NaCl decreased by 89.9% and 135.0%, respectively. The NaCl-induced Na+ efflux was mediated by a Na+/H+ antiporter using energy provided by PM H+-ATPase. The NaCl-induced K+ efflux was significantly restricted by tetraethylamine chloride, a K+ channel inhibitor, and promoted by sodium vanadate, which decreased by 111.2% and increased by 80.8%, respectively, indicating that K+ efflux was regulated by depolarization-activated outward-rectifying K+ channels and non-selective cation channels (NSCCs). In conclusion, NMT data revealed that NaCl stress up regulated the root Na+/H+ antiporter and H+ pump (an activity of PM Na+/H+ antiport system) of ‘Liaozhen 7’, which compelled the Na+/H+ exchange across the PM and restricted K+ loss via depolarization-activated K+ channels and NSCCs simultaneously, thereby maintaining the K+/Na+ homeostasis and higher salt tolerance.

Phytochrome B1/B2 and auxin transport are involved in the regulation of shoot: root ratio by far-red radiation in tomato

Plants possess a set of photoreceptors to perceive changes in the light spectrum. Phytochromes (PHY) B1/B2 sense changes in red: far red ratios and are involved in mediating the shade-avoidance responses (SAR) in tomato. Far red (FR) increases the fraction of dry mass partitioning to the shoot at the expense of the root in tomato, but the control of this response has not yet been explained. We studied the role of phytochromes and auxin transport in the regulation of shoot: root ratio. We hypothesized that a loss-of-function mutation in phyB1/B2 leads to a strong increase in shoot: root ratio, similar to the effect of reduced R: FR ratio in wildtype plants. We also hypothesized that the phyB1/B2 double mutation suppresses shoot: root ratio responses when exposed to a reduced R: FR ratio. Furthermore, we hypothesized that the increased shoot: root ratio is linked to the changes in auxin transport between shoot and root. To test these hypotheses, we conducted an experiment in a climate chamber where both wildtype and phyB1/B2 double mutant tomato plants (Solanum lycopersicum cv. Moneymaker) were grown for 21 days with 0, 55 or 85 μmol m−2 s−1 FR in a background of white + red LED light at 150 μmol m−2 s−1. On the 14th day, auxin polar transport inhibitor 1-N-naphthylphthalamic acid (NPA) was applied at the shoot-root junction. PhyB1/B2 mutants showed a higher shoot: root ratio than the wildtype plants. Both wildtype and phyB1/B2 mutants responded to FR with an increase in shoot: root ratio. Blocking auxin transport from shoot to root led to an increase in shoot: root ratio for both genotypes under all light conditions. These results suggest that, similar to other SAR responses like stem elongation, the response of shoot: root ratio to additional FR also involves the regulation by phytochromes, possibly via affecting auxin transport between shoot and root.

Structure, catalysis, chitin transport, and selective inhibition of chitin synthase

Chitin is one of the most abundant natural biopolymers and serves as a critical structural component of extracellular matrices, including fungal cell walls and insect exoskeletons. As a linear polymer of β-(1,4)-linked N-acetylglucosamine, chitin is synthesized by chitin synthases, which are recognized as targets for antifungal and anti-insect drugs. In this study, we determine seven different cryo-electron microscopy structures of a Saccharomyces cerevisiae chitin synthase in the absence and presence of glycosyl donor, acceptor, product, or peptidyl nucleoside inhibitors. Combined with functional analyses, these structures show how the donor and acceptor substrates bind in the active site, how substrate hydrolysis drives self-priming, how a chitin-conducting transmembrane channel opens, and how peptidyl nucleoside inhibitors inhibit chitin synthase. Our work provides a structural basis for understanding the function and inhibition of chitin synthase.

The identification of material basis of Si Miao Formula effective for attenuating non-alcoholic fatty liver disease

Ethnopharmacological relevanceThe Si Miao Formula (SMF), a traditional Chinese medicine, originated from the "Cheng Fang Bian Du" during the Qing Dynasty and is commonly employed for the treatment of gout and hyperuricemia. We have demonstrated the anti-NAFLD effect of SMF by regulating hepatic lipid metabolism in high fat and high sucrose (HFHS) feeding mice in our previous report. However, the material basis of SMF for its anti-NAFLD effect remains unknown. Aim of the studyTo compare the effeciacy of different components of SMF and identify the material basis for its anti-NAFLD effect. Materials and methodsIn the present study, a “Leave-one out” strategy was adopted by removing one herb from SMF each time, and the anti-NAFLD effects of four decomposed recipes containing three herbs were evaluated in C57BL/6J mice fed with an HFHS diet for 16 weeks. The chemical components of SMF and the absorbed entities in serum were assayed using UHPLC-Q-Exactive-Orbitrap HRMS. Finally, a new chemical combination with four compounds (berberine, betaine, caffeic acid, p-coumaric acid, 2:2:1:1) were generated (SMF component composition, SMF_CC), and its anti-NAFLD effect was evaluated by comparing with the original SMF in the mouse model. ResultsVarified effects on NAFLD mice were observed among the decomposed recipes of SMF, while the original SMF showed advantages over its decomposed recipes. A total of 111 chemicals were identified from SMF, and 21 of them were detected in serum after oral administration of SMF. Comparing to SMF, SMF_CC showed comparable anti-NAFLD effect in HFHS-diet-fed mice, which was associated with the inhibition of hepatic fatty acid synthesis and transport, as well as inflammation. ConclusionOur current results suggested that the original SMF was better than its decomposed recipes in NAFLD management, and the derived SMF_CC was also effective in inhibiting NAFLD formation, highlighting its potential of being a novel natural agent for NAFLD therapy.

LIPID TRANSFER PROTEIN4 regulates cotton ceramide content and activates fiber cell elongation.

Cell elongation is a fundamental process for plant growth and development. Studies have shown lipid metabolism plays important role in cell elongation; however, the related functional mechanisms remain largely unknown. Here, we report that cotton (Gossypium hirsutum) LIPID TRANSFER PROTEIN4 (GhLTP4) promotes fiber cell elongation via elevating ceramides (Cers) content and activating auxin-responsive pathways. GhLTP4 was preferentially expressed in elongating fibers. Over-expression and down-regulation of GhLTP4 led to longer and shorter fiber cells, respectively. Cers were greatly enriched in GhLTP4-overexpressing lines and decreased dramatically in GhLTP4 down-regulating lines. Moreover, auxin content and transcript levels of indole-3-acetic acid (IAA)-responsive genes were significantly increased in GhLTP4-overexpressing cotton fibers. Exogenous application of Cers promoted fiber elongation, while NPA (N-1-naphthalic acid, a polar auxin transport inhibitor) counteracted the promoting effect, suggesting that IAA functions downstream of Cers in regulating fiber elongation. Furthermore, we identified a basic helix-loop-helix transcription factor, GhbHLH105, that binds to the E-box element in the GhLTP4 promoter region and promotes the expression of GhLTP4. Suppression of GhbHLH105 in cotton reduced the transcripts level of GhLTP4, resulting in smaller cotton bolls and decreased fiber length. These results provide insights into the complex interactions between lipids and auxin-signaling pathways to promote plant cell elongation.

Apical Dominance and Branching in Plantlets of Colt Cherry Lines Expressing Different Light and Auxin Signalling Sensitivities

The establishment of plant architecture requires coordination of distinct processes including shoot branching and apical dominance (AD). AD involves the bud apical shoot, mainly through indole-3-acetic acid (IAA) synthetized by the cells of the meristem and young leaves. The rootward flow generates an auxin gradient in the stem and buds, regulating lateral bud (LB) outgrowth. Phytochromes and AD are involved in the shade-avoidance syndrome in woody plants. However, the underlying mechanisms remain poorly understood. The aim of this study was to evaluate the sensitivity of cherry rootstocks to light, mediated by the photoreceptor phytochrome, and its effect on the role of auxin in driving branching by AD. Pharmacological treatments using transport inhibitors and a competitor of IAA were applied to transgenic lines of Colt cherry rootstock, which showed different sensitivities to light because of the ectopic expression of a rice phyA gene. Results showed different physiological behaviours among the transgenic lines and between themselves and the Colt-wt line. Exogenous IBA inhibited Colt-wt LB outgrowth, and this inhibition was less intense in transgenic lines. The IAA-inhibitors and IAA-competitor promoted branching. In in vitro phyA-transgenic plantlets, the ectopic gene induced greater branching and a higher number of buds developed in new shoots. This work confirms a positive action of phytochrome on lateral branching in cherry rootstock, playing a role in the regulation of AD. Moreover, we suggest that the confined in vitro system might now be used as a phenotyping screening to test the plasticity of the response, highlighting the behaviour of modified genotypes due to an ectopic insertion event by simple and rapid procedures.

Impact of mercury on photosynthetic performance of Lemna minor: a chlorophyll fluorescence analysis

The purpose of this study was to evaluate the effectiveness of chlorophyll fluorescence analysis in detecting the effects of mercury (Hg) treatment in duckweed species Lemna minor. The results showed that Hg treatment (ranging from 0.0 to 0.4 µM) significantly impacted the plant's photosynthetic ability, with a decrease in variable chlorophyll fluorescence, energy fluxes, density of reaction centers, and performance index. Complete inhibition of electron transport was observed in plants treated with high Hg concentrations, and the quantum yield of primary photochemistry and the ratio of dissipated energy to absorption both decreased with increasing Hg concentrations. Performance Index (PI) was significantly affected by the Hg concentrations, reaching zero in plants treated with the highest Hg concentration. Overall, JIP analysis was found to be an effective tool for detecting deleterious effects of Hg in plants.

SuperNatural inhibitors to reverse multidrug resistance emerged by ABCB1 transporter: Database mining, lipid-mediated molecular dynamics, and pharmacokinetics study.

An effective approach to reverse multidrug resistance (MDR) is P-glycoprotein (P-gp, ABCB1) transport inhibition. To identify such molecular regulators, the SuperNatural II database, which comprises > 326,000 compounds, was virtually screened for ABCB1 transporter inhibitors. The Lipinski rule was utilized to initially screen the SuperNatural II database, identifying 128,126 compounds. Those natural compounds were docked against the ABCB1 transporter, and those with docking scores less than zosuquidar (ZQU) inhibitor were subjected to molecular dynamics (MD) simulations. Based on MM-GBA binding energy (ΔGbinding) estimations, UMHSN00009999 and UMHSN00097206 demonstrated ΔGbinding values of -68.3 and -64.1 kcal/mol, respectively, compared to ZQU with a ΔGbinding value of -49.8 kcal/mol. For an investigation of stability, structural and energetic analyses for UMHSN00009999- and UMHSN00097206-ABCB1 complexes were performed and proved the high steadiness of these complexes throughout 100 ns MD simulations. Pharmacokinetic properties of the identified compounds were also predicted. To mimic the physiological conditions, MD simulations in POPC membrane surroundings were applied to the UMHSN00009999- and UMHSN00097206-ABCB1 complexes. These results demonstrated that UMHSN00009999 and UMHSN00097206 are promising ABCB1 inhibitors for reversing MDR in cancer and warrant additional in-vitro/in-vivo studies.

Evolutionarily divergent mTOR remodels translatome for tissue regeneration.

An outstanding mystery in biology is why some species, such as the axolotl, can regenerate tissues whereas mammals cannot1. Here, we demonstrate that rapid activation of protein synthesis is a unique feature of the injury response critical for limb regeneration in the axolotl (Ambystoma mexicanum). By applying polysome sequencing, we identify hundreds of transcripts, including antioxidants and ribosome components that are selectively activated at the level of translation from pre-existing messenger RNAs in response to injury. By contrast, protein synthesis is not activated in response to non-regenerative digit amputation in the mouse. We identify the mTORC1 pathway as a key upstream signal that mediates tissue regeneration and translational control in the axolotl. We discover unique expansions in mTOR protein sequence among urodele amphibians. By engineering an axolotl mTOR (axmTOR) in human cells, we show that these changes create a hypersensitive kinase that allows axolotls to maintain this pathway in a highly labile state primed for rapid activation. This change renders axolotl mTOR more sensitive to nutrient sensing, and inhibition of amino acid transport is sufficient to inhibit tissue regeneration. Together, these findings highlight the unanticipated impact of the translatome on orchestrating the early steps of wound healing in ahighly regenerative species and provide a missing link in our understanding of vertebrate regenerative potential.

Genetic diversity and genome-wide association study of 13 agronomic traits in 977 Beta vulgaris L. germplasms

BackgroundSugar beet (Beta vulgaris L.) is an economically essential sugar crop worldwide. Its agronomic traits are highly diverse and phenotypically plastic, influencing taproot yield and quality. The National Beet Medium-term Gene Bank in China maintains more than 1700 beet germplasms with diverse countries of origin. However, it lacks detailed genetic background associated with morphological variability and diversity.ResultsHere, a comprehensive genome-wide association study (GWAS) of 13 agronomic traits was conducted in a panel of 977 sugar beet accessions. Almost all phenotypic traits exhibited wide genetic diversity and high coefficient of variation (CV). A total of 170,750 high-quality single-nucleotide polymorphisms (SNPs) were obtained using the genotyping-by-sequencing (GBS). Neighbour-joining phylogenetic analysis, principal component analysis, population structure and kinship showed no obvious relationships among these genotypes based on subgroups or regional sources. GWAS was carried out using a mixed linear model, and 159 significant associations were detected for these traits. Within the 25 kb linkage disequilibrium decay of the associated markers, NRT1/PTR FAMILY 6.3 (BVRB_5g097760); nudix hydrolase 15 (BVRB_8g182070) and TRANSPORT INHIBITOR RESPONSE 1 (BVRB_8g181550); transcription factor MYB77 (BVRB_2g023500); and ethylene-responsive transcription factor ERF014 (BVRB_1g000090) were predicted to be strongly associated with the taproot traits of root groove depth (RGD); root shape (RS); crown size (CS); and flesh colour (FC), respectively. For the aboveground traits, UDP-glycosyltransferase 79B6 (BVRB_9g223780) and NAC domain-containing protein 7 (BVRB_5g097990); F-box protein At1g10780 (BVRB_6g140760); phosphate transporter PHO1 (BVRB_3g048660); F-box protein CPR1 (BVRB_8g181140); and transcription factor MYB77 (BVRB_2g023500) and alcohol acyltransferase 9 (BVRB_2g023460) might be associated with the hypocotyl colour (HC); plant type (PT); petiole length (PL); cotyledon size (C); and fascicled leaf type (FLT) of sugar beet, respectively. AP-2 complex subunit mu (BVRB_5g106130), trihelix transcription factor ASIL2 (BVRB_2g041790) and late embryogenesis abundant protein 18 (BVRB_5g106150) might be involved in pollen quantity (PQ) variation. The candidate genes extensively participated in hormone response, nitrogen and phosphorus transportation, secondary metabolism, fertilization and embryo maturation.ConclusionsThe genetic basis of agronomical traits is complicated in heterozygous diploid sugar beet. The putative valuable genes found in this study will help further elucidate the molecular mechanism of each phenotypic trait for beet breeding.

Targeting Pulmonary Fibrosis by SLC1A5-Dependent Glutamine Transport Blockade.

The neutral amino acid glutamine plays a central role in TGF-β (transforming growth factor-β)-induced myofibroblast activation and differentiation. Cells take up glutamine mainly through a transporter expressed on the cell surface known as solute carrier SLC1A5 (solute carrier transporter 1A5). In the present work, we demonstrated that profibrotic actions of TGF-β are mediated, at least in part, through a metabolic maladaptation of SLC1A5 and that targeting SLC1A5 abrogates multiple facets of fibroblast activation. This approach could thus represent a novel therapeutic strategy to treat patients with fibroproliferative diseases. We found that SLC1A5 was highly expressed in fibrotic lung fibroblasts and fibroblasts isolated from idiopathic pulmonary fibrosis lungs. The expression of profibrotic targets, cell migration, and anchorage-independent growth by TGF-β required the activity of SLC1A5. Loss or inhibition of SLC1A5 function enhanced fibroblast susceptibility to autophagy; suppressed mTOR, HIF (hypoxia-inducible factor), and Myc signaling; and impaired mitochondrial function, ATP production, and glycolysis. Pharmacological inhibition of SLC1A5 by the small-molecule inhibitor V-9302 shifted fibroblast transcriptional profiles from profibrotic to fibrosis resolving and attenuated fibrosis in a bleomycin-treated mouse model of lung fibrosis. This is the first study, to our knowledge, to demonstrate the utility of a pharmacological inhibitor of glutamine transport in fibrosis, providing a framework for new paradigm-shifting therapies targeting cellular metabolism for this devastating disease.

Expression of CsSCL1 and Rooting Response in Chestnut Leaves Are Dependent on the Auxin Polar Transport and the Ontogenetic Origin of the Tissues.

The mechanisms underlying the de novo regeneration of adventitious roots are still poorly understood, particularly in trees. We developed a system for studying adventitious rooting (AR) at physiological and molecular levels using leaves excised from chestnut microshoots of the same genotype but with two distinct ontogenetic origins that differ in rooting competence. Leaves were treated with auxin and N-1-naphthyl-phthalamic acid (NPA), an inhibitor of auxin polar transport (PAT). The physiological effects were investigated by recording rooting rates and the number and quality of the roots. Molecular responses were examined by localizing and monitoring the changes in the expression of CsSCL1, an auxin-inducible gene in juvenile and mature shoots during AR. The rooting response of leaves was ontogenetic-stage dependent and similar to that of the donor microshoots. Initiation of root primordia and root development were inhibited by application of NPA, although its effect depended on the timing of application. CsSCL1 was upregulated by auxin only in rooting-competent leaves during the novo root organogenesis, and the expression was reduced by NPA. The inhibitory effect on gene expression was detected during the reprograming of rooting competent cells towards root initials in response to auxin, indicating that PAT-mediated upregulation of CsSCL1 is required in the initial steps of AR in chestnut leaves. The localized expression of CsSCL1 in the quiescent center (QC) also suggests a role for this gene in the maintenance of meristematic competence and root radial patterning.

Synergistic Inhibitory Effect of Quercetin and Cyanidin-3O-Sophoroside on ABCB1.

The human ABCB1 (P-glycoprotein, Pgp) protein is an active exporter expressed in the plasma membrane of cells forming biological barriers. In accordance with its broad substrate spectrum and tissue expression pattern, it affects the pharmacokinetics of numerous chemotherapeutic drugs and it is involved in unwanted drug-drug interactions leading to side effects or toxicities. When expressed in tumor tissues, it contributes to the development of chemotherapy resistance in malignancies. Therefore, the understanding of the molecular details of the ligand-ABCB1 interactions is of crucial importance. In a previous study, we found that quercetin (QUR) hampers both the transport and ATPase activity of ABCB1, while cyandin-3O-sophroside (C3S) stimulates the ATPase activity and causes only a weak inhibition of substrate transport. In the current study, when QUR and C3S were applied together, both a stronger ATPase inhibition and a robust decrease in substrate transport were observed, supporting their synergistic ABCB1 inhibitory effect. Similar to cyclosporine A, a potent ABCB1 inhibitor, co-treatment with QUR and C3S shifted the conformational equilibrium to the "inward-facing" conformer of ABCB1, as it was detected by the conformation-selective UIC2 mAb. To gain deeper insight into the molecular details of ligand-ABCB1 interactions, molecular docking experiments and MD simulations were also carried out. Our in silico studies support that QUR and C3S can bind simultaneously to ABCB1. The most favourable ligand-ABCB1 interaction is obtained when C3S binds to the central substrate binding site and QUR occupies the "access tunnel". Our results also highlight that the strong ABCB1 inhibitory effect of the combined treatment with QUR and C3S may be exploited in chemotherapy protocols for the treatment of multidrug-resistant tumors or for improving drug delivery through pharmacological barriers.

Tale of cAMP as a second messenger in auxin signaling and beyond.

The 3',5'-cyclic adenosine monophosphate (cAMP) is a versatile second messenger in many mammalian signaling pathways. However, its role in plants remains not well-recognized. Recent discovery of adenylate cyclase (AC) activity for transport inhibitor response 1/auxin-signaling F-box proteins (TIR1/AFB) auxin receptors and the demonstration of its importance for canonical auxin signaling put plant cAMP research back into spotlight. This insight briefly summarizes the well-established cAMP signaling pathways in mammalian cells and describes the turbulent and controversial history of plant cAMP research highlighting the major progress and the unresolved points. We also briefly review the current paradigm of auxin signaling to provide a background for the discussion on the AC activity of TIR1/AFB auxin receptors and its potential role in transcriptional auxin signaling as well as impact of these discoveries on plant cAMP research in general.

Isolation and Identification of Herbicidal Active Compounds from Brassica oleracea L. and Exploration of the Binding Sites of Brassicanate A Sulfoxide.

Brassica oleracea L. has strong allelopathic effects on weeds. However, the allelochemicals with herbicidal activity in B. oleracea L. are still unknown. In this study, we evaluated the activity of allelochemicals isolated from Brassica oleracea L. based on the germination and growth of model plant Lactuca sativa Linn., grass weed Panicum miliaceum, and broadleaf weed Chenopodium album. Additionally, we employed molecular docking to predict the binding of brassicanate A sulfoxide to herbicide targets. The results of this study showed that eight compounds with herbicidal activity were isolated from B. oleracea L., and the predicted results indicated that brassicanate A sulfoxide was stably bound to dihydroxyacid dehydratase, hydroxymethylpyruvate dioxygenase, acetolactate synthase, PYL family proteins and transport inhibitor response 1. This research provides compound sources and a theoretical foundation for the development of natural herbicides.

Regulation of cholesterol metabolism during high fatty acid–induced lipid deposition in calf hepatocytes

Cholesterol in the circulation is partly driven by changes in feed intake, but aspects of cholesterol metabolism during development of fatty liver are not well known. The objective of this study was to investigate mechanisms of cholesterol metabolism in calf hepatocytes challenged with high concentrations of fatty acids (FA). To address mechanistic insights regarding cholesterol metabolism, liver samples were collected from healthy control dairy cows (n = 6; 7-13 d in milk) and cows with fatty liver (n = 6; 7-11 d in milk). In vitro, hepatocytes isolated from 3 healthy female calves (1 d old) were challenged with or without a mix of 1.2 mM FA to induce metabolic stress. In addition, hepatocytes were processed with 10 µmol/L of the cholesterol synthesis inhibitor simvastatin or 6 µmol/L of the cholesterol intracellular transport inhibitor U18666A with or without the 1.2 mM FA mix. To evaluate the role of cholesterol addition, hepatocytes were treated with 0.147 mg/mL methyl-β-cyclodextrin (MβCD + FA) or 0.147 mg/mL MβCD with or without 10 and 100 µmol/L cholesterol before incubation with FA (CHO10 + FA and CHO100 + FA). In vivo data from liver biopsies were analyzed by 2-tailed unpaired Student's t-test. Data from in vitro calf hepatocytes were analyzed by one-way ANOVA. Compared with healthy cows, blood plasma total cholesterol and plasma low-density lipoprotein cholesterol content in cows with fatty liver was markedly lower, whereas the hepatic total cholesterol content did not differ. In contrast, compared with healthy controls, the triacylglycerol content in the liver and the content of FA, β-hydroxybutyrate, and aspartate aminotransferase in the plasma of cows with fatty liver were greater. The results revealed that both fatty liver in vivo and challenge of calf hepatocytes with 1.2 mM FA in vitro led to greater mRNA and protein abundance of sterol regulatory element binding transcription factor 1 (SREBF1) and fatty acid synthase (FASN). In contrast, mRNA and protein abundance of sterol regulatory element binding transcription factor 2 (SREBF2), acyl coenzyme A-cholesterol acyltransferase, and ATP-binding cassette subfamily A member 1 (ABCA1) were lower. Compared with the FA group, the cholesterol synthesis inhibitor simvastatin led to greater protein abundance of microsomal triglyceride transfer protein and mRNA abundance of SREBF2, 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), ACAT2, and lower ABCA1 and FASN protein abundance. In contrast, compared with the FA group, the cholesterol intracellular transport inhibitor U18666A + FA led to greater total cholesterol concentration and greater protein and mRNA abundance of FASN. Compared with the MβCD + FA group, the addition of 10 µmol/L cholesterol led to greater concentration of cholesteryl ester and excretion of apolipoprotein B100, and greater protein and mRNA abundance of ABCA1 and microsomal triglyceride transfer protein, and lower concentration of malondialdehyde. Overall, a reduction in cholesterol synthesis promoted FA metabolism in hepatocytes likely to relieve the oxidative stress caused by the high FA load. The data suggest that maintenance of normal cholesterol synthesis promotes very low-density lipoprotein excretion and can reduce lipid accumulation and oxidative stress in dairy cows that experience fatty liver.

Improvement of the thermoelectric performance of boron-doped silicon by blocking minority carrier diffusion on the p+/p interface

Abstract A two-layer bulk Si material with different boron concentrations was prepared using spark plasma sintering to improve its thermoelectric performance by blocking minority carrier diffusion across its interfaces. The sintered two-layer sample (p+/p-Si) was cut to include the interface. Two monolayer samples (p+-Si, p-Si) were prepared for comparison. Seebeck coefficient mapping of the p+/p-Si surface by thermal probing confirmed a Seebeck coefficient gap between the two p-type Si layers, indicating that a band offset exists at the interface. When compared with the average resistivities and voltages for p+-Si and p-Si, the electrical resistivity in the p+/p-Si sample is almost identical, but the thermoelectric voltage is higher when the p+-part is heated more than the p-part. This indicates that bipolar carrier transport inhibition in the band offset improved the thermoelectric voltage. This bandgap engineering process and principle can be extended to other thermoelectric materials that can be processed via powder sintering.

VPT-like genes modulate Rhizobium-legume symbiosis and phosphorus adaptation.

Although vacuolar phosphate transporters (VPTs) are essential for plant phosphorus adaptation, their role in Rhizobium-legume symbiosis is unclear. In this study, homologous genes of VPT1 (MtVPTs) were identified in Medicago truncatula to assess their roles in Rhizobium-legume symbiosis and phosphorus adaptation. MtVPT2 and MtVPT3 mainly positively responded to low and high phosphate, respectively. However, both mtvpt2 and mtvpt3 mutants displayed shoot phenotypes with high phosphate sensitivity and low phosphate tolerance. The root-to-shoot phosphate transfer efficiency was significantly enhanced in mtvpt3 but weakened in mtvpt2, accompanied by lower and higher root cytosolic inorganic phosphate (Pi) concentration, respectively. Low phosphate induced MtVPT2 and MtVPT3 expressions in nodules. MtVPT2 and MtVPT3 mutations markedly reduced the nodule number and nitrogenase activity under different phosphate conditions. Cytosolic Pi concentration in nodules was significantly lower in mtvpt2 and mtvpt3 than in the wildtype, especially in tissues near the base of nodules, probably due to inhibition of long-distance Pi transport and cytosolic Pi supply. Also, mtvpt2 and mtvpt3 could not maintain a stable cytosolic Pi level in the nodule fixation zone as the wildtype under low phosphate stress. These findings show that MtVPT2 andMtVPT3 modulate phosphorus adaptation and rhizobia-legume symbiosis, possibly by regulating long-distance Pi transport.