Background : Methicillin-Resistant Staphylococcus aureus (MRSA) is a multidrug-resistant (MDR) strain. Especially, MRSA is developing resistance to available antibacterial agents and causing complications in the treatment of infections related to skin, soft tissue, respiratory, bone, joint, and endovascular disorders. Therefore, antibacterial agent combination therapy appears to be a useful option, particularly in developing countries where antibiotic availability is limited. (+)-Usnic acid (UA) is uniquely found in lichens, and is especially abundant in genera such as Usnea and Cladonia. UA has antimicrobial activity against human and plant pathogens. Therefore, UA may be a good antibacterial drug candidate for clinical development. Methods and Results : In search of a natural products capable of inhibiting this multidrug-resistant bacteria, we have investigated the antimicrobial activity of UA against MRSA. In this study, the effects of a combination of UA and permeable agents against MRSA were investigated. For the measurement of cell wall permeability, UA with concentration of Ethylenediaminetetraacetic acid (EDTA) was used. In the other hand, Sodium azide (NaN3) was used as inhibitors of ATPase. These results suggest that the antibacterial effect of UA was potentiated by membrane-binding agents and ABC transporter-inhibiting agents, implying that antibacterial activity is associated with damage of the cell wall and inhibition of ATPase function by UA. Conclusion : UA and in combination with EDTA and NaN3 could lead to the development of new combination antibiotics against MRSA infection. The results of this study appear to be promising, and they are expected to enhance the use of natural products as drugs.

Developing rice lines with various amylose contents is necessary to diverse usages of rice in terms of raw materials for processed food production, and thereby to promote rice consumption in Korea. A rice mutant line, ‘Namil(SA)-dull1’ was established through sodium azide mutagenesis on ‘Namil’, a non-glutinous Korean Japonica rice cultivar. Namil(SA)-dull1’ had dull endosperm characteristics and the evaluated amylose content was 12.2%. A total of 94 F2 progenies from a cross between ‘Namil(SA)-dull1’ and ‘Milyang23’, a non-glutinous Tongil-type rice cultivar, was used for genetic studies on the endosperm amylose content. Association analyses, between marker genotypes of 53 SSR anchor markers and evaluated amylose contents of each 94 F2:3 seeds, initially localized rice chromosome 6 as the harboring place for the modified allele(s) directing low amylose content of ‘Namil(SA)-dull1’. By increasing SSR marker density on the putative chromosomal region followed by association analyses, the target region was narrowed down 0.94 Mbp segment, expanding from 28.95 Mbp to 29.89 Mbp, on rice chromosome 6 pseudomolecule. Among the SSR loci, RM7555 explained 84.2% of total variation of amylose contents in the F2 population. Further physical mapping on the target region directing low amylose content of ‘Namil(SA)-dull1’ would increase the breeding efficiency in developing promising rice cultivars with various endosperm characteristics.

To investigate dose-effect of a chemical mutagen, sodium azide on a rice elite line, Suweon472, seed aliquots were treated with five different concentrations of sodium azide. The degree of mutation levels of each aizde concentration were estimated by using DNA fingerprinting techniques such as RAPD and AFLP. Some selected mutant lines (M4) were also subjected for DNA fingerprinting to estimate their mutation levels by comparing the banding patterns of the wild type, Suweon 472. RAPD and AFLP fingerprinting patterns indicated that dose-effect of different azide concentrations was not clear. With allele description of detected AFLPs among favorable mutant lines, it was possible to discriminate each mutant line from others which have similar phenotypes and reactions against pathogens. AFLP fingerprinting patterns of waxy mutant lines, otherwise, were highly homogeneous as well as their phenotypic and agronomic characters.

To investigate the mutagenecity of sodium azide (SA) and to select mutants having various agronomic characteristics in rice (Oryza sativa L. ssp. japonica), dry seeds of rice variety 'Suweon 472' were treated with 0, 0.5, 1.0, 2.0, and 4.0 mM SA solutions prepared in 0.1 M phosphate buffer (pH 3.0). Germination rate, seedling height and sterility were investigated in M1 generation and chlorophyll mutations were observed in M3 generation. Germination rate and seedling height decreased as the increase of SA concentration in M1 generation, the maximum seed sterility (40.8%) was found at 4.0 mM SA concentration. Chlorophyll mutants were occurred in M3 generation and the frequency calculated on a line basis was 13.5% at the same treatment. Many kinds of mutations for morphological and agronomic characters were observed and mutations with short culm and glabrous leaf were frequently found in M3 generation. Interestingly, five mutant lines resistant to blast or bacterial blight (BB) were selected and evaluated with several isolates in M3 generation although Suweon 472 has been known to be susceptible to blast and BB. These mutants showed all resistance to seven isolates of blast and a total of 76 lines among 2,567 lines evaluated showed resistant to race K1 of bacterial blight. Two mutant lines (440172 and 41272) showed different reaction to BB isolates from the other resistant mutants. A few kinds of endosperm mutants were also identified and most of them were waxy mutants.

Rice consumption per capta, in South Korea, has been decreased dramatically, owing to the changes of living patterns. Because of not only the major energy source of Korean people but also major income source of Korean farmers, diversifying end-use-quality of rice has been demanded. To the context, 'Suweon 472', a high yielding and early mature japonica line and released as 'Namilbyeo' to framers in 2002, was treated with a chemical mutagen, Sodium Azide to find endosperm mutant types. A total of nine endosperm mutat lines, including five waxy, one dull, two floury, and one white core type, were identified from the 3,542 mutatagen treated lines. Amylose contents, iodine reaction, disintegration in alkali solution, gelatinization in urea solution and amylogram properties of those nine endosperm mutant lines were evaluated to address the possibility as new genetic materials for diversifying rice quality of Korean japonica cultivars. All embryo mutants were clearly differentiated from their wild type, 'Suweon 472', in terms of physic-chemical properties evaluated. The endosperm mutant lines would be very useful in expanding untiliztation of rice through opening new rice markets of processed foods from Korean japonica rice.