Synthesis of Photodegradable Polystyrene with Trithiocarbonate as Linkages.

Multiblock polystyrenes (PS) with trithiocarbonate groups as linkages are prepared via reversible addition-fragmentation chain-transfer polymerization using polytrithiocarbonate as a chain transfer agent. The photodegradability of the multiblock PS in the solid state is investigated under UV irradiation at room temperature in an air atmosphere. The experimental results demonstrate that the trithiocarbonate linkages in the multiblock PS can be broken under UV light irradiation at room temperature and the multiblock PS is degraded into separate PS blocks. Gel permeation chromatography measurement reveals that the molecular weight of multiblock PS is reduced from 27 900 to 7900 g mol(-1) after UV light irradiation for 745 h. Moreover, the thermal stability of the multiblock PS is examined and the results indicate that the incorporation of trithiocarbonate shows little influence on the thermal stability of multiblock PS.

[Revealing the chemical changes of tea cell wall induced by anthracnose with confocal Raman microscopy].

Healthy tea and tea infected by anthracnose were first studied by confocal Raman microscopy to illustrate chemical changes of cell wall in the present paper. Firstly, Raman spectra of both healthy and infected sample tissues were collected with spatial resolution at micron-level, and ultrastructure of healthy and infected tea cells was got from scanning electron microscope. These results showed that there were significant changes in Raman shift and Raman intensity between healthy and infected cell walls, indicating that great differences occurred in chemical compositions of cell walls between healthy and infected samples. In details, intensities at many Raman bands which were closely associated with cellulose, pectin, esters were reduced after infection, revealing that the content of chemical compounds such as cellulose, pectin, esters was decreased after infection. Subsequently, chemical imaging of both healthy and infected tea cell walls were realized based on Raman fingerprint spectra of cellulose and microscopic spatial structure. It was found that not only the content of cellulose was reduced greatly after infection, but also the ordered structure of cellulose was destroyed by anthracnose infection. Thus, confocal Raman microscopy was shown to be a powerful tool to detect the chemical changes in cell wall of tea caused by anthracnose without any chemical treatment or staining. This research firstly applied confocal Raman microscopy in phytopathology for the study of interactive relationship between host and pathogen, and it will also open a new way for intensive study of host-pathogen at cellular level.

GhODO1, an R2R3-type MYB transcription factor, positively regulates cotton resistance to Verticillium dahliae via the lignin biosynthesis and jasmonic acid signaling pathway.

In plants, MYB transcription factors play diverse roles in growth, development, and response to abiotic and biotic stresses. However, the signaling processes of these transcription factors in defense against pathogen attacks remain largely unknown. This study isolated a novel R2R3-type MYB transcription factor GhODO1 from cotton (Gossypium hirsutum) and functionally characterized its positive role in tolerance to Verticillium dahliae. GhODO1 was induced by V. dahliae and jasmonic acid (JA) and transient expression of fused GhODO1-GFP in onion epidermal cells showed that GhODO1 protein was localized in the cell nucleus. Knockdown of GhODO1 significantly reduced the resistance of cotton to V. dahliae, whereas GhODO1 ectopic overexpression in Arabidopsis conferred enhanced resistance to V. dahliae. Lignin deposition was significantly decreased in GhODO1-silenced cotton plants after V. dahliae inoculation and mock treatment. The expression levels of genes and activities of enzymes involved in lignin biosynthesis were reduced in GhODO1-silenced cotton plants compared to the TRV:00. Yeast one-hybrid assays revealed that GhODO1 protein interacts with the promoters of lignin biosynthesis-related genes Gh4CL1 and GhCAD3, directly activates their expression, and enhances total lignin accumulation. Moreover, GhODO1 silencing compromised JA-mediated defense signaling and JA accumulation. These results show that GhODO1 is involved in cotton resistance to V. dahliae by involving the lignin biosynthesis and the JA signaling pathway.

Release properties of tannic acid from hydrogen bond driven antioxidative cellulose nanofibrous films.

Layer-by-layer (LBL) assembled films have been exploited for surface-mediated bioactive compound delivery. Here, an antioxidative hydrogen-bonded multilayer electrospun nanofibrous film was fabricated from tannic acid (TA), acting as a polyphenolic antioxidant, and poly(ethylene glycol) (PEG) via layer-by-layer assembly. It overcame the burst release behavior of nanofibrous carrier, due to the reversible/dynamic nature of hydrogen bond, which was responded to external stimuli. The PEG/TA nanofibrous films disassembled gradually and released TA to the media, when soaked in aqueous solutions. The release rate of TA increased with increasing bilayer number, pH and temperature, but decreased with enhancing ionic strength. The surface morphology of the nanofibrous mats was observed by scanning electron microscopy (SEM). The following antioxidant activity assay revealed that it could scavenge DPPH free radicals and ABTS(+) cation radicals, a major biological activity of polyphenols. This technology can be used to fabricate other phenolic-containing slowly releasing antioxidative nanofibrous films.