In-Kyu Kang

Cell behaviour on polymer surfaces with different functional groups.

Surfaces with differently chargeable functional groups were prepared on low density polyethylene sheets by corona discharge treatment, followed by graft copolymerization of acrylic acid (-COOH, negatively chargeable) and a subsequent substitution reaction of carboxylic acid groups to hydroxyl (-CH2OH, neutral) or amide (-CONH2, neutral) groups. The amide groups grafted on the surface were further converted to amine groups (-CH2NH2, positively chargeable). The prepared surfaces were characterized by measuring the water contact angle, electron spectroscopy for chemical analysis and Fourier-transform infrared spectroscopy in the attenuated total reflectance mode. It was observed that the wettability of the different functional group-grafted surfaces largely increases compared with the control surface but is not much affected by the kind of functional groups grafted. The interaction of Chinese hamster ovary cells with the functional group-grafted surfaces was investigated. The cells adhered and grown on the surfaces were counted using an electronic cell counter and observed by a scanning electron microscope. The surface grafted with amine groups was best for cell adhesion, spreading and growth probably owing to the positively chargeable character in aqueous cell culture medium. For surfaces grafted with neutral functional groups, the surface grafted with hydroxyl groups showed better cell spreading than that grafted with amide groups.

Albumin release from bioerodible hydrogels based on semi-interpenetrating polymer networks composed of poly(ϵ-caprolactone) and poly(ethylene glycol) macromer

Poly(ethylene glycol) (PEG) macromers terminated with acrylate groups and semi-interpenetrating polymer networks (SIPNs) composed of poly(ϵ-caprolactone)(PCL) and PEG macromer were synthesized and characterized to obtain a bioerodible hydrogel that can be used for albumin delivery. Polymerization of PEG macromer resulted in the formation of cross-linked gels due to the multifunctionality of macromer. Glass transition temperature (Tg) and melting temperature (Tm) of PEG network and PCL in the SIPNs were inner-shifted, indicating an interpenetration of PCL and PEG chains. Water content in the SIPNs increased with increasing PEG weight fraction due to the hydrophilicity of PEG. The amount of albumin released from the SIPNs increased with higher PEG content in the SIPNs, higher drug loading, lower concentration of PEG macromer during the SIPNs preparation, and the higher molecular weight of PEG. The degradation rate of the SIPNs gels in vitro increased with increasing of PEG weight fraction.

Biological Characterization of Marssonina coronaria Associated with Apple Blotch Disease

Abstract Marssonina coronaria associated with apple blotch disease causes severe premature defoliation, and is widely distributed in Korea. Thirteen isolates were collected from orchards located in Gyeongbuk Province from 2005~2007. All isolates displayed over 99.6% and 99.2% sequence similarity to each other in internal transcribed spacer regions and partial sequences of 28S rDNA, respectively. The isolates were phylogenetically closely related to Chinese isolates. Selected isolates did not differ in their pathogenicity. The optimum conditions for fungal growth were 20°C and pH 6 on peptone potato dextrose agar (PPDA). Peptone and mannose were the best nitrogen and carbon source, respectively. Fungal growth was better on PPDA than on common potato dextrose agar. This study provides valuable information for integrated disease management program and facilitates the routine culturing of M. coronaria.

Release of 8-hydroxyquinoline from copolymers of 8-quinolinyl acrylate and acrylamide

Abstract Radical copolymerization of 8-quinolinyl acrylate (QA) with acrylamide (AM) was carried out in dimethyl sulfoxide at 70°C in order to synthesize hydrophilic polymers which are able to release 8-hydroxyquinoline (HQ). From the composition of poly(QA-co-AM) prepared, the monomer reactivity ratios were determined to be 1.97 for QA and 0.34 for AM. From the hydrolysis of the polymers, it was shown that the release of HQ increased with increasing contents of the hydrophilic AM in the copolymer and with increasing pH of the release medium.

Hymenobacter daeguensis sp. nov. isolated from river water

A Gram-stain-negative, non-motile, non-spore-forming, rod-shaped, aerobic bacterial strain, designated 16F3Y-2T, was isolated from the Han River, South Korea, and was characterized taxonomically using a polyphasic approach. Comparative 16S rRNA gene sequence analysis showed that strain 16F3Y-2T belonged to the family Cytophagaceae in the phylum Bacteroidetes and was most closely related to ‘Hymenobacter terrae’ DG7A (98.01%), H. soli PB17T (97.26%), H. glaciei VUG-A130T (96.78%), H. antarcticus VUG-A42aaT (96.72%), H. ruber PB156T (96.61%), and H. saemangeumensis GSR0100T (95.77%). The G+C content of the genomic DNA of strain 16F3Y-2T was 62.9 mol%. The isolate contained MK-7 as the predominant respiratory quinone, and summed feature 3 (C16:1ω7c/C16:1ω6c; 35.5%), C15:0 iso (16.9%), C16:1ω5c (10.9%), and C15:0 anteiso (9.9%) as major fatty acids. The major polar lipid was phosphatidylethanolamine. Phenotypic and chemotaxonomic data supported the affiliation of strain 16F3Y-2T with the genus Hymenobacter. However, strain 16F3Y-2T exhibited relatively low levels of DNA-DNA relatedness with ‘H. terrae’ KCTC 32554 (44.1%) and H. soli KCTC 12607T (24.3%), clearly indicating that the isolate constitutes a new genospecies. Strain 16F3Y-2T could be differentiated from its phylogenetic neighbors on the basis of several phenotypic, genotypic, and chemotaxonomic features. Therefore, strain 16F3Y-2T represents a novel species in the genus Hymenobacter, for which the name Hymenobacter daeguensis sp. nov. is proposed. The type strain is 16F3Y-2T (=KCTC 52537T =JCM 31654T).

Mapping of Novel QTL Regulating Grain Shattering Using Doubled Haploid Population in Rice (Oryza sativa L.)

The critical evolutionary step during domestication of major cereals was elimination of seed shattering because the easy-to-shatter trait in wild relatives results in a severe reduction in yield. In this study, we analyzed the QTLs associated with shattering employing a high-density genetic map in doubled haploid (DH) population of rice (Oryza sativa L.). A genetic linkage map was generated with 217 microsatellite markers spanning 2082.4 cM and covering 12 rice chromosomes with an average interval of 9.6 cM between markers based on 120 DHLs derived from a cross between Cheongcheong indica type cultivar and Nagdong japonica type cultivar. In the QTL analysis, five QTLs pertaining to the breaking tensile strength (BTS) were detected in 2013 and 2015. Two regions of the QTLs related to BTS on chromosome 1 and chromosome 6 were detected. Several important genes are distributed in 1 Mbp region of the QTL on chromosome 6 and they are related to the formation of abscission layer. We decide to name this QTL qSh6 and the candidate genes in the qSh6 region can be employed usefully in further research for cloning.

Simultaneous identification of Grapholita molesta Busck and Grapholita dimorpha Komai by PCR-RFLP

Although several molecular diagnostic techniques are available for the identification of the apple‐feeding pests Grapholita molesta Busck and Grapholita dimorpha Komai, these pests are severely affecting apple orchards in Korea. These two pests may be misidentified or the available molecular diagnostic techniques may not facilitate the simultaneous identification of the morphological features of both species. In this study, we developed a multiplex assay for these two species using the polymerase chain reaction – restriction fragment length polymorphism (PCR‐RFLP) method. Sixty‐two specimens were collected from apples presumed infested with moth larvae and from pheromone traps from 2013 to 2014. Both species were identified morphologically, and a partial region of the cytochrome b gene was sequenced to design primers for PCR‐RFLP. Digestion profiles of G. molesta and G. dimorpha, using the Sau3A1 restriction enzyme, were characterized using three DNA fragments each for G. molesta (363 bp, 91 bp and 31 bp) and G. dimorpha (220 bp, 234 bp and 31 bp). The RFLP assay developed for both species in this study was more efficient and accurate than other currently used diagnostic assays and would be helpful to identify field‐collected specimens for pest control research.

Physiological responses to drought stress of transgenic Chinese cabbage expressing Arabidopsis H+-pyrophosphatase

Plant tolerance to drought is a beneficial trait for stabilizing crop productivity under water deficits. Here we report that genetically engineered Chinese cabbage expressing Arabidopsis H-pyrophosphatase (AVP1) shows enhanced physiological parameters related to drought tolerance. In comparison with wild type plants under soil water deficit stress created by cessation of irrigation, soil water potential in pot with AVP1-expressing plants was more rapidly decreased that might lead to increased relative water content in leaves, while both genotypes had indistinguishable wilting phenotypes. Transgenic plants subjected to drought treatment also exhibited higher photosystem II quantum yield in addition to lower electrolyte leakage and H2O2-3,3’-diaminobenzidine content when compared to wild type plants.

Occurrence of bacterial rot of onion caused by Bacillus amyloliquefaciens in Korea

In 2008, bacterial rot on onion bulbs (Allium cepa L.) was observed in several low-temperature warehouses in Changnyeong-gun, Korea. The causal pathogen was isolated and identified as Bacillus amyloliquefaciens based on morphological and biochemical characterization and sequence analysis of its genome. The isolated bacteria caused the same rot symptom on inoculated onion bulbs as found in naturally infected onions during storage and was reisolated from these bulbs. This is the first report of bacterial rot of onion caused by B. amyloliquefaciens in Korea.

Effects of Growth Regulators and Culture Environment on ex vitro Rooting and Acclimatization of Apple Rootstock in vitro Propagated

Growth of M.9 (Malus domestica Bark. cv) and M.26 (Malus domestica Bark. cv) of dwarf apple rootstock, cultured on MS agar medium in a vessel with ventilating stopper (VS) and then in vivo rooting and acclimatization under combined-treatment by some materials with IBA, were investigated. Concentration of and ethylene in the vessel with VS was lower then in the vessel with non-VS. Change of temperature and humidity in the vessel with VS was repeated by light condition. Stomatal pares of tissue in the vessel with VS were immediately closed after plantlets were exposed to room humidity but those in the vessel with non-VS were opened after 20 minutes exposure to room humidity. Leaf area and chloroplast index of tissue in the vessel with VS was higher then in the vessel with non-VS. In vivo rooting ratio and acclimatization ratio of M.9 and M.26 was highest in 300mg/L IBA＋3％ sucrose dip-treatment among other combined- treatments.