Yeon-Jae Hur

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.

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.

Agrobacterium-Mediated Transformation of Phalaenopsis by Using Protocorm-Like Body

Agrobacterium tumefaciens-mediated transformation procedure for the phalaenopsis orchid, established by using Protocorm-like bodies (PLBs), was aimed at the introduction of target genes into individuals with divergent genetic backgrounds. PLBs obtained from the axillary bud of a peduncle were maintained on a hyponex medium supplemented with 1 g/l of activated charcoal, 30 g/l of sucrose and 0.1 mg/l thiamine. The multiplication rate of PLBs was about 90% in case of subculture PLBs to be cut transversely into 1/3 part from top position. The PLBs were inoculated with Agrobacterium strain EHA105 harboring both -glucuronidase (GUS) and hygromycin-resistant genes for 20 minutes after dipping treatment. Transformation efficiency was the highest with a Agrobacterium culture medium and dipping treatment of O.D. 0.8. Newly induced PLBs were put on selection medium containing 1 mg/l hygromycin for 2 months. Hygromycin-resistant phalaenopsis plants that regenerated after the selection culture of PLBs showed histochemical blue staining due to GUS. Transgene integration of the hygromycin-resistant plants was confirmed by PCR and Southern blot using GUS specific primers and probe.