Tae-Heon Kim

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.

Drought-tolerant QTL qVDT11 leads to stable tiller formation under drought stress conditions in rice

Drought is an important limiting factor for rice production, but the genetic mechanisms of drought tolerance is poorly understood. Here, we screened 218 rice varieties to identify 32 drought-tolerant varieties. The variety Samgang exhibited strong drought tolerance and stable yield in rain-fed conditions and was selected for further study. To identify QTLs for drought tolerance, we examined visual drought tolerance (VDT) and relative water content (RWC) phenotypes in a doubled haploid (DH) population of 101 individuals derived from a cross between Samgang and Nagdong (a drought-sensitive variety). Three QTLs from Samgang were identified for VDT and explained 41.8% of the phenotypic variance. In particular, qVDT11 contributed 20.3% of the phenotypic variance for RWC. To determine QTL effects on drought tolerance in rain-fed paddy conditions, seven DH lines were selected according to the number of QTLs they contained. Of the drought-tolerance-associated QTLs, qVDT2 and qVDT6 did not affect tiller formation, but qVDT11 increased tiller number. Tiller formation was most stable when qVDT2 and qVDT11 were combined. DH lines with both of these drought-tolerance-associated QTLs exhibited the most stable tiller formation. Together, these results suggest that qVDT11 is important for drought tolerance and stable tiller formation in rain-fed paddy fields.

Genotype analysis of genes involved in increasing grain number per panicle in rice germplasm

벼 수량성 증진을 위하여 수당립수 증진 유전자로 보고된 5종의 유전자에 대한 분자표지를 검정하고 유전자원 479점에서 이들의 유전자에 대한 유전형을 검정하였다. 판독이 용이한 Gn1a 및 DEP1, Apo1 유전자의 In/del 분자표지를 각각 개발하였고 Ghd7과 Nal1 유전자에 대하여서는 기존 보고된 SNP 분자표지를 이용하여 편리성을 검정하였다. 이들 분자표지는 아가로즈젤에서 각각의 유전형 판독이 용이하기에 벼 수량성 향상을 위한 분자육종에 적용이 가능할 것으로 기대되었다. 유전자원 479점에서 수당립수 증진 유전자 5종의 유전형을 분석하였을 때 총 13개의 haplogype으로 분류되었다. 대부분의 Indica 품종과 Japonica 품종은 haploptype 1과 haplotype 13에 속하였다. 나머지 haplotype에 속한 55점의 유전자원은 수당립수 증진 유전자에 대한 유전다양성을 보유한 자원으로 유전체 분석 등을 위한 핵심집단으로 활용할 수 있을 것으로 판단되었다. 유전자원 396점의 수량구성요소를 비교하였을 때, Nal1을 제외한 4종의 수당립수 증진 유전자의 수량증진 대립유전자형에서 이삭 수가 0.6 ~ 0.8개/주 감소하였으나 수당립수는 이삭당 27 ~ 29개 증진되었다. Nal1 유전자는 유전적 배경에 따라 효과가 다르게 나타나며, Nal1-japonica 대립유전자형의 수당립수 증진 효과보다 Nal1-indica 대립유전자형이 감소효과가 큰 것으로 추측되었다. 앞으로 본 논문에서 검정된 수당립수 증진 분자표지 5종과 유전자원의 유전형을 정보를 바탕으로 벼 수량성 증진 육종에 활용하고자 한다.