Seok-Cheol Suh

Application of two bicistronic systems involving 2A and IRES sequences to the biosynthesis of carotenoids in rice endosperm.

Coordination of multiple transgenes is essential for metabolic engineering of biosynthetic pathways. Here, we report the utilization of two bicistronic systems involving the 2A sequence from the foot-and-mouth disease virus and the internal ribosome entry site (IRES) sequence from the crucifer-infecting tobamovirus to the biosynthesis of carotenoids in rice endosperm. Two carotenoid biosynthetic genes, phytoene synthase (Psy) from Capsicum and carotene desaturase (CrtI) from Pantoea, were linked via either the synthetic 2A sequence that was optimized for rice codons or the IRES sequence under control of the rice globulin promoter, generating PAC (Psy-2A-CrtI) and PIC (Psy-IRES-CrtI) constructs, respectively. The transgenic endosperm of PAC rice had a more intense golden color than did PIC rice, demonstrating that 2A was more efficient than IRES in coordinating gene expression. The 2A and IRES constructs were equally effective in driving transgene transcription. However, immunoblot analysis of CRTI, a protein encoded by the downstream open reading frame of the bicistronic constructs, revealed that 2A was ninefold more effective than IRES in driving translation. The PAC endosperms accumulated an average of 1.3 μg/g of total carotenoids, which was ninefold higher than was observed for PIC endosperms. In particular, accumulation of β-carotene was much higher in PAC endosperms than in PIC endosperms. Collectively, these results demonstrate that both 2A and IRES systems can coordinate the expression of two biosynthetic genes, with the 2A system exhibiting greater efficiency. Thus, the 2A expression system described herein is an effective new tool for multigene stacking in crop biotechnology.

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.

Compositional comparative analysis between insect-resistant rice (Oryza sativa L.) with a synthetic cry1Ac gene and its non-transgenic counterpart

Composition analysis of genetically modified crops is an important consideration in the assessment of food safety. Agb0101 (Oryza sativa L. cv. Nakdongbyeo) developed in Korea is a form of insect-resistant rice that contains a synthetic truncated cry1Ac gene isolated from Bacillus thuringiensis (Bt), and demonstrates high resistance to rice leaf folder under field conditions. Nutrients, anti-nutritive components, and secondary metabolites of Agb0101 were analyzed and compared with those of its non-transgenic counterpart. The amounts of proximates, amino acids, fatty acids, minerals, vitamins, trypsin inhibitors, phytic acid, and ferulic acid in brown rice from Agb0101 were comparable to those of its non-transgenic counterpart. Statistical comparisons to test for equivalence showed that all the analyzed components in the insect-resistant rice plants were substantially equivalent to those of its non-transgenic counterpart. Furthermore, most of the measured values from Agb0101 were within the range of values reported for other commercial rice varieties.

A Ds-insertion mutant of OSH6 (Oryza sativa Homeobox 6) exhibits outgrowth of vestigial leaf-like structures, bracts, in rice

OSH6 (Oryza sativa Homeobox6) is an ortholog of lg3 (Liguleless3) in maize. We generated a novel allele, termed OSH6-Ds, by inserting a defective Ds element into the third exon of OSH6, which resulted in a truncated OSH6 mRNA. The truncated mRNA was expressed ectopically in leaf tissues and encoded the N-terminal region of OSH6, which includes the KNOX1 and partial KNOX2 subdomains. This recessive mutant showed outgrowth of bracts or produced leaves at the basal node of the panicle. These phenotypes distinguished it from the OSH6 transgene whose ectopic expression led to a “blade to sheath transformation” phenotype at the midrib region of leaves, similar to that seen in dominant Lg3 mutants. Expression of a similar truncated OSH6 cDNA from the 35S promoter (35S::ΔOSH6) confirmed that the ectopic expression of this product was responsible for the aberrant bract development. These data suggest that OSH6-Ds interferes with a developmental mechanism involved in bract differentiation, especially at the basal nodes of panicles.

Event-specific detection system of stacked genetically modified maize by using the multiplex-PCR technique

Stacked genetically modified (GM) crops are becoming popular for their enhanced production efficiency and improved functional properties. In this study, we developed an event-specific PCR method for simple qualitative detection of stacked events combining more than 2 transgenic traits. Ten primer sets were designed, including 9 that were event-specific and 1 that was specific for a maize endogenous gene. Five event-specific multiplex-PCR systems were built, based on the main type of stacked GM events approved in Korea. Multiplex PCR was performed with mixtures of template DNA extracted from certified reference materials. PCR amplicons (3 or 4 by type) of expected sizes and mutually similar intensities were detected. The limit of detection was approximately 0.1%(v/v) for stacked GM maize in all event-specific PCRs. This method may be useful for the specific detection and monitoring of stacked GM maize lines and individual parent GM maize lines, by effectively distinguishing genestacked events.

Molecular biological characteristics and analysis using the specific markers of leaf folder-resistant GM rice

Abstract In recent years, several genetically modified (GM) crops have been developed worldwide through the recombinant DNA technology and commercialized by various agricultural biotechnological companies. Commercialization of GM crops will be required the assesment of risks associated with the release of GM crops. In advance of the commercial release of GM crops, developer should submit the several information on GM crops for approval. In this study, we carried out to provide the molecular data for the risk assessment of GM rice containing insect-resistant gene, modified Cry1Ac (CryIAc1). Through the molecular analysis with CryIAc1 induced GM rice, we confirmed the steady integration and expression of transgene, the transgene copy number, the adjacent region sequences of inserted gene into rice genome, and the transgene stability in progenies. For the qualitative PCR detection methods, specific primer pairs were designed on the basis of integration sequences, and construct- and event-specific detection markers were developed for leaf folder-resistant rice, Cr7-1 line. From these results, we demonstrated that the molecular data and the PCR detection methods of leaf folder- resistant GM rice could be acceptable to conduct the biosafety and environment risk assessment.

Policosanol Content and Composition of Korean Rice (Oryza sativa L.) Cultivars

ABSTRACT Policosanols (PCs) are a group of long-chain alcohols that have been reported to have many beneficial physiological activities. In this study, the total content and composition of PCs in 15 rice (Oryza sativa L.) cultivars from Korea were characterized by gas chromatography–time-of-flight mass spectrometry. This method proved to be sufficiently precise and accurate with respect to the degree of endogenous biological variability found in the rice samples. Octacosanol (C28) and triacontanol (C30) were the major components of PCs in all cultivars. In addition, there were positive correlations among the determined PC contents. Given its high PC content, the Heughyangbyeo cultivar may appear to be a good candidate for future breeding programs.

Event-specific qualitative and quantitative polymerase chain reaction methods for detection of insect-resistant genetically modified Chinese cabbage based on the 3′-junction of the insertion site

Transgenic Chinese cabbage 416-3 was developed in Korea by a transformation event involving modified insectresistant gene (cry1Ac1). To monitor unintended release of genetically modified (GM) Chinese cabbage in the future, as well as to meet GM-labeling requirements, the development of a reliable method for detection of GM cabbage is requisite. To develop qualitative and quantitative polymerase chain reaction methods for the insect-resistant GM Chinese cabbage, a cytosolic glutathione reductase (BcgGR1) gene was used as the endogenous reference gene. Primer pairs CGR-1/-2, amplifying the Chinese cabbage endogenous gene, yielded an expected amplicon of 121 bp, whereas no amplified product was observed when DNA samples from seven non-cabbage plants were used as templates. The event-specific primer pairs amplifying the junction site between the endogenous genome sequence and the transferred DNA of GM event 416-3, produced amplicons of desired size by qualitative polymerase chain reaction (PCR) assay. An eventspecific quantitative PCR detection method was established using a TaqMan probe and a standard plasmid as a reference molecule, which contained both endogenous and event-specific sequences. For the validation of this method, three different compositions of w/w mixed samples (containing transgenic DNA at 5, 1, and 0.5% of total DNA in the control samples) were quantified. The precision, expressed as standard deviation (SD) and relative standard deviations (RSD), deviated by 0.03–0.26% and 4.75–8.06%, respectively. These results clearly demonstrate that the PCR methods developed herein can be used for event-specific qualitative and quantitative testings of insect-resistant GM Chinese cabbage.

Effect of cultivar and ascorbic acid on in vitro shoot regeneration and development of bombardment-mediated plastid transformation of tomato (Lycopersicon esculentum)

Abstract Eighteen cultivars of tomato were tested for their regeneration response. Lycopersicon esculentum cv. 2001- 58 showed a very high frequency of regeneration (93%). We evaluated the effect of two compounds with known antio-xidant activity (ascorbic acid and cystein). The use of ascorbic acid (200 - 300 μM/L) has a positive effect on s hoot regeneration. To develope a system for plastid transfor-mation in tomato via homologous recombination, we con-structed the tomato plastid expression vector (pKRT22-AG) harboring 2.2 kb flanking sequences cloned from intact plastid genome and gfp gene. To investigate the factors affecting the delivery system of the pKRT22-AG into chloroplast using bombardment, We assessed the optimal DNA concentration, gold particle volume and target distance. Expression of the GFP protein was observed within chloroplast on protoplast of cotyledon explant by confocal laser scanning microscopy, which indicates that the protocol developed in this study be useful for the production of plastid transgenic plants in tomato.

Qualitative and quantitative PCR detection of insect-resistant genetically modified rice Agb0101 developed in korea

살충성 유전자 mcrylAcl을 포함하고 있는 해충저항성 유 전자변형 （GM) 벼 Agb0101이 국내에서 개발되었다． 향후 Agb0101 벼의 환경방출에 따른 모니터링과 이력추적을 위해서는 신뢰성 있는 검출방법의 개발이 필요하다． 따라서， 본 연구에서 해충저항성 GM벼의 사후 안전관리를 위한 정성적 및 정량적 PCR 검정 방법을 개발하였다． 벼 녹말분지효소 유전자 RBE4를 PCR 분석의 내재유전자로 사용하였고， 이의 primer쌍 RBEgh- 1/ - 2는 101bp의 PCR 증폭산물을 형성하였다． 정성 PCR 분석을 위해서 삽입된 T- DNA를 바탕으로 특이 Primer를 제작하였고， 이벤트 특이적 검출 primer의 경우 Agb0101의 도입유전자 및 벼 염색체 DNA 사이의 5``또는3``인접염기부위를 정확하게 특이적으로 PCR 증폭하였다． 반면， 대조구인 각종 작물， 국 내 벼 품종 및 Agb0101과 동일 형질전환 벡터를 갖는 해 충 저 항성 벼 에 서 는 어 떠 한 PCR 증폭산물도 형성하지 않았다. 표준물질로써 내재유전자 및 이벤트 특이적 단편으로 제조된 pRBECrR을 이용한 real- time PCR 분석에 의해 서 정량한계 （LOQ） 가 10 copies 농도의 범위인 것으로 확인되었고, 이의 유효성을 검증하기 위하여 상이한 농도 의 Agb0101시료 （1O, 5, 3 및 I%를 real-time PCR 분석하여 정량검정에 대한 표준편차 및 상대표준편차가 각각 0. 06~0.40 및 3.80, 7.01％ 의 낮은 범위에 포함되는 것을 확 인할 수 있었다． 이들 결과로 본 연구에서 개발된 정성 및 정량 PCR 검정 방법이 해충저항성 GM벼 Agb0101의 모니터링 및 이력추적에 효과적으로 이용될 수 있을 것으로 본다.