Controlling Surface Segregation of a Polymer To Display Carboxy Groups on an Outermost Surface Using Perfluoroacyl Groups

Controlling the surface properties of solid polymers is important for practical applications. We here succeeded in controlling the surface segregation of polymers to display carboxy groups on an outermost surface, which allowed the covalent immobilization of functional molecules via the carboxy groups on a substrate surface. Random methacrylate-based copolymers containing carboxy groups, which were protected with perfluoroacyl (R_f) groups, were dip-coated on acrylic substrate surfaces. X-ray photoelectron spectroscopy and contact-angle measurements revealed that the R_f groups were segregated to the outermost surface of the dip-coated substrates. The R_f groups were removed by hydrolysis of the R_f esters in the copolymers, resulting in the display of carboxy groups on the surface. The quantification of carboxy groups on a surface revealed that the carboxy groups were reactive to a water-soluble solute in an aqueous solution. The surface segregation was affected by the molecular structure of the copolymer used for dip-coating

Surfactant-Induced Polymer Segregation To Produce Antifouling Surfaces via Dip-Coating with an Amphiphilic Polymer

We propose a rational strategy to control the surface segregation of an amphiphilic copolymer in its dip-coating with a low-molecular-weight surfactant. We synthesized a water-insoluble methacrylate-based copolymer containing oligo­(ethylene glycol) (OEG) (copolymer <b>1</b>) and a perfluoroalkylated surfactant (surfactant <b>1</b>) containing OEG. The dip-coating of copolymer <b>1</b> with surfactant <b>1</b> resulted in the segregation of surfactant <b>1</b> on the top surface of the dip-coated layer due to the high hydrophobicity of its perfluoroalkyl group. OEG moieties of surfactant <b>1</b> were accompanied by those of copolymer <b>1</b> in its segregation, allowing the OEG moieties of copolymer <b>1</b> to be located just below the top surface of the dip-coated layer. The removal of surfactant <b>1</b> produced the surface covered by the OEG moieties of the copolymer that exhibited antifouling properties. Using this strategy, we also succeeded in the introduction of carboxy groups on the dip-coated surface and demonstrated that the carboxy groups were available for the immobilization of functional molecules on the surface

Autophagy-mediated regulation of phytohormone metabolism during rice anther development

<p>Autophagy has recently been shown to be required for postmeiotic anther development including anther dehiscence, programmed cell death-mediated degradation of the tapetum and pollen maturation in rice. Several phytohormones are known to play essential roles during male reproductive development including pollen maturation. However, the relationship between phytohormone metabolism and autophagy in plant reproductive development is unknown. We here comprehensively analyzed the effect of autophagy disruption on phytohormone contents in rice anthers at the flowering stage, and found that endogenous levels of active-forms of gibberellins (GAs) and cytokinin, trans-zeatin, were significantly lower in the autophagy-defective mutant, Os<i>atg7–1</i>, than in the wild type. Treatment with GA₄ partially recovered maturation of the mutant pollens, but did not recover the limited anther dehiscence as well as sterility phenotype. These results suggest that autophagy affects metabolism and endogenous levels of GAs and cytokinin in rice anthers. Reduction in bioactive GAs in the autophagy-deficient mutant may partially explain the defects in pollen maturation of the autophagy-deficient mutant, but tapetal autophagy also plays other specific roles in fertilization.</p

An S-Type Anion Channel SLAC1 Is Involved in Cryptogein-Induced Ion Fluxes and Modulates Hypersensitive Responses in Tobacco BY-2 Cells

<div><p>Pharmacological evidence suggests that anion channel-mediated plasma membrane anion effluxes are crucial in early defense signaling to induce immune responses and hypersensitive cell death in plants. However, their molecular bases and regulation remain largely unknown. We overexpressed Arabidopsis <i>SLAC1</i>, an S-type anion channel involved in stomatal closure, in cultured tobacco BY-2 cells and analyzed the effect on cryptogein-induced defense responses including fluxes of Cl⁻ and other ions, production of reactive oxygen species (ROS), gene expression and hypersensitive responses. The SLAC1-GFP fusion protein was localized at the plasma membrane in BY-2 cells. Overexpression of <i>SLAC1</i> enhanced cryptogein-induced Cl⁻ efflux and extracellular alkalinization as well as rapid/transient and slow/prolonged phases of NADPH oxidase-mediated ROS production, which was suppressed by an anion channel inhibitor, DIDS. The overexpressor also showed enhanced sensitivity to cryptogein to induce downstream immune responses, including the induction of defense marker genes and the hypersensitive cell death. These results suggest that SLAC1 expressed in BY-2 cells mediates cryptogein-induced plasma membrane Cl⁻ efflux to positively modulate the elicitor-triggered activation of other ion fluxes, ROS as well as a wide range of defense signaling pathways. These findings shed light on the possible involvement of the SLAC/SLAH family anion channels in cryptogein signaling to trigger the plasma membrane ion channel cascade in the plant defense signal transduction network.</p></div

Effect of <i>SLAC1</i>-overexpression on cryptogein-induced defense gene expressions.

<p>(A and B) Cryptogein-induced the expression of <i>HIN1</i> in a dose-dependent manner (A) and <i>Hsr203j</i> (B) in <i>SLAC1</i>-overexpressing cells. The amount of each mRNA was calculated from the threshold point located in the log-linear range of the RT-PCR. The relative level of each gene in the control cells at time 0. Total RNA was isolated from BY-2 cells harvested 5 h after the addition of cryptogein at various concentrations. Data are the mean ± SE of three independent experiments. * <i>p</i><0.05, ** <i>p</i><0.005, significantly different from the control line.</p