Woon-Ha Hwang

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.

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.

Development of Marker-free Transgenic Rice for Increasing Bread-making Quality using Wheat High Molecular Weight Glutenin Subunits (HMW-GS) Gene

High-molecular weight glutenin subunits (HMW-GS) have been shown to play a crucial role in determining the processing properties of the wheat grain. We have produced marker-free transgenic rice plants containing a wheat Glu-1Bx7 gene encoding the HMG-GS from the Korean wheat cultivar ‘Jokyeong’ using the Agrobacterium-mediated co-transformation method. The Glu-1Bx7-own promoter was inserted into a binary vector for seed-specific expression of the Glu-1Bx7 gene. Two expression cassettes comprised of separate DNA fragments containing only Glu-1Bx7 and hygromycin phosphotransferase II (HPTII) resistance genes were introduced separately to the Agrobacterium tumefaciens EHA105 strain for co-infection. Each EHA105 strain harboring Glu-1Bx7 or HPTII was infected to rice calli at a 3:1 ratio of Glu-1Bx7 and HPTII, respectively. Then, among 216 hygromycin-resistant T0 plants, we obtained 24 transgenic lines with both Glu-1Bx7 and HPTII genes inserted into the rice genome. We reconfirmed integration of the Glu-1Bx7 gene into the rice genome by Southern blot analysis. Transcripts and proteins of the wheat Glu-1Bx7 were stably expressed in the rice T₁ seeds. Finally, the marker-free plants harboring only the Glu-1Bx7 gene were successfully screened at the T₁ generation.

Emergence Characteristics of Weedy Rice Collected in South Korea

In order to provide basic data for efficient control of weedy rice, we analyzed emergence rate of 100 weedy rice genetic resources collected in South Korea according to growth temperature and soil burial depth. Analyzing of emergence rate using low dormancy weedy rice genetic resources, emergence was increased at 12 and 14°C of mean temperature condition. When calculating the effective accumulated temperature above 10°C, emergence rate increased 0.6% and 0.5% in 1 cm and 3 cm of soil depth, respectively according to increase of 1°C. However it reduced as 0.28% in 5 cm of soil depth condition. Analyzing of emergence rate using high dormancy weedy rice, red rice showed 55%, 46%, 41% of emergence rate in 1 cm, 3 cm and 5 cm of soil depth condition, respectively. However those of white rice decreased as 10%, 8% and 5.7% in 1 cm, 3 cm and 5 cm of soil depth condition, respectively. Relative emergence, assuming the final emergence rate as 100%, reached 80%, 90% and 100% when effective accumulated temperature was 83-112°C, 100-123°C, 148-160°C respectively.

Selection of the Korean Rice Cultivars Having Adaptable Heading Characters in Subtropical Regions

[Introduction] Japonica rice is recognized as the premium rice compared to Indica rice in tropical region especially in Philippines. Therefore development of adaptive Japonica rice variety in tropical region has been actively conducting to increase income of local farmers in the tropical regions. Here we tried to investigate the basic vegetative phase and temperature sensitivity during sensitive phase among Korean major cultivars to recommend the Korean rice cultivar which shows the suitable heading characters in tropical region then help to develop adaptive rice cultivars in tropical region.

Generation of Transgenic Rice without Antibiotic Selection Marker through Agrobacterium-mediated Co-transformation System

Development of transgenic plant increasing crop yield or disease resistance is good way to solve the world food shortage. However, the persistence of marker genes in crops leads to serious public concerns about the safety of transgenic crops. In the present paper, we developed marker-free transgenic rice inserted high molecular-weight glutenin subunit (HMW-GS) gene (Dx5) from the Korean wheat cultivar ‘Jokyeong’ using Agrobacterium-mediated co-transformation method. Two expression cassettes comprised of separate DNA fragments containing only the Dx5 and hygromycin resistance (HPTII) genes were introduced separately into Agrobacterium tumefaciens EHA105 strain for co-infection. Each EHA105 strain harboring Dx5 or HPTII was infected into rice calli at a 3: 1 ratio of EHA105 with Dx5 gene and EHA105 with HPTII gene expressing cassette. Then, among 66 hygromycin-resistant transformants, we obtained two transgenic lines inserted with both the Dx5 and HPTII genes into the rice genome. We reconfirmed integration of the Dx5 and HPTII genes into the rice genome by Southern blot analysis. Wheat Dx5 transcripts in T1 rice seeds were examined with semi-quantitative RT-PCR. Finally, the marker-free plants containing only the Dx5 gene were successfully screened at the T1 generation. These results show that a co-infection system with two expression cassettes could be an efficient strategy to generate marker-free transgenic rice plants.

Phosphate uptake and growth characteristics of transgenic rice with phosphate transporter 1 (OsPT1 ) gene overexpression under high phosphate soils

Farmers have used phosphate fertilizer to provide sufficient yields. However, overuse of phosphorus accumulate in soil and causes soil and water pollution. We evaluated the phosphate acquisition and growth characteristics of OsPT1 transgenic rice (OsPT1-OX, over-expressing the high affinity phosphate transporter 1) in high phosphate soils with different level of nitrogen fertilizer treatment to investigate its removal ability of excessive phosphate from soil. OsPT1-OX had shorter culm length but more tillers than those of wild-type plants in each soil conditions. Phosphate content per dry weight of OsPT1-OX was 1.8 times higher than that of wild-type under control fertilizer treated conditions. Although the dry weight of OsPT1-OX was not different from that of wild-type plants, whole plant phosphate content was 1.7 times higher than that of wild-type plants under control fertilizer conditions. Tiller number and phosphate content per dry weight of wild-type plants increased following high levels of phosphate application, but did not change following additional nitrogen application. Tiller number and phosphate content per dry weight of OsPT1-OX did not also change under the high phosphate condition, but increased following nitrogen application under similar conditions. Whole plant phosphate content was also highest under high nitrogen and high phosphate application conditions. These results suggest that OsPT1-OX may reduce phosphate content in soils containing excess phosphate and may be further effective under high nitrogen condition. Key words : Phosphate content, fertilizer treatment, phosphate transporter, rice, soil.

Molecular re-confirmation and floral characteristics of drooping leaf (DL) mutants generated by insertional mutagenesis in rice

Transposon tagging and insertional mutagenesis provide one of the most powerful tools in gene function studies. Here, we report a comparison between two novel drooping leaf (DL) mutants from transposon and T-DNA insertion lines of rice. DL is distinct from well-known ABC genes and a member of the YABBY gene family, and it is closely related to the CRABS CLAW (CRC) gene of Arabidopsis thaliana. Based on phenotypic analysis, DL regulated midrib formation by promoting cell proliferation in the central region of rice leaf and was necessary for the specification of carpel identity. We identified two DL mutants by screening the Ac/Ds and T-DNA insertional mutant pool of rice. Flanking sequence tag analysis indicated that both Ds and T-DNA segments were inserted in the promoter region at 3.4 kbs and 5.4 kb upstream, respectively, of the previously known OsYABBY domain. Interestingly, the progenies of DL lines of two different pools showed various degrees of leaf drooping and abnormal carpel formation. Flower structures revealed that there were more than two stigmas with normal stamens and pistils per panicle in the Ds-induced mutants. However, T-DNA induced mutant had extra stamens with staminoid carpels. These results indicate that the promoter region of DL plays an important function in regulating anther and carpel formation.