Hyun Suk Cho

Variation and correlation analysis of flavonoids and carotenoids in Korean pigmented rice (Oryza sativa L.) cultivars.

Flavonoids and carotenoids of pigmented rice ( Oryza sativa L.), including five black cultivars and two red cultivars, from Korea were characterized to determine the diversity among the phytochemicals and to analyze the relationships among their contents. Black cultivars were higher in flavonoids and carotenoids than the red and white cultivars. The profiles of eight phytochemicals identified from the rice grains were subjected to principal component analysis (PCA) to evaluate the differences among cultivars. PCA could fully distinguish between these cultivars. The Heugjinjubyeo (BR-1) and Heugseolbyeo (BR-2) cultivars were separated from the others based on flavonoid and carotenoid concentrations. Flavonoid contents had a positive correlation with carotenoid contents among all rice grains. The BR-1 and BR-2 cultivars appear to be good candidates for future breeding programs because they have simultaneously high flavonoid and carotenoid contents.

Unintended polar metabolite profiling of carotenoid-biofortified transgenic rice reveals substantial equivalence to its non-transgenic counterpart

Substantial equivalence is a critical concept for biosafety assessment of genetically modified (GM) crops. To investigate substantial equivalence among carotenoid-biofortified GM rice and five conventional rice cultivars having common white (three) and red (two) grain colors, profiles of 52 polar metabolites were analyzed using gas chromatography time-of-flight mass spectrometry. The results were compared to evaluate the differences among GM and non-GM rice cultivars using principal components analysis. The GM rice is more comparable to its non-transgenic counterpart rice variety according to the closer co-separation than for other cultivars tested. This suggests that profiling of unintended polar metabolites could be a useful tool to reveal substantial equivalence of GM rice.

Expression of PAT and NPT II proteins during the developmental stages of a genetically modified pepper developed in Korea.

Estimation of the protein levels introduced in a biotechnology-derived product is conducted as part of an overall safety assessment. An enzyme-linked immunosorbent assay (ELISA) was used to analyze phosphinothricin acetyltransferase (PAT) and neomycin phosphotransferase II (NPT II) protein expression in a genetically modified (GM) pepper plant developed in Korea. PAT and NPT II expression levels, based on both dry weight and fresh weight, were variable among different plant generations and plant sections from isolated genetically modified organism (GMO) fields at four developmental stages. PAT expression was highest in leaves at anthesis (11.44 μg/gdw and 2.17 μg/gfw) and lowest in roots (0.12 μg/gdw and 0.01 μg/gfw). NPT II expression was also highest in leaves at anthesis (17.31 μg/gdw and 3.41 μg/gfw) and lowest in red pepper (0.65 μg/gdw and 0.12 μg/gfw). In pollen, PAT expression was 0.59-0.62 μg/gdw, while NPT II was not detected. Both PAT and NPT II showed a general pattern of decreased expression with progression of the growing season. As expected, PAT and NPT II protein expression was not detectable in control pepper plants.

Comparative Analysis of Phytochemicals and Polar Metabolites from Colored Sweet Potato (Ipomoea batatas L.) Tubers

We determined the phytochemical diversity, including carotenoids, flavonoids, anthocyanins, and phenolic acids, in sweet potatoes (Ipomoea batatas L.) with distinctive flesh colors (white, orange, and purple) and identified hydrophilic primary metabolites. Carotenoid content was considerably higher in orange-fleshed sweet potatoes, wherein β-carotene was the most plentiful, and anthocyanins were detected only in purple-fleshed sweet potatoes. The levels of phenolic acids and flavonoids were relatively higher in purple-fleshed sweet potatoes than those in the other two varieties. Forty-one primary and 18 secondary metabolite profiles were subjected to multivariate statistical analyses, which fully distinguished among the varieties and separated orange- and purple-fleshed sweet potatoes from white-fleshed sweet potatoes based on the high levels of sugars, sugar alcohols, and secondary metabolites. This is the first study to determine comprehensive metabolic differences among different color-fleshed sweet potatoes and provides useful information for genetic manipulation of sweet potatoes to influence primary and secondary metabolism.

Quantification of mCry1Ac1 and PAT proteins during growth of genetically modified rice developed in Korea

The genetically modified (GM) rice, which expresses the insecticidal toxin modified Cry1Ac1 (mCry1Ac1) and the selectable marker phosphinothricin acetyltransferase (PAT), was developed by the Rural Development Administration in Korea. In this study, we used enzyme-linked immunosorbent assay to analyze mCry1Ac1 and PAT protein levels in GM rice. The levels of expression of both transgenes in ‘Agb0101’ (Oryza sativa L. cv. Nakdongbyeo) changed significantly over time, with the plant part, and growth stage. In leaves, mCry1Ac1 expression was the highest at the tillering stage (831 μg/gdw and 301 μg/gfw) and lowest in brown rice seeds (0.25 μg/gdw and 0.19 μg/gfw). Expression of PAT was also highest in leaves at the booting stage (97.49 μg/ gdw and 32.17 μg/gfw) and lowest in polished rice (1.02 μg/gdw and 0.78 μg/gfw). Unlike PAT protein, mCry1Ac1 was not detected in polished rice seeds. As expected, expression of mCry1Ac1 and PAT proteins was not detectable in control rice plants. In general, mCry1Ac1 and PAT levels declined steadily over the course of the plant life cycle.

Soil Microbial Community Assessment for the Rhizosphere Soil of Herbicide Resistant Genetically Modified Chinese Cabbage

BACKGROUND: Cultivation of genetically modified(GM) crops rapidly has increased in the global agricultural area. Among those, herbicide resistant GM crops are reported to have occupied 89.3 million hectares in 2010. However, cultivation of GM crops in the field evoked the concern of the possibility of gene transfer from transgenic plant into soil microorganisms. In our present study, we have assessed the effects of herbicide-resistant GM Chinese cabbage on the surrounding soil microbial community. METHODS AND RESULTS: The effects of a herbicideresistant genetically modified (GM) Chinese cabbage on the soil microbial community in its field of growth were assessed using a conventional culture technique and also culture-independent molecular methods. Three replicate field plots were planted with a single GM and four non-GM Chinese cabbages (these included a non-GM counterpart). The soils around these plants were compared using colony counting, denaturing gradient gel electrophoresis and a species diversity index assessment during the growing periods. The bacterial, fungal and actinomycetes population densities of the GM Chinese cabbage soils were found to be within the range of those of the non-GM Chinese cabbage soils. The DGGE banding patterns of the GM and non-GM soils were also similar, suggesting that the bacterial community structures were stable within a given month and were unaffected by the presence of a GM plant. The similarities of the bacterial species diversity indices were consistent with this finding. CONCLUSION: These results indicate that soil microbial communities are unaffected by the cultivation of herbicide-resistant GM Chinese cabbage within the experimental time frame.

Compositional analyses of diverse phytochemicals and polar metabolites from different-colored potato (Solanum tubersum L.) tubers

Lipophilic bioactive compounds and hydrophilic primary metabolites from potato (solanum tubersum L.) tubers with different-colored flesh (white-, yellow-, red-, and purple) were characterized. The carotenoid content was relatively higher in red-colored potatoes, in which lutein was most plentiful. Among the other lipophilic compounds analyzed, including policosanols, tocopherols, and phytosterols, octacosanol was measured in the largest amount, followed by β-sitosterol, irrespective of color variations. Forty-three hydrophilics consisting of amino acids, organic acids, sugars, and sugar alcohols and 18 lipophilics were subjected to data-mining processes. The results of multivariate statistical analyses clearly distincted the different varieties and separated red-fleshed potatoes from other color-fleshed potatoes according to abundance of amino acids, sugars, and carotenoids. This study confirmed the metabolic association-related biochemical pathway between metabolite characteristic and color differences in potato tubers. These results can facilitate understanding the metabolic differences among diverse colored potatoes and provide fruitful information for genetic engineering of potato cultivars.