• Applied Biological Chemistry
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• v.36 no.6
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• pp.533-538
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• 1993

The Wx protein, known as starch synthase or starch glucosyl transferase (E.C. 2.4.1.11), is responsible for the amylose synthesis. In an effort to explain the mechanism of amylose biosynthesis, the starch synthase known as Wx protein was identified by analyzing the various wx rice mutants with SDS-PAGE of proteins extracted from rice starch. Finally, the 66 kDa protein was purified by extracting the starch-bound protein fractions followed by Suprose 12 gel filtration chromatography.

• Proceedings of the Korean Society of Plant Biotechnology Conference
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• 2005.11a
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• pp.351-355
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• 2005

In the storage roots of sweetpotato (Ipomoea batatas (L.) Lam. cv. Kokei 14), 10 to 20% of starch is essentially unbranched linear amylose and the other major component is branched amylopectin. Amylose is produced by the enzyme GBSSI (granule bound starch synthase I), whereas amylopectin is produced by a concerted action of soluble starch synthase and starch branching enzymes (SBEI and SBEII). We constructed double-stranded RNA (dsRNA) interference vectors of GBSSI and IbSBEII and introduced them into sweetpotato genome via Agrobacterium-mediated gene transformation. The endogenous GBSSI expression was inhibited by dsRNA of GBSSI in 73 % of transgenic plants giving rise to the storage tubers containing amylopectin but not amylose. On the other hand, all sweetpotato plants transformed with dsRNA of IbSBEII contained a larger amount of amylose than the non-transgenic control (up to 25% compared to 10% in the controls). The RNA interference (RNAi) is effectively inhibited the gene expression in thestarch metabolic pathway and modified the characteristics of starch in sweetpotato.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.229-229
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• 2017

This research study was conducted to analyze the characteristics of different rice cultivars in abnormal temperature conditions (low temperature) for ripening period abnormalities, and to investigate the physiological causes behind the abnormalities. Four Korean high quality japonica-type rice cultivars, Jinbu (JB), Junamjosaeng (JJ), Geumyoung (GY), Hwawang (HW) were used in the experiment. The following day after flowering, they were then moved into two phytotrons under natural daylight with 65% RH but controlled at different temperatures - one at $19/29^{\circ}C$ (night/day) and the other at $13/23^{\circ}C$ as the low - temperature study on ripening. For the cultivars at $13/23^{\circ}C$ (low temperature study), JB and JJ had a ripening rate of 93% which is similar to the ripening rates of cultivars at $19/29^{\circ}C$ at 45 days after heading (DAH). In contrast, GY and HW recorded lower ripening rates of 86% and 57% respectively. However, when the cultivars at $13/23^{\circ}C$ were harvested at 61 DAH (when the accumulated temperature reached $1100^{\circ}C$), the difference in ripening rates compared to the 4 cultivars of $19/29^{\circ}C$ harvested at 45 DAH was not obvious (JB 94%, JJ 97%, GY 97%, HW 88%). Starch content showed little difference among the 4 cultivars at different temperature conditions while amylose content was higher for cultivars at $13/23^{\circ}C$ compared to those at $19/29^{\circ}C$. In addition, the enzyme activities of starch biosynthesis were about 5~10 days slower in cultivars at $13/23^{\circ}C$ compared to cultivars at $19/29^{\circ}C$. The grain-filling rate showed highly significant correlations with the enzyme activities of Sucrose synthase ($R^2=0.70^{***}$), ADP glucose pyrophosphorylase ($R^2=0.63^{***}$), UDP glucose pyrophosphorylase ($R^2=0.36^{***}$), Starch synthase ($R^2=0.51^{***}$), and Starch branching enzyme ($R^2=0.59^{***}$). Among the enzymes, Sucrose synthase activity had the highest correlation coefficient with grain-filling rate. In conclusion, the activity of enzymes such as Sucrose synthase, UDP glucose pyrophosphorylase, ADP glucose pyrophosphorylase, Starch synthase, Starch branching enzyme in starch biosynthesis is proven to be highly related to the grain filling process. Notably, the decrease in the activity of Sucrose synthase and Starch branching enzyme and the late increase in ADP glucose pyrophosphorylase activity at low temperature in the ripening stage are considered to be disadvantageous as they delay ripening and increased amylose content.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.43 no.2
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• pp.89-94
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• 1998

Granule bound starch synthase (GBSS), also known as the '"waxy protein'", is responsible for the synthesis of amylose in the amyloplasts of cereal crops. In hexaploid wheat (Triticum aestivum L.), GBSS is involved in amylose synthesis and rolls as an important factor to determine flour quality and end-use quality in food products. Genes on three Wx loci have been found to encode GBSS in common wheats. We developed techniques for the purification and separation of GBSS in wheat. Three major GBSS isoforms, which were encoded by the genes on three loci, Wx-A1, Wx-B1, and Wx-D1 migrating differently by one dimensional SDS-po-lyacrylamide gel electrophoresis (1D SDS-PAGE), were identified. GBSS from 66 Korean hard and soft winter wheats were purified and determined for their Wx loci and four of them were identified possessing a null allele either at the Wx-A1 and Wx-B1 loci. With help of identification of three GBSS isoforms using 1D SDS-PAGE system, we are able to identify and monitor Wx gene expressions in breeding materials for developing waxy or partial waxy wheats without experiencing consecutive selecting generations.cting generations.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.04a
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• pp.119-119
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• 2022

• Korean Journal of Breeding Science
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• v.42 no.1
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• pp.1-10
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• 2010

Five mutants were investigated at the molecular level to determine the factors responsible for mutated endosperm types. They were classified as high (HA) or low amylose (LA) phenotypes based on the amylose content in endosperm. The five were previously produced from Ilpum and Shindongjin cultivar treated with N-methyl-N-nitrosourea and gamma-ray irradiation, respectively. Analysis of the genomic structure and expression of Granule-bounded Starch Synthase I (GBSSI) genes revealed that mutants generally showed a higher incidence of nucleotide transition than transversion, and the $A:T{\rightarrow}G:C$ transition was particularly prevalent. The rates of nucleotide substitution in HA mutants were generally higher than those in the LA mutants, leading to higher substitutions of amino acid in the HA mutants. Neither nucleotide substitutions interfering with intron splicing or causing early termination of protein translation were found, nor any large-sized deletions or additions were found in all the mutants. In principle, amylose content can be regulated by three factors: internal alterations of GBSSI protein, the strength of gene expression, and other unknown external factors. Our results indicate that the endosperm mutants from Shindongjin arose from internal alterations of GBSSI proteins, which may be the result of amino acid substitutions. On the other hand, the Ilpum mutants might be principally caused by the alteration of gene expression level. Analysis of another three glutinous cultivars revealed that the major factor leading to glutinous phenotypes is the 23-bp duplicative motif (5'-ACGGGTTCCAGGGCCTCAAGCCC-3') commonly found in exon 2, which results in the premature termination of protein translation leading to the production of a non-functional GBSSI enzyme.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.46 no.5
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• pp.360-366
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• 2001

Flour physicochemical properties of six Korean waxy wheat lines and their parental plants, including Kanto 107 and BaiHuo, which have partially null in GBSS (granule bound starch synthase), were evaluated in this study. The very low amylose content (3.20%) of Korean waxy wheat lines, which had been influenced by the null in all three GBSS isoforms encoded by three Wx loci, could result in the higher starch swelling power (25.15%), lower starch and flour pasting temperature (61.37$^{\circ}C$; 65.85$^{\circ}C$), and higher starch pasting peak viscosity and breakdown (246.60 RVU; 161.50 RVU) than those of their parental plants. In addition to high swelling and pasting properties, Korean waxy wheat lines had the higher protein content (12.80%), alkaline water retention capacity (97.39%), SDS sedimentation volume (80.33 $m\ell$) and damaged starch content (4.35 %) than those of their parental plants.

• Journal of Plant Biotechnology
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• v.36 no.3
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• pp.207-213
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• 2009

Starch serves not only as an energy source for plants, animals, and humans but also as an environmentally friendly alternative for fossil fuels. Progress in understanding of starch biosynthesis, and the isolation of many genes involved in this process have enabled the genetic modification of crops in a rational manner to produce novel starches with improved functionality. Starch is composed of two glucose polymers, amylose and amylopectin. The amylose and amylopectin ratio in starch affects its physical and physicochemical properties. Alteration in starch structure can be achieved by modifying genes encoding the enzymes responsible for starch biosynthesis and starch hydrolysis. Here, we describe recent findings concerning the starch modification in sweetpotato. Sweetpotato [Ipomoea batatas (L.) Lam] ranks seventh in annual production among food crops in the world as an important starch source. To develop transgenic sweetpotato plants with modifying starch composition, we constructed transformation vectors overexpressing granule bound starch synthase I and inhibiting amylopectin synthesis genes such as starch branching enzyme and isoamylase under the control of 35S promoter, respectively. Transformation of sweetpotato (cv. Yulmi) is in progress.

• Korean Journal of Breeding Science
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• v.42 no.5
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• pp.515-524
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• 2010

The amylose content of starch is a major factor in the texture of cooked cereal grains. Therefore, down-regulation of amylose synthesis is one of the alternative method to improve eating quality of rice. We developed transgenic rice plants designed to suppress granule-bound starch synthase I(GBSSI) gene using RNA interference(RNAi) technology. Transgenic plants with RNAi vector containing the 3'-UTR region of GBSSI showed a lower amylose content in rice endosperm than that of wild-type. The range of amylose content was 5.9~9.0% in the transgenic plants, whereas that of wild-type was 17.7~18.0%. Transgenic rices showed the decrease of short chain and the increase of long chain by analyzing chain length distribution of amylopectin in the endosperm. In the SEM micrographs, we found that compound starch granules in whole grains of the wild-type rice were readily split during fracturing, while the starch granules in RNAi-transgenic lines showed small voluminous, non-angular rounded bodies.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.218-218
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• 2022

Granules-bound starch synthase II (GBSSII), one of the isoforms of granule-bound starch synthase (GBSS), is responsible for amylose synthesis by expressing in non-storage tissues such as leaf, stem, root, and pericarp. Up to date, little is known about this gene functions and basic knowledge of heritable characteristics of this gene, GBSSII. We identified functional haplotypes and performed evolutionary analyses on the GBSSII using 374 rice accessions (320 Korean bred and 54 wild) based on the classified groups. A total of 14 haplotypes were found, and almost all haplotypes (13) were functional, carrying 19 non-synonymous SNPs in two exons (exons 1 and 2). The lowest nucleotide diversity was detected in Tropical japonica (0.00145), while the highest pi-value was in Aus (0.01081), illustrating the signal of this gene evolution. The highest Tajima's D value in Aus (1.6380) indicates GBSSII gene domestication signature under balancing selection, while the lowest Tajima's D value in Temperate japonica (-0.8243) highlights that they were under positive selection, which may be purified due to the excess of rare alleles. The highest genetic differentiation was observed between Tropical japonica and aroma (F_ST = 0.921928). In contrast, the highest interbreed level was detected in Aus-admixture (F_ST = -0.20157). The genetic relatedness between and or among the wild and cultivated subpopulations was revealed through PCA, population structure, and phylogenetic analyses.