Exogenous Brassinosteroid Facilitates Xylem Development in Pinus massoniana Seedlings

Brassinosteroids (BRs) are known to be essential regulators for wood formation in herbaceous plants and poplar, but their roles in secondary growth and xylem development are still not well-defined, especially in pines. Here, we treated Pinus massoniana seedlings with different concentrations of exogenous BRs, and assayed the effects on plant growth, xylem development, endogenous phytohormone contents and gene expression within stems. Application of exogenous BR resulted in improving development of xylem more than phloem, and promoting xylem development in a dosage-dependent manner in a certain concentration rage. Endogenous hormone determination showed that BR may interact with other phytohormones in regulating xylem development. RNA-seq analysis revealed that some conventional phenylpropanoid biosynthesis- or lignin synthesis-related genes were downregulated, but the lignin content was elevated, suggesting that new lignin synthesis pathways or other cell wall components should be activated by BR treatment in P. massoniana. The results presented here reveal the foundational role of BRs in regulating plant secondary growth, and provide the basis for understanding molecular mechanisms of xylem development in P. massoniana.     

Identification of MicroRNA 395a in 24-Epibrassinolide-Regulated Root Growth of Arabidopsis thaliana Using MicroRNA Arrays

Brassinosteroids (BRs) are endogenous plant hormones and are essential for normal plant growth and development. MicroRNAs (miRNAs) of Arabidopsis thaliana are involved in mediating cell proliferation in leaves, stress tolerance, and root development. The specifics of BR mechanisms involving miRNAs are unknown. Using customized miRNA array analysis, we identified miRNAs from A. thaliana ecotype Columbia (Col-0) regulated by 24-epibrassinolide (EBR, a highly active BR). We found that miR395a was significantly up-regulated by EBR treatment and validated its expression under these conditions. miR395a was over expressed in leaf veins and root tissues in EBR-treated miR395a promoter::GUS plants. We integrated bioinformatics methods and publicly available DNA microarray data to predict potential targets of miR395a. GUN5—a multifunctional protein involved in plant metabolic functions such as chlorophyll synthesis and the abscisic acid (ABA) pathway—was identified as a possible target. ABI4 and ABI5, both genes positively regulated by ABA, were down-regulated by EBR treatment. In summary, our results suggest that EBR regulates seedling development and root growth of A. thaliana through miR395a by suppressing GUN5 expression and its downstream signal transduction.     

Visualization of Biosurfactant Film Flow in a Bacillus subtilis Swarm Colony on an Agar Plate

Collective bacterial dynamics plays a crucial role in colony development. Although many research groups have studied the behavior of fluidic swarm colonies, the detailed mechanics of its motion remains elusive. Here, we developed a visualization method using submicron fluorescent beads for investigating the flow field in a thin layer of fluid that covers a Bacillus subtilis swarm colony growing on an agar plate. The beads were initially embedded in the agar plate and subsequently distributed spontaneously at the upper surface of the expanding colony. We conducted long-term live cell imaging of the B. subtilis colony using the fluorescent tracers, and obtained high-resolution velocity maps of microscale vortices in the swarm colony using particle image velocimetry. A distinct periodic fluctuation in the average speed and vorticity of flow in swarm colony was observed at the inner region of the colony, and correlated with the switch between bacterial swarming and growth phases. At the advancing edge of the colony, both the magnitudes of velocity and vorticity of flow in swarm colony were inversely correlated with the spreading speed of the swarm edge. The advanced imaging tool developed in this study would facilitate further understanding of the effect of micro vortices in swarm colony on the collective dynamics of bacteria.     

Exploration of biarsenical chemistry--challenges in protein research

The fluorescent modification of proteins (with genetically encoded low-molecular-mass fluorophores, affinity probes, or other chemically active species) is extraordinarily useful for monitoring and controlling protein functions in vitro, as well as in cell cultures and tissues. The large sizes of some fluorescent tags, such as fluorescent proteins, often perturb normal activity and localization of the protein of interest, as well as other effects. Of the many fluorescent-labeling strategies applied to in vitro and in vivo studies, one is very promising. This requires a very short (6- to 12-residue), appropriately spaced, tetracysteine sequence (-CCXXCC-); this is either placed at a protein terminus, within flexible loops, or incorporated into secondary structure elements. Proteins that contain the tetracysteine motif become highly fluorescent upon labeling with a nonluminescent biarsenical probe, and form very stable covalent complexes. We focus on the development, growth, and multiple applications of this protein research methodology, both in vitro and in vivo. Its application is not limited to intact-cell protein visualization; it has tremendous potential in other protein research disciplines, such as protein purification and activity control, electron microscopy imaging of cells or tissue, protein-protein interaction studies, protein stability, and aggregation studies.     

Photocaged Hoechst Enables Subnuclear Visualization and Cell Selective Staining of DNA in vivo

Selective targeting of DNA by means of fluorescent labeling has become a mainstay in the life sciences. While genetic engineering serves as a powerful technique and allows the visualization of nucleic acid by using DNA-targeting fluorescent fusion proteins in a cell-type- and subcellular-specific manner, it relies on the introduction of foreign genes. On the other hand, DNA-binding small fluorescent molecules can be used without genetic engineering, but they are not spatially restricted. Herein, we report a photocaged version of the DNA dye Hoechst33342 (pcHoechst), which can be uncaged by using UV to blue light for the selective staining of chromosomal DNA in subnuclear regions of live cells. Expanding its application to a vertebrate model organism, we demonstrate uncaging in epithelial cells and short-term cell tracking in vivo in zebrafish. We envision pcHoechst as a valuable tool for targeting and interrogating DNA with precise spatiotemporal resolution in living cells and wild-type organisms.     

On the structure of holographic polymer-dispersed polyethylene glycol

Holographic polymerization (H-P) has been used to fabricate polymer-dispersed liquid crystals and pattern inert nanoparticles. In this article, one-dimensional grating structures of Norland resin and polyethylene glycol (PEG) were achieved using the H-P technique. Both reflection and transmission grating structures were fabricated. The optical properties of the reflection grating structures (also known as Bragg reflectors, BRs) are thermosensitive, which is attributed to the formation and crystallization of PEG crystals. The thermal switching temperature of the BR can be tuned by using different molecular weight PEG samples. The hierarchical structure and morphology of the BR were studied using synchrotron X-ray, polarized light microscopy and transmission electron microscopy. PEG crystals were found to be confined in ∼60 nm thick layers in the BR. Upon crystallization, the PEG lamellae were parallel to the BR surfaces and PEG chains were parallel to the BR normal, resembling the confined crystallization behavior of polyethylene oxide (PEO) in PEO-block-polystyrene (PEO-b-PS) block copolymers. This observation suggests that the tethering effect in the block copolymer systems does not play a major role in PEG chain orientation in the confined nanoenvironment.     

Photoluminescent nanodiamonds: Comparison of the photoluminescence saturation properties of the NV color center and a cyanine dye at the single emitter level,and study of the color center concentration under different preparation conditions

Nitrogen-Vacancy (NV) color centers in diamond nanoparticles (NanoDiamonds, NDs) have a great number of applications, in particular in quantum information processing and as cellular fluorescent labels. In this work we compare the photoluminescence properties of a single NV color center embedded in a 30 nm diameter nanodiamond to that of a single organic fluorescent molecule. We also study the photoluminescence properties of NDs prepared under different conditions in order to find the optimal parameters to achieve a high fluorescence yield, which is still an open question in the case of nanocrystals compared to bulk diamond. The results of this study are of interest for the applications of small and bright diamond nanoparticles in nanophotonics and biology.     

Extracellular Vesicles-Encapsulated Yeast Prions and What They Can Tell Us about the Physical Nature of Propagons

The yeast Saccharomyces cerevisiae hosts an ensemble of protein-based heritable traits, most of which result from the conversion of structurally and functionally diverse cytoplasmic proteins into prion forms. Among these, [PSI⁺], [URE3] and [PIN⁺] are the most well-documented prions and arise from the assembly of Sup35p, Ure2p and Rnq1p, respectively, into insoluble fibrillar assemblies. Yeast prions propagate by molecular chaperone-mediated fragmentation of these aggregates, which generates small self-templating seeds, or propagons. The exact molecular nature of propagons and how they are faithfully transmitted from mother to daughter cells despite spatial protein quality control are not fully understood. In [PSI⁺] cells, Sup35p forms detergent-resistant assemblies detectable on agarose gels under semi-denaturant conditions and cytosolic fluorescent puncta when the protein is fused to green fluorescent protein (GFP); yet, these macroscopic manifestations of [PSI⁺] do not fully correlate with the infectivity measured during growth by the mean of protein infection assays. We also discovered that significant amounts of infectious Sup35p particles are exported via extracellular (EV) and periplasmic (PV) vesicles in a growth phase and glucose-dependent manner. In the present review, I discuss how these vesicles may be a source of actual propagons and a suitable vehicle for their transmission to the bud.     

Accurate Analysis of Tumor Margins Using a Fluorescent pH Low Insertion Peptide (pHLIP)

The recurrence of certain cancers remains quite high due to either incomplete surgical removal of the primary tumor or the presence of small metastases that are invisible to the surgeon. Near infrared (NIR) fluorescence imaging might improve surgical outcomes by providing sensitive, specific, and real-time visualization of normal and diseased tissues if agents can be found that discriminate between normal and diseased tissue and define tumor margins. We have developed a new approach for revealing tumor borders by using NIR fluorescently labeled pH Low Insertion Peptide (pHLIP) and have created a computational program for the quantitative assessment of tumor boundaries. The approach is tested in vivo by co-localization of GFP-tumors and NIR emission from the fluorescently labeled pHLIP, and it is found that boundaries are accurately reported and that sub-millimeter masses can be detected.     

Synthesis and characterization of fluorescent perylene bisimide-containing glycopolymers for Escherichia coli conjugation and cell imaging

Fluorescent glycopolymers were prepared via combined atom transfer radical polymerization (ATRP) and ‘Click Chemistry’ in one-pot synthesis, in the presence of 2-azidoethyl methacrylate (AzEMA), 2-propynyl α-d-mannopyranoside, N,N′-bis{2-[2-[(2-bromo-2-methylpropanoyl)oxy]ethoxy]ethyl}perylene-3,4,9,10-tetracarboxylic acid bisimide (PBI-Br), copper (I) bromide catalyst and pentamethyldiethylenetriamine (PMDETA) ligand. Simultaneous ATRP and ‘Click Chemistry’ is an attractive method for the synthesis of functional glycopolymers as the reaction conditions are compatible with ATRP of an azide monomer, as long as an alkynyl-functionalized carbohydrate is available for click coupling reaction. The fluorescent glycopolymers were characterized by ¹H NMR, FT-IR, UV-visible absorption, fluorescence and X-ray photoelectron spectroscopies, as well as by gel permeation chromatography. Incubation of Escherichia coli (E. coli DH5α) with the fluorescent glycopolymers yielded green fluorescent bacterial clusters. The low cytotoxicity level of the fluorescent glycopolymers was revealed by incubation with 3T3 fibroblasts, macrophages and KB cells in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assays in vitro. Subsequently, the water-soluble, biocompatible and fluorescent glycopolymers were used as effective fluorescent cell labeling agents.     

Preparation of polymer latex particles carrying salt-responsive fluorescent graft chains

We prepared the novel fluorescent polymer latex particles which can change their fluorescence intensity in response to the increasing NaCl concentration in water. Core polymer latex particles were synthesized by emulsifier-free emulsion polymerization of styrene and 2-(2-chloroisobutyroyloxy)ethyl methacrylate. Hydrophilic polymer chains containing epoxy groups were grafted from the core particles by surface-initiated atom transfer radical copolymerization of methoxy polyethyleneglycol methacrylate (MEO_xMA, x = 4 or 9) and glycidyl methacrylate in aqueous media. After azidation of epoxy groups in graft chains, a water-soluble fluorescent dansyl derivative was successfully coupled with the graft chains by copper-catalyzed azide-alkyne cycloaddition in aqueous media. The wavelength of maximum fluorescence intensity of polymer particles carrying graft chains with longer PEG side chains (x = 9) was slightly blue-shifted (7 nm) and the fluorescence intensity increased (1.35 times) with an increase in NaCl concentration as opposed to polymer particles with shorter PEG chains (x = 4).     

Fenarimol,a Pyrimidine-Type Fungicide,Inhibits Brassinosteroid Biosynthesis

The plant steroid hormone brassinosteroids (BRs) are important signal mediators that regulate broad aspects of plant growth and development. With the discovery of brassinoazole (Brz), the first specific inhibitor of BR biosynthesis, several triazole-type BR biosynthesis inhibitors have been developed. In this article, we report that fenarimol (FM), a pyrimidine-type fungicide, exhibits potent inhibitory activity against BR biosynthesis. FM induces dwarfism and the open cotyledon phenotype of Arabidopsis seedlings in the dark. The IC₅₀ value for FM to inhibit stem elongation of Arabidopsis seedlings grown in the dark was approximately 1.8 ± 0.2 μM. FM-induced dwarfism of Arabidopsis seedlings could be restored by brassinolide (BL) but not by gibberellin (GA). Assessment of the target site of FM in BR biosynthesis by feeding BR biosynthesis intermediates indicated that FM interferes with the side chain hydroxylation of BR biosynthesis from campestanol to teasterone. Determination of the binding affinity of FM to purified recombinant CYP90D1 indicated that FM induced a typical type II binding spectrum with a K_d value of approximately 0.79 μM. Quantitative real-time PCR analysis of the expression level of the BR responsive gene in Arabidopsis seedlings indicated that FM induces the BR deficiency in Arabidopsis.     

Labeling the oily core of nanocapsules and lipid-core nanocapsules with a triglyceride conjugated to a fluorescent dye as a strategy to particle tracking in biological studies

The synthesis of novel fluorescent materials represents a very important step to obtain labeled nanoformulations in order to evaluate their biological behavior. The strategy of conjugating a fluorescent dye with triacylglycerol allows that either particles differing regarding supramolecular structure, i.e., nanoemulsions, nanocapsules, lipid-core nanocapsules, or surface charge, i.e., cationic nanocapsules and anionic nanocapsules, can be tracked using the same labeled material. In this way, a rhodamine B-conjugated triglyceride was obtained to prepare fluorescent polymeric nanocapsules. Different formulations were obtained, nanocapsules (NC) or lipid-core nanocapsules (LNC), using the labeled oil and Eudragit RS100, Eudragit S100, or poly(caprolactone) (PCL), respectively. The rhodamine B was coupled with the ricinolein by activating the carboxylic function using a carbodiimide derivative. Thin layer chromatography, proton nuclear magnetic resonance (¹H-NMR), Fourier transform infrared spectroscopy (FTIR), UV-vis, and fluorescence spectroscopy were used to identify the new product. Fluorescent nanocapsule aqueous suspensions were prepared by the solvent displacement method. Their pH values were 4.6 (NC-RS100), 3.5 (NC-S100), and 5.0 (LNC-PCL). The volume-weighted mean diameter (D_4.3) and polydispersity values were 150 nm and 1.05 (NC-RS100), 350 nm and 2.28 (NC-S100), and 270 nm and 1.67 (LNC-PCL). The mean diameters determined by photon correlation spectroscopy (PCS) (z-average) were around 200 nm. The zeta potential values were +5.85 mV (NC-RS100), -21.12 mV (NC-S100), and -19.25 mV (LNC-PCL). The wavelengths of maximum fluorescence emission were 567 nm (NC-RS100 and LNC-PCL) and 574 nm (NC-S100). Fluorescence microscopy was used to evaluate the cell uptake (human macrophage cell line) of the fluorescent nanocapsules in order to show the applicability of the approach. When the cells were treated with the fluorescent nanocapsules, red emission was detected around the cell nucleus. We demonstrated that the rhodamine B-conjugated triglyceride is a promising new material to obtain versatile dye-labeled nanocarriers presenting different chemical nature in their surfaces.     

Application of Fluorescent Proteins for Functional Dissection of the Drosophila Visual System

The Drosophila eye has been used extensively to study numerous aspects of biological systems, for example, spatio-temporal regulation of differentiation, visual signal transduction, protein trafficking and neurodegeneration. Right from the advent of fluorescent proteins (FPs) near the end of the millennium, heterologously expressed fusion proteins comprising FPs have been applied in Drosophila vision research not only for subcellular localization of proteins but also for genetic screens and analysis of photoreceptor function. Here, we summarize applications for FPs used in the Drosophila eye as part of genetic screens, to study rhodopsin expression patterns, subcellular protein localization, membrane protein transport or as genetically encoded biosensors for Ca²⁺ and phospholipids in vivo. We also discuss recently developed FPs that are suitable for super-resolution or correlative light and electron microscopy (CLEM) approaches. Illustrating the possibilities provided by using FPs in Drosophila photoreceptors may aid research in other sensory or neuronal systems that have not yet been studied as well as the Drosophila eye.     

Image-Based In Vitro Screening Reveals the Trypanostatic Activity of Hydroxymethylnitrofurazone against Trypanosoma cruzi

Hydroxymethylnitrofurazone (NFOH) is a therapeutic candidate for Chagas disease (CD). It has negligible hepatotoxicity in a murine model compared to the front-line drug benznidazole (BZN). Here, using Trypanosoma cruzi strains that express bioluminescent and/or fluorescent reporter proteins, we further investigated the in vitro and in vivo activity of NFOH to define whether the compound is trypanocidal or trypanostatic. The in vitro activity was assessed by exploiting the fluorescent reporter strain using wash-out assays and real-time microscopy. For animal experimentation, BALB/c mice were inoculated with the bioluminescent reporter strain and assessed by highly sensitive in vivo and ex vivo imaging. Cyclophosphamide treatment was used to promote parasite relapse in the chronic stage of infection. Our data show that NFOH acts by a trypanostatic mechanism, and that it is more active than BZN in vitro against the infectious trypomastigote form of Trypanosoma cruzi. We also found that it is more effective at curing experimental infections in the chronic stage, compared with the acute stage, a feature that it shares with BZN. Therefore, given its reduced toxicity, enhanced anti-trypomastigote activity, and curative properties, NFOH can be considered as a potential therapeutic option for Chagas disease, perhaps in combination with other trypanocidal agents.     

Performance evaluation of high‐cis 1,4‐polybutadienes

This article reports the results of a study comparing commercially available high‐cis polybutadiene rubbers (BRs) proceeding from different production technologies and bearing distinct structural characteristics. The microstructure of these polymers was characterized by Fourier transform infrared spectroscopy; molecular weight and polydispersity values were characterized by size exclusion chromatography (SEC). The degree of branching was characterized by SEC and dynamic mechanical rheological testing (RPA 2000). Glass‐transition temperature was characterized by differential scanning calorimetry, and rheological properties were characterized with an oscillating rheometer rubber process analyzer (RPA 2000). Tire tread formulations were prepared with carbon black HAF N‐339 as a reinforcement filler, and we compared the mechanical properties and performance of the different elastomer compositions. The compositions were characterized by their rheological properties, tensile resistance, resistance to abrasion, resistance to tearing, permanent deformation, resilience, and fatigue properties. The tested compositions obtained from BRs with distinct structural characteristics showed different performances. Neodymium‐salt‐based catalysts produced BRs with higher cis‐1,4 levels and higher linearities. These polymer compositions also showed higher performances in abrasion resistance, fatigue resistance, and resilience tests. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 88–99, 2006     

Chemoenzymatic Preparation of Functional Click-Labeled Messenger RNA

Synthetic mRNAs are promising candidates for a new class of transformative drugs that provide genetic information for patients’ cells to develop their own cure. One key advancement to develop so-called druggable mRNAs was the preparation of chemically modified mRNAs, by replacing standard bases with modified bases, such as uridine with pseudouridine, which can ameliorate the immunogenic profile and translation efficiency of the mRNA. Thus the introduction of modified nucleobases was the foundation for the clinical use of such mRNAs. Herein we describe modular and simple methods to chemoenzymatically modify mRNA. Alkyne- and/or azide-modified nucleotides are enzymatically incorporated into mRNA and subsequently conjugated to fluorescent dyes using click chemistry. This allows visualization of the labeled mRNA inside cells. mRNA coding for the enhanced green fluorescent protein (eGFP) was chosen as a model system and the successful expression of eGFP demonstrated that our modified mRNA is accepted by the translation machinery.