Soo-Kwon Park

The identification of candidate rice genes that confer resistance to the brown planthopper (Nilaparvata lugens) through representational difference analysis

The development of rice varieties (Oryza sativa L.) that are resistant to the brown planthopper (BPH; Nilaparvata lugens Stål) is an important objective in current breeding programs. In this study, we generated 132 BC5F5 near-isogenic rice lines (NILs) by five backcrosses of Samgangbyeo, a BPH resistant indica variety carrying the Bph1 locus, with Nagdongbyeo, a BPH susceptible japonica variety. To identify genes that confer BPH resistance, we employed representational difference analysis (RDA) to detect transcripts that were exclusively expressed in one of our BPH resistant NIL, SNBC61, during insect feeding. The chromosomal mapping of the RDA clones that we subsequently isolated revealed that they are located in close proximity either to known quantitative trait loci or to an introgressed SSR marker from the BPH resistant donor parent Samgangbyeo. Genomic DNA gel-blot analysis further revealed that loci of all RDA clones in SNBC61 correspond to the alleles of Samgangbyeo. Most of the RDA clones were found to be exclusively expressed in SNBC61 and could be assigned to functional groups involved in plant defense. These RDA clones therefore represent candidate defense genes for BPH resistance.

Human rotavirus genotypes in hospitalized children, South Korea, April 2005 to March 2007.

Availability of new rotavirus vaccines highlights the need to maintain and enhance rotavirus strain surveillance. We collected stool samples from children with gastroenteritis admitted to eight hospitals in South Korea from April 2005 to March 2007. Of the 6057 samples collected, 1337 (22%) were positive for rotavirus by one of several antigen detection assays. G and P genotypes were identified for 1299 (97%) of rotavirus-positive specimens. G1P[8] (36%) was the most prevalent strain, followed by G3P[8] (16%), G4P[6] (8.9%) and G1P[6] (8.2%). G1P[8] was also the most prevalent strain in each hospital. Seasonal peaks of rotavirus infection were noted from November 2005 to April 2006 and January to March 2007. This large-scale surveillance study provides important insights into rotavirus genotype distribution and pattern changes in South Korea.

Genetic variation through Dissociation (Ds) insertional mutagenesis system for rice in Korea: progress and current status

A gene detection strategy using two-component Ac/Ds construct, with the mobile Ds transposon, has been developed to better understand gene functions in crops. Currently, 115,000 Ds insertion lines have been generated through the Ac/Ds gene trap system in Korea using japonica rice Dongjin as donor. Four hundred and thirty-seven mutants from 12,162 Ds-tagged lines were catalogued, including physiological and agronomic traits. Different traits were identified with distinct characteristics in terms of tillers, panicles, leaves, flowers, seed, chlorophyll content, and height. Culm and panicle length, number of panicles, and days to flowering of the Dongjin Ds population revealed high standard deviations compared with the donor cultivar. An evaluation of the Ds distribution on the chromosome revealed that 74.5% of the Ds were reinserted into gene-rich regions, making this Ac/Ds-mediated gene trap system useful in helping to gain an understanding of the function of genes and thus improve the gene-tagging system in rice.

Molecular Characterization and Physico-Chemical Analysis of a New Giant Embryo Mutant Allele (ge t ) in Rice (Oryza sativa L.)

The rice embryo is rich in lipid and protein bodies, bioactive chemicals such as dietary fiber, phytic acids, vitamin B and E, and gamma aminobutyric acid (GABA) than the endosperm. In this paper, we report a new giant embryo mutant,get, induced from somaclonal variation derived by anther culture in rice. Sequence analysis of Cytochrome P450 of the get mutant revealed thatget is a new allele of theGE gene with a single point mutation with substitution of amino acid, W395 to L395. The weight of theget mutant embryo was 3.7 times higher than normal embryo. Tocopherol and mineral content were also higher than the previously reported giant embryo rice variety, Keunnun. These results indicated that this new giant embryo rice (get) offers a promising source of genetic material in improving nutritional quality of rice especially tocopherol, essential minerals, and GABA.

Molecular tagging of the Bph1 locus for resistance to brown planthopper (Nilaparvata lugens Stål) through representational difference analysis

During brown planthopper (BPH) feeding on rice plants, we employed a modified representational difference analysis (RDA) method to detect rare transcripts among those differentially expressed in SNBC61, a BPH resistant near-isogenic line (NIL) carrying the Bph1 resistance gene. This identified 3 RDA clones: OsBphi237, OsBphi252 and OsBphi262. DNA gel-blot analysis revealed that the loci of the RDA clones in SNBC61 corresponded to the alleles of the BPH resistant donor Samgangbyeo. Expression analysis indicated that the RDA genes were up-regulated in SNBC61 during BPH feeding. Interestingly, analysis of 64 SNBC NILs, derived from backcrosses of Samgangbyeo with a BPH susceptible Nagdongbyeo, using a cleaved amplified polymorphic sequence (CAPS) marker indicated that OsBphi252, which encodes a putative lipoxygenase (LOX), co-segregates with BPH resistance. Our results suggest that OsBphi252 is tightly linked to Bph1, and may be useful in marker-assisted selection (MAS) for resistance to BPH.

Comparative analysis of physicochemicals and antioxidative properties of new giant embryo mutant, YR23517Acp79, in rice (Oryza sativa L.)

Nutritional and physicochemical properties of new giant embryo mutant rice (YR23517Acp79, YR) were analyzed. YR exhibited increased total protein (9.3±0.3%), lipid (3.7±1.1%), amino acid (663.28±1.9 mg/g), and mineral contents (Ca=284.0±6.2, Mg=1417.5±13.6 mg/kg). In YR brown rice four major physicochemicals, including gamma-aminobutyric acid (brown rice= 0.46±0.014 mg/g), γ-oryzanol (0.43±0.021 mg/g), vitamin B1 (6.42±0.3 mg/kg), and tocopherols (alpha= 2.68±0.1, beta=0.11±0.01, gamma=0.05±0.001 mg/100 g) increased in comparison to reported giant embryo (Keunnunbyeo, KB) and normal embryo rice (Ilmibyeo, IB). YR showed higher scavenging activities against 1,1-diphenyl-2-picrylhydrazyl (0.2 g/mL=57.1±2.25) and 2,2′-Azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (0.2 g/mL=50.2±1.45) radicals but also inhibited lipopolysaccharide-induced nitric oxide production without cytotoxicity. These results indicate YR is a high quality functional rice due to its high nutrition content and antioxidant effects of physicochemicals.

Large-scale screening of rice accessions to evaluate resistance to bakanae disease

Bakanae disease is an important fungal disease in the world. No rice (Oryza sativa L.) varieties have been found to be completely resistant to this disease. To facilitate accurate, uniform and simultaneous screening of many rice accessions, we developed an inoculation method for microconidia of Fusarium fujikuroi using a tissue embedding cassette and seedling tray. Standards for evaluating the inoculated rice seedlings as healthy or unhealthy were also established. The method was fast and reproducible for accurately evaluating resistance to bakanae disease in rice.

A Waxy Black Giant Embryo Earley Maturing Rice Variety ‘Nunkeunheugchal’

Nunkeunheugchal (registration No. 01-0001-2014-4), a black waxy giant embryo rice cultivar, was developed by the rice breeding team of National Institute of Crop Science (NICS), RDA in 2012. This cultivar was derived from the cross between ge and Josaengheugchal in 2004/2005 winter season, and selected by a promising line, YR25277-B-B-314-2, was selected and designated as the line of Milyang263 in 2009. The local adaptability test of Milyang263 was carried out at four locations from 2010 to 2012 and it was named as Nunkeunheugchal. This variety is a early maturity cultivar. It has 65 cm in culm length and 72 spikelets per panicle, and 1,000 grain-weight of brown rice is 17.8 g which is less than that of Josaengheugchal. This variety is resistant to leaf blast, but susceptible to bacterial blight, neck blast, virus disease and insect pest. The yield potential of Nunkeunheugchal was about 3.54 MT/ha as brown rice at ordinary fertilizer level in local adaptability test for three years. Nunkeunheugchal possesses benefits to rice consumers because of high amounts of GABA, anthocyanin, calcium and iron. This variety would be adaptable to the paddy field of middle and southern plain region of Korea.

Comparative studies on major nutritional components of black waxy rice with giant embryos and its rice bran

The concentration of nutrients in brown rice is mainly associated with embryo size. Various beneficial components have been purified from rice bran. Recently developed black waxy rice with a giant embryo (‘Milyang 263’, BGE), which is the get mutant of the GE gene, was selected and analyzed to produce high quality nutritional components. γ-Aminobutyric acid (GABA) content in BGE rice bran, one of the most important nutritional compounds in rice, showed a 10.6-fold increase (2.66±0.48 mg/g) compared to that of BGE brown rice (0.25±0.01 mg/g). In addition, brown rice and BGE rice bran showed enriched amylopectin (94.5±0.5 and 97.0±0.0%) and bioactive anthocyanin [Cy-3-G: 75.15±4.18 (brown rice), 82.97±0.81 (rice bran) and Pn-3-G: 1.52±0.50 (brown rice), 4.33±0.20 (rice bran); mg/100 g] contents. These results suggest that BGE rice bran can be used as an excellent raw material to efficiently produce high quality essential amino acids, cyanidin-3 glycoside-enriched anthocyanins, and GABA.

Development of Marker-free Transgenic Rice Expressing the Wheat Storage Protein, Glu-1Dy10, for Increasing Quality Processing of Bread and Noodles

Rice flour is used in many food products. However, dough made from rice lacks extensibility and elasticity, making it less suitable than wheat for many food products such as bread and noodles. The high-molecular weight glutenin subunits (HMW-GS) of wheat play a crucial role in determining the processing properties of the wheat grain. This paper describes the development of marker-free transgenic rice plants expressing a wheat Glu-Dy10 gene encoding the HMG-GS from the Korean wheat cultivar ‘Jokyeong’ using Agrobacterium-mediated co-transformation. Two expression cassettes, consisting of separate DNA fragments containing Glu-1Dy10 and hygromycin phosphotransferase II (HPTII) resistance genes, were introduced separately into Agrobacterium tumefaciens EHA105 for co-infection. Each EHA105 strain harboring Glu-1Dy10 or HPTII was infected into rice calli at a 3: 1 ratio of Glu-1Bx7 and HPTII. Among 290 hygromycin-resistant T0 plants, we obtained 29 transgenic lines with both the Glu-1Dy10 and HPTII genes inserted into the rice genome. We reconfirmed the integration of the Glu-1Dy10 gene into the rice genome by Southern blot analysis. Transcripts and proteins of the Glu-1Dy10 in transgenic rice seeds were examined by semi-quantitative RT-PCR and Western blot analysis. The marker-free plants containing only the Glu-1Dy10 gene were successfully screened in the T1 generation.