Monolayer Borophene Formation on Cu(111) Surface Triggered by ⟨ 1 1 ¯ 0 ⟩ $\langle {1\bar{1}0} \rangle $ Step Edge.

Borophene, a promising material with potential applications in electronics, energy storage, and sensors, is successfully grown as a monolayer on Ag(111), Cu(111), and Au(111) surfaces using molecular beam epitaxy. The growth of two-dimensional borophene on Ag(111) and Au(111) is proposed to occur via surface adsorption and boron segregation, respectively. However, the growth mode of borophene on Cu(111) remains unclear. To elucidate this, scanning tunneling microscopy in conjunction with theoretical calculations is used to study the phase transformation of boron nanostructures under post-annealing treatments. Results show that by elevating the substrate temperature, boron nanostructures undergo an evolution from amorphous boron to striped-phase borophene (η = 1/6) adhering to the Cu ⟨ 1 1 ¯ 0 ⟩ $\langle {1\bar{1}0} \rangle $ step edge, and finally to irregularly shaped ß-type borophene (η = 5/36) either on the substrate surface or embedded in the topmost Cu layer. dI/dV spectra recorded near the borophene/Cu lateral interfaces indicate that the striped-phase borophene is a metastable phase, requiring more buckling and electron transfer to stabilize the crystal structure. These findings offer not only an in-depth comprehension of the ß-type borophene formation on Cu(111), but also hold potential for enabling borophene synthesis on weakly-binding semiconducting or insulating substrates with 1D active defects.

Improving fourth harmonic generation performance by elevating the operation temperature of ADP crystal.

In current inertial confinement fusion (ICF) facilities, potassium dihydrogen phosphate (KH2PO4, KDP) type crystals are the only nonlinear optical (NLO) materials that can satisfy the aperture requirement of the ICF laser driver. Ammonium dihydrogen phosphate (NH4H2PO4, ADP) crystal is a typical isomer of KDP crystal, with a large nonlinear optical coefficient, high ultraviolet transmittance, and large growth sizes, which is an important deep ultraviolet (UV) NLO material. In this paper, we investigated the effect of ADP temperature on its fourth-harmonic-generation (FHG) performance. When the temperature of the ADP crystal was elevated to 48.9 °C, the 90° phase-matched FHG of the 1064 nm laser was realized. Compared with the 79° phase-matched FHG at room temperature (23.0 °C), the output energy at 266 nm, conversion efficiency, angular acceptance, and laser-induced damage threshold (LIDT) increased 113%, 71%, 623%, 19.6%, respectively. It shows that elevating ADP temperature is an efficient method to improve its deep UV frequency conversion properties, which may also be available to other NLO crystals. This discovery provides a very valuable technology for the future development of UV, deep UV lasers in ICF facilities.

Broadband and ascendant nonlinear optical properties of the wide bandgap material GaN nanowires.

Gallium nitride (GaN) nanowire, as a type of wide bandgap nanomaterial, has attracted considerable interest because of its outstanding physicochemical properties and applications in energy storage and photoelectric devices. In this study, we prepared GaN nanowires via a facile chemical vapor deposition method and investigated their nonlinear absorption responses ranging from ultraviolet to near-infrared in the z-scan technology under irradiation by picosecond laser pulses. The experiment revealed that GaN nanowires exhibit remarkable nonlinear absorption characteristics attributed to their wide bandgap and nanostructure, including saturable absorption and reverse saturable absorption. When compared to bulk GaN crystals, the nanowires provide a richer and more potent set of nonlinear optical effects. Furthermore, we conducted an analysis of the corresponding electronic transition processes associated with photon absorption. Under high peak power density laser excitation, two-photon absorption or three-photon absorption dominate, with maximum modulation depths of 73.6%, 74.9%, 63.1% and 64.3% at 266 nm, 355 nm, 532 nm, and 1064 nm, respectively, corresponding to absorption coefficients of 0.22 cm/GW, 0.28 cm/GW, 0.08 cm/GW, and 2.82 ×10-4 cm3/GW2. At lower peak energy densities, GaN nanowires demonstrate rare and excellent saturation absorption characteristics at wavelength of 355 nm due to interband transitions, while saturable absorption is also observed at 532 nm and 1064 nm due to band tail absorption. The modulation depths are 85.2%, 41.9%, and 13.7% for 355 nm, 532 nm, and 1064 nm, corresponding to saturation intensities of 3.39 GW/cm2, 5.58 GW/cm2 and 14.13 GW/cm2. This indicates that GaN nanowires can be utilized as broadband optical limiters and high-performance pulse laser modulating devices, particularly for scarce ultraviolet optical limiters, and saturable absorbers for ultraviolet and visible lasers. Furthermore, our study demonstrates the application potential of wide bandgap nanomaterials in nonlinear optical devices.

Phospholipase D Mediates Glutamine-Induced mTORC1 Activation to Promote Porcine Intestinal Epithelial Cell Proliferation.

BACKGROUND: The intestinal epithelium is one of the fastest self-renewal tissues in the body, and glutamine plays a crucial role in providing carbon and nitrogen for biosynthesis. In intestinal homeostasis, phosphorylation-mediated signaling networks that cause altered cell proliferation, differentiation, and metabolic regulation have been observed. However, our understanding of how glutamine affects protein phosphorylation in the intestinal epithelium is limited, and identifying the essential signaling pathways involved in regulating intestinal epithelial cell growth is particularly challenging. OBJECTIVES: This study aimed to identify the essential proteins and signaling pathways involved in glutamine's promotion of porcine intestinal epithelial cell proliferation. METHODS: Phosphoproteomics was applied to describe the protein phosphorylation landscape under glutamine treatment. Kinase-substrate enrichment analysis was subjected to predict kinase activity and validated by qRT-PCR and Western blotting. Cell Counting Kit-8, glutamine rescue experiment, chloroquine treatment, and 5-fluoro-2-indolyl deschlorohalopemide inhibition assay revealed the possible underlying mechanism of glutamine promoting porcine intestinal epithelial cell proliferation. RESULTS: In this study, glutamine starvation was found to significantly suppress the proliferation of intestinal epithelial cells and change phosphoproteomic profiles with 575 downregulated sites and 321 upregulated sites. Interestingly, phosphorylation of eukaryotic initiation factor 4E-binding protein 1 at position Threonine70 was decreased, which is a crucial downstream of the mechanistic target of rapamycin complex 1 (mTORC1) pathway. Further studies showed that glutamine supplementation rescued cell proliferation and mTORC1 activity, dependent on lysosomal function and phospholipase D activation. CONCLUSION: In conclusion, glutamine activates mTORC1 signaling dependent on phospholipase D and a functional lysosome to promote intestinal epithelial cell proliferation. This discovery provides new insight into regulating the homeostasis of the intestinal epithelium, particularly in pig production.

Oxygen evolution reaction (OER) active sites in BiVO4 studied using density functional theory and XPS experiments.

Bismuth vanadate (BiVO4/BVO) has been widely studied as a photocatalytic water splitting semiconductor material in recent years because of its many advantages, such as its ease of synthesis and suitable band gap (2.4 eV). However, BVO still has some disadvantages, one of which is the low photocatalytic water oxidation activity. It is intriguing and unexpected to note that in the current literature, Bi atoms are taken as the oxygen evolution reaction (OER) active sites, while V metal atoms are not investigated in the OER, and the underlying reason for this remains unknown. In this work, using density functional theory (DFT) calculations and ab initio molecular dynamics simulations, we found that in BVO, the VO4 tetrahedron structure is very stable and there is strong surface reconstruction that leads to the V atoms on the surface having the same coordinates as in the bulk. For some high index surfaces, there are some theoretically predicted unsaturated V sites, but it is very easy to form a VO4 tetrahedron structure again by taking oxygen atoms from water. The other intermediates of OER are difficult to adsorb or desorb on this VO4 structure, which makes the V sites in BVO unsuitable as OER active sites. This VO4 structure remained stable during the molecular dynamics simulation at 300 and 673 K. The XPS characterization of various BVO morphologies validates our primary findings from DFT and molecular dynamics simulations. It reveals the presence of unsaturated Bi sites on the BVO surface, while unsaturated V sites are not observed. This study provides novel insights into the enhancement of OER activity of BVO and offers a fundamental understanding of OER activity in other photocatalysts containing V atoms.

Piceatannol Alleviates Deoxynivalenol-Induced Damage in Intestinal Epithelial Cells via Inhibition of the NF-κB Pathway.

Deoxynivalenol (DON) is a common mycotoxin that is widely found in various foods and feeds, posing a potential threat to human and animal health. This study aimed to investigate the protective effect of the natural polyphenol piceatannol (PIC) against DON-induced damage in porcine intestinal epithelial cells (IPEC-J2 cells) and the underlying mechanism. The results showed that PIC promotes IPEC-J2 cell proliferation in a dose-dependent manner. Moreover, it not only significantly relieved DON-induced decreases in cell viability and proliferation but also reduced intracellular reactive oxygen species (ROS) production. Further studies demonstrated that PIC alleviated DON-induced oxidative stress damage by increasing the protein expression levels of the antioxidant factors NAD(P)H quinone oxidoreductase-1 (NQO1) and glutamate-cysteine ligase modifier subunit (GCLM), and the mRNA expression of catalase (CAT), Superoxide Dismutase 1 (SOD1), peroxiredoxin 3 (PRX3), and glutathione S-transferase alpha 4 (GSTα4). In addition, PIC inhibited the activation of the nuclear factor-B (NF-κB) pathway, downregulated the mRNA expression of interleukin-1ß (IL-1ß), interleukin-6 (IL-6), and tumor necrosis factor α (TNF-α) to attenuate DON-induced inflammatory responses, and further mitigated DON-induced cellular intestinal barrier injury by regulating the protein expression of Occludin. These findings indicated that PIC had a significant protective effect against DON-induced damage. This study provides more understanding to support PIC as a feed additive for pig production.

Valtrate, an iridoid compound in Valeriana, elicits anti-glioblastoma activity through inhibition of the PDGFRA/MEK/ERK signaling pathway.

BACKGROUND: Valtrate, a natural compound isolated from the root of Valeriana, exhibits antitumor activity in many cancers through different mechanisms. However, its efficacy for the treatment of glioblastoma (GBM), a tumor type with a poor prognosis, has not yet been rigorously investigated. METHODS: GBM cell lines were treated with valtrate and CCK-8, colony formation and EdU assays, flow cytometry, and transwell, 3D tumor spheroid invasion and GBM-brain organoid co-culture invasion assays were performed to assess properties of proliferation, viability, apoptosis and invasion/migration. RNA sequencing analysis on valtrate-treated cells was performed to identify putative target genes underlying the antitumor activity of the drug in GBM cells. Western blot analysis, immunofluorescence and immunohistochemistry were performed to evaluate protein levels in valtrate-treated cell lines and in samples obtained from orthotopic xenografts. A specific activator of extracellular signal-regulated kinase (ERK) was used to identify the pathways mediating the effect. RESULTS: Valtrate significantly inhibited the proliferation of GBM cells in vitro by inducing mitochondrial apoptosis and suppressed invasion and migration of GBM cells by inhibiting levels of proteins associated with epithelial mesenchymal transition (EMT). RNA sequencing analysis of valtrate-treated GBM cells revealed platelet-derived growth factor receptor A (PDGFRA) as a potential target downregulated by the drug. Analysis of PDGFRA protein and downstream mediators demonstrated that valtrate inhibited PDGFRA/MEK/ERK signaling. Finally, treatment of tumor-bearing nude mice with valtrate led to decreased tumor volume (fivefold difference at day 28) and enhanced survival (day 27 vs day 36, control vs valtrate-treated) relative to controls. CONCLUSIONS: Taken together, our study demonstrated that the natural product valtrate elicits antitumor activity in GBM cells through targeting PDGFRA and thus provides a candidate therapeutic compound for the treatment of GBM.

SLC25A32 promotes malignant progression of glioblastoma by activating PI3K-AKT signaling pathway.

BACKGROUND: Solute carrier family 25 member 32 (SLC25A32) is an important member of SLC25A family and plays a role in folate transport metabolism. However, the mechanism and function of SLC25A32 in the progression of human glioblastoma (GBM) remain unclear. METHODS: In this study, folate related gene analysis was performed to explore gene expression profiles in low-grade glioma (LGG) and GBM. Western blotting, real-time quantitative PCR (qRT-PCR), and immunohistochemistry (IHC) were used to confirm the expression levels of SLC25A32 in GBM tissues and cell lines. CCK-8 assays, colony formation assays, and Edu assays were performed to assess the role of SLC25A32 on proliferation in GBM in vitro. A 3D sphere invasion assay and an ex vivo co-culture invasion model were performed to assess the effects of SLC25A32 on invasion in GBM. RESULTS: Elevated expression of SLC25A32 was observed in GBM, and high SLC25A32 expression was associated with a high glioma grade and poorer prognosis. Immunohistochemistry performed with anti-SLC25A32 on samples from an independent cohort of patients confirmed these results. Knockdown of SLC25A32 inhibited the proliferation and invasion of GBM cells, but overexpression of SLC25A32 significantly promoted cell growth and invasion. These effects were mainly due to the activation of the PI3K-AKT-mTOR signaling pathway. CONCLUSION: Our study demonstrated that SLC25A32 plays a significant role in promoting the malignant phenotype of GBM. Therefore, SLC25A32 can be used as an independent prognostic factor in patients with GBM, providing a new target for the comprehensive treatment of GBM.

Patient-centred care and patient autonomy: doctors' views in Chinese hospitals.

BACKGROUND: Patient-centred care and patient autonomy is one of the key factors to better quality of service provision, hence patient outcomes. It enables the development of patients' trusts which is an important element to a better doctor-patient relationship. Given the increasing number of patient disputes and conflicts between patients and doctors in Chinese public hospital, it is timely to ensure patient-centred care is fully and successfully implemented. However, limited studies have examined the views and practice in different aspects of patient-centred care among doctors in the Chinese public hospitals. METHODS: A quantitative approach was adopted by distributing paper-based questionnaires to doctors and patients in two hospitals (Level III and Level II) in Jinan, Shandong province, China. RESULTS: In total, 614 doctors from the surgical and internal medicine units of the two hospitals participated in the survey yielding 90% response rates. The study confirmed the inconsistent views among doctors in terms of their perception and practice in various aspects patient-centred care and patient autonomy regardless of the hospital where they work (category II or category III), their unit speciality (surgical or non-surgical), their gender or seniority. The high proportion of doctors (more than 20%) who did not perceive the importance of patient consultation prior to determining diagnostic and treatment procedure is alarming. This in in part due to the belief held by more than half of the doctors that patients were unable to make rational decisions and their involvement in treatment planning process did not necessarily lead to better treatment outcomes. CONCLUSION: The study calls for the development of system level policy and organisation wide strategies in encouraging and enabling the practice of patient-centred care and patient autonomy with the purposes of improving the quality of the service provided to patients by Chinese hospitals.

Adsorption of Pb(II) cation from aqueous solutions by acid modified low-rank coal: An experimental study and simulation.

An acid modified approach to enhance the adsorption capacity of low-rank coal (lignite) is proposed to reduce the risk of heavy metal ions within the wastewater. Adsorption kinetics, adsorption thermodynamics, adsorption coefficient and density functional theory DFT calculations were studied in this paper, respectively. The results indicate that the adsorption capacity of lignite was enlarged after HNO3 modification, and pseudo-second order kinetics model and Langmuir isothermal adsorption model can be used to describe the adsorption process. The surface chemical properties of lignite play a dominant role rather than the specific surface area and total pore volume in the Pb(II) cation adsorption process, and it is suggested that the adsorption of Pb(II) cation by raw lignite (RL) and modified lignite (ML) is mainly completed by chemical adsorption. The Fourier transform infrared spectroscopy (FTIR) characterization showed that the surface oxygen functional groups of lignite increased after modification. The results of interaction energies between the model molecule and Pb(II) cation show that Pb(II) cation and -C-O-C are most easily combined, followed by -COOH, and -C = O is the weakest.

Superconductivity in a Hole-Doped Mott-Insulating Triangular Adatom Layer on a Silicon Surface.

Adsorption of one-third monolayer of Sn on an atomically clean Si(111) substrate produces a two-dimensional triangular adatom lattice with one unpaired electron per site. This dilute adatom reconstruction is an antiferromagnetic Mott insulator; however, the system can be modulation doped and metallized using heavily doped p-type Si(111) substrates. Here, we show that the hole-doped dilute adatom layer on a degenerately doped p-type Si(111) wafer is superconducting with a critical temperature of 4.7±0.3 K. While a phonon-mediated coupling scenario would be consistent with the observed T_{c}, Mott correlations in the Sn-derived dangling-bond surface state could suppress the s-wave pairing channel. The latter suggests that the superconductivity in this triangular adatom lattice may be unconventional.

Doctors in Chinese public hospitals: demonstration of their professional identities.

BACKGROUND: An increase in the number of medical disputes and violence against doctors indicates a lack of trust in the medical profession by society in Chinese public hospitals. Empirical evidence confirms that one cause is the lack of professional identity demonstrated by doctors. Medical professionals are required to maintain high standards of competence and moral responsibility, and demonstrate qualities such as respect, compassion, integrity, responsiveness to needs, and commitment to sound ethical practice in order to maintain professional privilege. These principles and appropriate professional conduct are the foundation of the professional identity of the medical profession. METHODS: A quantitative approach was adopted by distributing paper-based questionnaires to doctors and patients in two hospitals (Level III and Level II) in Jinan, Shandong province, China. FINDINGS: In total, 614 doctors and 1184 inpatients on discharge from the surgical and internal medicine units of the two hospitals participated in the survey yielding 90% response rates. The study confirmed the variation amongst doctors in demonstrating their professionalism in terms of respecting patients' views and preferences when determining diagnostic procedures and treatment plans, and when making ethical decisions. Although 90% patients indicated that they showed respects to doctors, close to 20% of the doctors disagreed that they received high respect from patients. About 12% of doctors prescribed unnecessary diagnostic procedures to patient for the purpose of generating profit and more than 20% of patients indicated that they gave gifts to doctors in order to receive better treatment. CONCLUSIONS: Although about 80% of doctors demonstrated certain aspects of professionalism required by practitioners, the inconsistency across the medical workforce may exacerbate tense doctor-patient relationships. A review of medical curricula and focus of the internship program is required in order to assist medical graduates with forming required professional identity in order to improve patient satisfaction and better clinical outcomes. To be effective, a more systematic approach is recommended.

Recent Progress of Fiber-Optic Sensors for the Structural Health Monitoring of Civil Infrastructure.

In recent years, with the development of materials science and architectural art, ensuring the safety of modern buildings is the top priority while they are developing toward higher, lighter, and more unique trends. Structural health monitoring (SHM) is currently an extremely effective and vital safeguard measure. Because of the fiber-optic sensor's (FOS) inherent distinctive advantages (such as small size, lightweight, immunity to electromagnetic interference (EMI) and corrosion, and embedding capability), a significant number of innovative sensing systems have been exploited in the civil engineering for SHM used in projects (including buildings, bridges, tunnels, etc.). The purpose of this review article is devoted to presenting a summary of the basic principles of various fiber-optic sensors, classification and principles of FOS, typical and functional fiber-optic sensors (FOSs), and the practical application status of the FOS technology in SHM of civil infrastructure.

Evaluation method for the measuring comprehensive suitability of chelating agents: a study of the temporal dynamics of heavy metal activation.

The effects of chelating agents on heavy metal activation in Cd- and Pb-contaminated soils were studied through a dynamic activation experiment. An evaluation method for the measuring comprehensive suitability of chelating agent was established by calculating indexes for the degree of activation effect suitability and activated heavy metals' half-life suitability. The following results were obtained: in Cd- and Pb-contaminated soils, heavy metal activation effects reached or approached maximum activating effects within 1 d and subsequently showed different levels of decline in all chelating agent treatment conditions. Declines in activation effects similarly subjected to the law of exponents over time and to the goodness of fit in DTPA, NTA, and GLDA ranged from 0.80 to 0.98. For Cd- and Pb-contaminated soils, chelating agents' levels of comprehensive suitability (H) were recorded as follows: NTA(1.40) > GLDA(1.31) > DTPA(1.14) > EDTA(1.00) > EDDS(0.14) > CA(0.06) and GLDA(1.56) > DTPA(1.48) > EDTA(1.00) > NTA(0.78) > EDDS(0.26) > CA (0.02). GLDA and DTPA are both suitable for Cd and Pb phytoextraction. Moreover, NTA and GLDA are optimal chelating agents for Cd and Pb phytoextraction, respectively.

Vanadium Dioxide: The Multistimuli Responsive Material and Its Applications.

The reversible, ultrafast, and multistimuli responsive phase transition of vanadium dioxide (VO2 ) makes it an intriguing "smart" material. Its crystallographic transition from the monoclinic to tetragonal phases can be triggered by diverse stimuli including optical, thermal, electrical, electrochemical, mechanical, or magnetic perturbations. Consequently, the development of high-performance smart devices based on VO2 grows rapidly. This review systematically summarizes VO2 -based emerging technologies by classifying different stimuli (inputs) with their corresponding responses (outputs) including consideration of the mechanisms at play. The potential applications of such devices are vast and include switches, memories, photodetectors, actuators, smart windows, camouflages, passive radiators, resonators, sensors, field effect transistors, magnetic refrigeration, and oscillators. Finally, the challenges of integrating VO2 into smart devices are discussed and future developments in this area are considered.

Changes in the allocation of endogenous strigolactone improve plant biomass production on phosphate-poor soils.

Strigolactones (SLs) are carotenoid-derived phytohormones shaping plant architecture and inducing the symbiosis with endomycorrhizal fungi. In Petunia hybrida, SL transport within the plant and towards the rhizosphere is driven by the ABCG-class protein PDR1. PDR1 expression is regulated by phytohormones and by the soil phosphate abundance, and thus SL transport integrates plant development with nutrient conditions. We overexpressed PDR1 (PDR1 OE) to investigate whether increased endogenous SL transport is sufficient to improve plant nutrition and productivity. Phosphorus quantification and nondestructive X-ray computed tomography were applied. Morphological and gene expression changes were quantified at cellular and whole tissue levels via time-lapse microscopy and quantitative PCR. PDR1 OE significantly enhanced phosphate uptake and plant biomass production on phosphate-poor soils. PDR1 OE plants showed increased lateral root formation, extended root hair elongation, faster mycorrhization and reduced leaf senescence. PDR1 overexpression allowed considerable SL biosynthesis by releasing SL biosynthetic genes from an SL-dependent negative feedback. The increased endogenous SL transport/biosynthesis in PDR1 OE plants is a powerful tool to improve plant growth on phosphate-poor soils. We propose PDR1 as an as yet unexplored trait to be investigated for crop production. The overexpression of PDR1 is a valuable strategy to investigate SL functions and transport routes.

Effects and mechanistic aspects of absorbing organic compounds by coking coal.

Coal is a porous medium and natural absorbent. It can be used for its original purpose after adsorbing organic compounds, its value does not reduce and the pollutants are recycled, and then through systemic circulation of coking wastewater zero emissions can be achieved. Thus, a novel method of industrial organic wastewater treatment using adsorption on coal is introduced. Coking coal was used as an adsorbent in batch adsorption experiments. The quinoline, indole, pyridine and phenol removal efficiencies of coal adsorption were investigated. In addition, several operating parameters which impact removal efficiency such as coking coal consumption, oscillation contact time, initial concentration and pH value were also investigated. The coking coal exhibited properties well-suited for organics' adsorption. The experimental data were fitted to Langmuir and Freundlich isotherms as well as Temkin and Redlich-Peterson (R-P) models. The Freundlich isotherm model provided reasonable models of the adsorption process. Furthermore, the purification mechanism of organic compounds' adsorption on coking coal was analysed.

The importance of strigolactone transport regulation for symbiotic signaling and shoot branching.

MAIN CONCLUSION: This review presents the role of strigolactone transport in regulating plant root and shoot architecture, plant-fungal symbiosis and the crosstalk with several phytohormone pathways. The authors, based on their data and recently published results, suggest that long-distance, as well local strigolactone transport might occur in a cell-to-cell manner rather than via the xylem stream. Strigolactones (SLs) are recently characterized carotenoid-derived phytohormones. They play multiple roles in plant architecture and, once exuded from roots to soil, in plant-rhizosphere interactions. Above ground SLs regulate plant developmental processes, such as lateral bud outgrowth, internode elongation and stem secondary growth. Below ground, SLs are involved in lateral root initiation, main root elongation and the establishment of the plant-fungal symbiosis known as mycorrhiza. Much has been discovered on players and patterns of SL biosynthesis and signaling and shown to be largely conserved among different plant species, however little is known about SL distribution in plants and its transport from the root to the soil. At present, the only characterized SL transporters are the ABCG protein PLEIOTROPIC DRUG RESISTANCE 1 from Petunia axillaris (PDR1) and, in less detail, its close homologue from Nicotiana tabacum PLEIOTROPIC DRUG RESISTANCE 6 (PDR6). PDR1 is a plasma membrane-localized SL cellular exporter, expressed in root cortex and shoot axils. Its expression level is regulated by its own substrate, but also by the phytohormone auxin, soil nutrient conditions (mainly phosphate availability) and mycorrhization levels. Hence, PDR1 integrates information from nutrient availability and hormonal signaling, thus synchronizing plant growth with nutrient uptake. In this review we discuss the effects of PDR1 de-regulation on plant development and mycorrhization, the possible cross-talk between SLs and other phytohormone transporters and finally the need for SL transporters in different plant species.

Petunia hybrida PDR2 is involved in herbivore defense by controlling steroidal contents in trichomes.

As a first line of defense against insect herbivores many plants store high concentrations of toxic and deterrent secondary metabolites in glandular trichomes. Plant Pleiotropic Drug Resistance (PDR)-type ABC transporters are known secondary metabolite transporters, and several have been implicated in pathogen or herbivore defense. Here, we report on Petunia hybrida PhPDR2 as a major contributor to trichome-related chemical defense. PhPDR2 was found to localize to the plasma membrane and be predominantly expressed in multicellular glandular trichomes of leaves and stems. Down-regulation of PhPDR2 via RNA interference (pdr2) resulted in a markedly higher susceptibility of the transgenic plants to the generalist foliage feeder Spodoptera littoralis. Untargeted screening of pdr2 trichome metabolite contents showed a significant decrease in petuniasterone and petuniolide content, compounds, which had previously been shown to act as potent toxins against various insects. Our findings suggest that PhPDR2 plays a leading role in controlling petuniasterone levels in leaves and trichomes of petunia, thus contributing to herbivory resistance.

Molecular identification and functional analysis of a maize (Zea mays) DUR3 homolog that transports urea with high affinity.

MAIN CONCLUSION: Successful molecular cloning and functional characterization of a high-affinity urea permease ZmDUR3 provide convincing evidence of ZmDUR3 roles in root urea acquisition and internal urea-N-remobilization of maize plants. Urea occurs ubiquitously in both soils and plants. Being a major form of nitrogen fertilizer, large applications of urea assist cereals in approaching their genetic yield potential, but due to the low nitrogen-use efficiency of crops, this practice poses a severe threat to the environment through their hypertrophication. To date, except for paddy rice, little is known about the biological basis for urea movement in dryland crops. Here, we report the molecular and physiological characterization of a maize urea transporter, ZmDUR3. We show using gene prediction, PCR-based cloning and yeast complementation, that a functional full-length cDNA encoding a 731 amino acids-containing protein with putative 15 transmembrane α-helixes for ZmDUR3 was successfully cloned. Root-influx studies using (15)N-urea demonstrated ZmDUR3 catalyzes urea transport with a K m at ~9 µM when expressed in the Arabidopsis dur3-mutant. qPCR analysis revealed that ZmDUR3 mRNA in roots was significantly upregulated by nitrogen depletion and repressed by reprovision of nitrogen after nitrogen starvation, indicating that ZmDUR3 is a nitrogen-responsive gene and relevant to plant nitrogen nutrition. Moreover, detection of higher urea levels in senescent leaves and obvious occurrence of ZmDUR3 transcripts in phloem-cells of mature/aged leaves strongly implies a role for ZmDUR3 in urea vascular loading. Significantly, expression of ZmDUR3 complemented atdur3-mutant of Arabidopsis, improving plant growth on low urea and increasing urea acquisition. As it also targets to the plasma membrane, our data suggest that ZmDUR3 functions as an active urea permease playing physiological roles in effective urea uptake and nitrogen remobilization in maize.