• 원예과학기술지
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• 제31권1호
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• pp.72-79
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• 2013

Inactivation of the gene coding for dihydroflavonol 4-reductase (DFR) is responsible for the color difference between red and yellow onions (Allium cepa L.). Two inactive DFR-A alleles, DFR-$A^{PS}$ and DFR-$A^{DEL}$, were identified in our previous study. A functional marker was developed on the basis of the premature stop codon that inactivated the DFR-$A^{PS}$ allele. A derived cleaved amplified polymorphic sequences (dCAPS) primer was designed to detect the single nucleotide polymorphism, an A/T transition, which produced the premature stop codon. Digested PCR products clearly distinguished the homozygous and heterozygous red $F_2$ individuals. Meanwhile, to develop a molecular marker for detection of the DFR-$A^{DEL}$ allele in which entire DFR-A gene was deleted, genome walking was performed and approximately 3 kb 5' and 3' flanking sequences of the DFR-$A^R$ coding region were obtained. PCR amplification using multiple primers binding to the extended flanking regions showed that more of the extended region of the DFR-A gene was deleted in the DFR-$A^{DEL}$ allele. A dominant simple PCR marker was developed to identify the DFR-$A^{DEL}$ allele using the dissimilar 3' flanking sequences of the DFR-A gene and homologous DFR-B pseudogene. Distribution of the DFR-$A^{PS}$ and DFR-$A^{DEL}$ alleles in yellow onion cultivars bred in Korea and Japan was surveyed using molecular makers developed in this study. Results showed predominant existence of the DFR-$A^{PS}$ allele in yellow onion cultivars.

• Journal of Microbiology and Biotechnology
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• 제12권1호
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• pp.106-113
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• 2002

One-hundred and twenty-four trimethoprim-resistant Shigella sonnei isolates extracted in Korea during the last two decades were investigated for their epidemiological relationship and mechanisms of resistance to trimethoprim. The S. sonnei isolates were distributed into two groups by three different epidemiological tools: biotyping, antibiogram, and pulsed-field gel electrophoresis. One group contained the isolates from the 1980s and the other group included the isolates from the 1990s. The geometric mean MICs of trimethoprim in S. sonnei isolates from the 1980s and 1990s were found to be $672.9{\mu}g/ml\;and\;>2,048{\mu}g/ml$, respectively. Trimethoprim resistance was associated with dfrA5, dfrA12, and dfrA13 genes in the isolates from the 1980s, dfrA1, dfrA5, and dfrA12 in the isolates from 1991, and dfrA1 and dfrA12 in the isolates from 1992 to 1999. The dfrA1 gene was located downstream of the intI2 gene in Tn7, which was located on chromosome. Some dfrA12 genes were found as gene cassettes in the class 1 integron. The dfrA5 and dfrA13 genes were located on conjugative plasmids. These results suggested that a clonal change occurred in S. sonnei isolates in Korea during the last two decades and that dfr genes located on different transposable genetic elements had gradually changed.

• Journal of Applied Biological Chemistry
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• 제49권3호
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• pp.75-81
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• 2006

A full-length cDNA encoding dihydroflavonol 4-reductase (st-dfr) of potato was isolated by rapid amplification of cDNA ends, and their expression was investigated from purple-fleshed potato (Solanum tuberosum L. cv. Jashim). The st-dfr exists as a member of a small gene family and its transcripts was abundant in the order of tuber flesh, stem, leaf, and root. The expressions of st-dfr gene were light inducible and cultivar dependant. Transgenic potato plants harboring antisense st-dfr (AS-DFR) sequences were analyzed. The accumulation of mRNA was nearly completely inhibited as a result of introducing an AS-DFR gene under the control of the 35S CaMV promoter into the red tuber skin Solanum tuberosum L. cv. Desiree. The anthocyanin content of the tuber peels of the transgenic lines was dramatically decreased by up to 70%. The possible production of flavonols in the peels of AS-DFR transgenic potatoes was discussed.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2017년도 9th Asian Crop Science Association conference
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• pp.163-163
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• 2017

A deletion analysis of the Oryza sativa dihydroflavonol reductase (DFR) promoter defined a 25 bp region (-386 to -362) sufficient to confer pericarp-specific expression of ${\beta}$ -glucuronidase(GUS) reporter gene in transgenic rice. Site-specific mutagenesis of these conserved sequences and subsequent expression analysis in calli which transiently expressed the mutated promoter::GUS gene showed that both bHLH (-386 to -381) and Myb (-368 to -362) binding sites in the DEL3 (-440 to 70) promoter were necessary for complete expression of the GUS gene including the tissue-specific expression of DFR::GUS gene. The GUS gene was expressed well in the mutated Myb (-368 to -362) binding site, but not as strong as in normal condition, implying that the Myb is also necessary to express GUS gene fully. Also, we found the non-epistatic relation between Rc and DFR. There were no changes of expression patterns GUS under the Rc and rc genotypes. Thus, DFR expression might be independent of the presence of functional Rc gene and suggested that Rc and Rd (DFR) share the same pathway controlling the regulation of flavonoid synthesis but not a direct positive transcriptional regulator of DFR gene.

• Journal of Microbiology and Biotechnology
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• 제24권7호
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• pp.1008-1013
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• 2014

The use of antimicrobial agents for additives or therapeutics is strongly associated with a prevalence of antimicrobial resistance in commensal Enterobacteriaceae. We aimed to characterize integrons in Enterobacteriaceae isolates obtained from chicken cecums in Korea. Moreover, the correlation between integron gene cassettes and antimicrobial resistance was also investigated. A total of 90 isolates the belonged to Enterobacteriaceae were recovered from chickens grown at Gyeongsang and Chungcheong provinces in Korea. Antimicrobial susceptibility tests were performed by the disk diffusion method. PCR and DNA sequencing were also performed to characterize the gene cassette arrays of the integrons. Of the 90 Enterobacteriaceae isolates tested, 39 (43.3%) and 10 (11.1%) isolates carried class 1 and 2 integrons, respectively. Whereas the class 2 integron did not contain gene cassettes, the class 1 integrons carried seven different gene cassette arrays. The class 1 integrons harbored genes encoding resistant determinants to aminoglycosides (aadA1, aadA2, and aadA5), trimethoprim (dfrA1, dfrA12, dfrA17, and dfrA32), lincosamides (linF), and erythromycin (ereA). Moreover, the presence of a class 1 integron was significantly related to a high resistance rate of antimicrobial agents, such as spectinomycin and trimethoprim. We confirmed that diverse class 1 integrons were widely distributed in Enterobacteriaceae isolates from chickens and directly contributed to the resistance to diverse antimicrobial agents in Korea.

• Journal of Plant Biotechnology
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• 제37권1호
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• pp.89-95
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• 2010

Dihydroflavonol 4-reductase(DFR)는 flavonoid 생합성 경로의 가장 중심부에 작용하는 효소로 2R,3R-trans-dihydroflavonols로부터 leucoanthocyanidins 으로의 변환을 촉매한다. 본 연구에서는 색소유전자의 전이를 통하여 새로운 색소발현체계를 가진 품종을 육종하기 위한 기초연구로 안개초 (Gypsophila paniculata L.)의 꽃봉오리로부터 cDNAlibrary를 합성하였고 카네이션의 DFR 유전자를 probe로 사용하여 anthocyanin 합성경로의 중요 효소의 하나인 DFR 유전자를 분리하였다. 염기서열분석을 수행하여 분리유전자의 크기가 1279 bp이며 이 중 coding region은 1063 bp임을 확인하였다. 이미 밝혀진 다른 식물체의 DFR 유전자와 서로 염기서열의 일치성을 비교해 본 결과 Cheddar pink, 카네이션, 양배추, 개나리, 페튜니아, cup flower, 장미, 과꽃 및 거베라에서 각각 62% 이상을 나타내었다. 분리유전자의 발현을 확인하기 위하여 Northern blot 분석 및 인위적으로 기내에서의 transcription과 translation을 수행하였고, 분리한 유전자의 효소활성을 측정해 본 결과 leucopelargonidin의 작은 peak를 확인하였다. Southern blot 분석 결과 안개초의 DFR 유전자는 다른 대부분의 식물체와 유사하게 한 개가 존재함을 확인하였다.

• 원예과학기술지
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• 제35권3호
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• pp.323-332
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• 2017

Homology-specific transcriptional and post-transcriptional silencing, an intrinsic mechanism of gene regulation in most eukaryotes, can be induced by anti-sense, co-suppression, or hairpin-based double-stranded RNA. Hairpin-based RNA interference (RNAi) has been applied to analyze gene function and genetically modify crops. However, RNAi vector construction usually requires high-cost cloning steps and large amounts of time, or involves methods that are protected by intellectual property rights. We describe a more effective method for generating intron-spliced RNAi constructs. To produce intron-spliced hairpin RNA, an RNAi cassette was ligated with the first intron and splicing sequences of the Brassica rapa ssp. pekinensis histone deacetylase 1 gene. This method requires a single ligation of the PCR-amplified target gene to SpeI-NcoI and SacI-BglII enzyme sites to create a gene-specific silencing construct. We named the resulting binary vector system pKHi and verified its functionality by constructing a vector to silence DIHYDROFLAVONOL 4-REDUCTASE (DFR), transforming it into tobacco plants, and confirming DFR gene-silencing via PCR, RT-qPCR, and analysis of the accumulation of small interfering RNAs. Reduction of anthocyanin biosynthesis was also confirmed by analyzing flower color of the transgenic tobacco plants. This study demonstrates that small interfering RNAs generated through the pKHi vector system can efficiently silence target genes and could be used in developing genetically modified crops.

• 식물조직배양학회지
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• 제25권5호
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• pp.341-346
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• 1998

색소유전자의 전이를 통하여 새로운 색소발현체계를 가진 품종을 육종하기 위한 기초연구로 stock (Matthiola incana R. Br.)의 꽃봉오리로부터 cDNA-library를 합성하였고 screening을 통하여 anthocyanin 합성경로의 중요효소의 하나인 DFR (dihydroflavonol 4-reductase) 유전자를 분리하였다. 염기서열분석을 수행하여 분리유전자의 크기가 1450bp 이며 이중 coding region은 1029 bp 임을 확인하였다. 이미 밝혀진 다른 식물체의 DFR 유전자와 서로 염기서열의 일치성을 비교해 본 결과 외자엽식물인 옥수수와 보리와는 각각 61%를 보였으며, 쌍자엽식물인 페튜니아, 금어초, 거베라, 과꽃 그리고 카네이션 등 과는 66%-67%의 일치성을 나타내었다. 아울러 염기서열의 G/C 함량분석을 통하여 쌍자엽식물의 G/C 함량은 외자엽식물의 그것에 비해 매우 낮은 수치를 나타내었다. 분리유전자의 발현을 확인하기 위하여 인위적으로 기내에서의 전사와 해석을 수행한 결과 42-44 kd 크기의 단백질을 확인하였다. Southern blot 분석의 결과 DFR 유전자는 stock의 genome에 다른 대부분의 식물체와 유사하게 한 개가 존재하며 야생종과 돌연변이종의 stock을 분리 DFR 유전자를 probe 로 Northern blot 분석을 수행하여 돌연변이종인 lineK17b가 DFR 돌연변이임을 확인하였다.

• 한국식물생명공학회:학술대회논문집
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• 한국식물생명공학회 2005년도 추계학술대회 및 한일 식물생명공학 심포지엄
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• pp.3-8
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• 2005

Torenia hybridacv. Summerwave Blue and Violet mainly produce delphinidin. Down regulation of their flavonoid 3'-hydroxylase and flavonoid 3',5'-hydroxylase (F3'5'H) genes and over expression of rose or pelargonium dihydroflavonol 4-reductase (DFR) cDNA yielded pelargonidin-based bright pink flowers. Nierembergia cv. Fairybells lack pink color as they produced only delphinidin and flavonols. Pelargonidin-based pink flowers were achieved by down regulation of F3'5'H and flavonol synthase genes and over expressing rose DFR cDNA. Introduction of petunia F3'5'H and DFR cDNAs into white carnations deficient in DFR activity produced violet carnations, which arc now commercialized in the USA, Canada, Australia, Europe and Japan. Introduction of pansy F3'5'H and iris DFR cDNAs and down regulation of rose DFR gene produced rose flowers which accumulates delphinidin imparting novel violet color.

• Plant Biotechnology Reports
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• 제3권1호
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• pp.95-101
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• 2009

Tea leaves are major source of catechins—antioxidant flavonoids. Dihydroflavonol 4-reductase (DFR, EC 1.1.1.219) is one of the important enzymes that catalyzes the reduction of dihydroflavonols to leucoanthocyanins, a key ''late'' step in the biosynthesis of catechins. This manuscript reports characterization of DFR from tea (CsDFR) that comprised 1,413 bp full-length cDNA with ORF of 1,044 bp (115-1,158) and encoding a protein of 347 amino acids. Sequence comparison of CsDFR with earlier reported DFR sequences in a database indicated conservation of 69-87% among amino acid residues. In silico analysis revealed CsDFR to be a membrane-localized protein with a domain (between 16 and 218 amino acids) resembling the NAD-dependent epimerase/dehydratase family. The theoretical molecular weight and isoelectric point of the deduced amino sequence of CsDFR were 38.67 kDa and 6.22, respectively. Upon expression of CsDFR in E. coli, recombinant protein was found to be functional and showed specific activity of 42.85 nmol $min^{-1}$ mg $protein^{-1}$. Expression of CsDFR was maximum in younger rather than older leaves. Expression was down-regulated in response to drought stress and abscisic acid, unaffected by gibberellic acid treatment, but up-regulated in response to wounding, with concomitant modulation of catechins content. This is the first report of functionality of recombinant CsDFR and its expression in tea.