Effectiveness of Sodium Azide Alone Compared to Sodium Azide in Combination with Methyl Nitrosurea for Rice Mutagenesis

( Thomas H. Tai ),( Areum Chun ),( Isabelle M. Henry ),( Kathie J. Ngo ),( Diana Burkart-waco ) 한국육종학회 2016 Plant Breeding and Biotechnology Vol.4 No.4

Rice seeds of the temperate japonica cultivar Kitaake were mutagenized with sodium azide alone and in combination with methyl nitrosourea. Using the reduced representation sequencing method Restriction Enzyme Sequence Comparative Analysis (RESCAN), the mutation densities, types and local sequence context were determined in the resulting M2 generation mutants. The results indicate that sodium azide is as effective alone as in combination with methyl nitrosourea in generating mutations in rice. In both cases, GC>AT transitions were the predominant mutation type and similar local sequence contexts were observed (5`-G-G-R-3` for sodium azide, 5`-R-G-R-3` for sodium azide plus methyl nitrosourea). Differences in local sequence context with those reported for another common chemical mutagen, ethyl methanesulfonate, suggests that rice mutant populations developed by combining mutants derived independently from sodium azide and ethyl methanesulfonate may exhibit a broader spectrum of mutations and mutant phenotypes.

Identifying a Candidate Mutation Underlying a Reduced Cuticle Wax Mutant of Rice Using Targeted Exon Capture and Sequencing

김현정,Thomas H. Tai 한국육종학회 2019 Plant Breeding and Biotechnology Vol.7 No.1

Aerial surfaces of terrestrial plants are protected from the uncontrolled loss of water and gas by the cuticle, a membrane of fatty acid polymers on the outer surface of epidermal cells. Composed of cutin and waxes, the cuticle protects against a wide range of external stresses and has an important role in plant development and reproduction. Plants with reduced cuticular waxes often exhibit glossy, bright green leaves, which in rice are only observed in the presence of water adhesion. In this study, a wet leaf/glossy (wlg) mutant KDS-2249D was subjected to targeted exon capture and sequencing to identify candidate mutations. A single nonsynonymous, homozygous mutation was found in the KDS-2249D mutant. The mutation (G1080A) is predicted to change a tryptophan at position 360 to a stop codon in the Glossy1-like-1/wax crystal-sparse leaf 2 gene. This mutation completely co-segregated with the wlg phenotype in an F2 mapping population (n = 435) and the KDS-2249D mutant exhibited a 40-50% decrease in total wax and significant increase in membrane permeability. This mutant will be useful for studies examining the role of cuticle waxes in protecting rice plants from environmental stresses.

Identification of QTLs Controlling Seedling Traits in Temperate Japonica Rice under Different Water Conditions

윤여태,김현정,Thomas H. Tai 한국육종학회 2019 Plant Breeding and Biotechnology Vol.7 No.2

The objective of this study was to detect QTLs for rice seedling traits under normal water (control) and low water conditions (drought stress). Ninety-eight recombinant inbred lines (RILs) from a cross between closely-related japonica cultivars, M-203 and M-206 were grown under both low water and normal water conditions. QTLs for morphological traits were investigated at seedling stage using 5,164 single nucleotide polymorphisms via genotyping-by-sequencing. Twenty-three QTLs were associated with four seedling traits: shoot length (SL), root length (RL), shoot dry weight (SW) and root dry weight (RW), were detected and most QTLs were clustered on chromosome 1, 6, 7 and 11. Under normal water conditions, nine QTLs for seedling traits were detected and M-203 alleles increased all the values. The locations of most QTLs were consistent with genes that regulate or respond to auxin and gibberellin. For drought tolerance, fourteen QTLs were detected including seven for drought stress conditions and seven for relative performance (values from drought stress conditions/normal water conditions). Seven QTLs from drought stress conditions coincided with the loci of previously identified drought tolerance genes. Based on the shoot and root length under drought stress conditions, five lines exhibiting the highest values in common were selected as a drought tolerance group. Those lines exhibited better growth than the parents under drought stress conditions and had QTLs alleles for drought tolerance detected in this study. QTL information and selected lines may be used for improving seedling vigor and drought tolerance of rice in breeding programs.

Morphological and starch characteristics of the Japonica rice mutant variety Seolgaeng for dry-milled flour

곽지은,윤미라,이점식,이정희,고상훈,Thomas H. Tai,원용재 한국식품과학회 2017 Food Science and Biotechnology Vol.26 No.1

Producing good-quality, fine rice flour is more difficult than wheat flour because the rice grain is harder. The non-glutinous Japonica-type variety Seolgaeng, derived from N-methyl-N-nitrosourea (MNU) mutagenesis, and four other varieties, representing a range of amylose contents, were evaluated in this study. Dry-milled Seolgaeng rice flour exhibited an average particle size that is <70 μm, a more uniform particle-size proportion than other varieties. Moreover, we noted significant differences in the damaged starch content in flour from Seolgaeng compared to the other varieties (p<0.05). Seolgaeng flour showed a round starch structure, which would lead to better friability, finer particle size, and less damage to the endosperm during dry milling. Indeed, among all varieties evaluated in this study, dry-milled Seolgaeng flour had the finest particle size (averaging <70 μm) and exhibited less damaged starch. With its round starch granules, Seolgaeng is a suitable candidate for drymilled rice flour.

T-DNA insertion mutants of Arabidopsis DA1 orthologous genes displayed altered plant height and yield-related traits in rice (O. sativa L.)

Shim Kyu-Chan,Luong Ngoc Ha,Tai Thomas H.,Lee Gyu-Ri,Ahn Sang-Nag,Park Inkyu 한국유전학회 2024 Genes & Genomics Vol.46 No.4

Background The Arabidopsis DA1 gene is a key player in the regulation of organ and seed development. To extend our understanding of its functional counterparts in rice, this study investigates the roles of orthologous genes, namely DA1, HDR3, HDR3.1, and the DA2 ortholog GW2, through the analysis of T-DNA insertion mutants. Objective The aim of this research is to elucidate the impact of T-DNA insertions in DA1, HDR3, HDR3.1, and GW2 on agronomic traits in rice. By evaluating homozygous plants, we specifically focus on key parameters such as plant height, tiller number, days to heading, and grain size. Methods T-DNA insertion locations were validated using PCR, and subsequent analyses were conducted on homozygous plants. Agronomic traits, including plant height, tiller number, days to heading, and grain size, were assessed. Additionally, leaf senescence assays were performed under dark incubation conditions to gauge the impact of T-DNA insertions on this physiological aspect. Results The study revealed distinctive phenotypic outcomes associated with T-DNA insertions in HDR3, HDR3.1, GW2, and DA1. Specifically, HDR3 and HDR3.1 mutants exhibited significantly reduced plant height and smaller grain size, while GW2 and DA1 mutants displayed a notable increase in both plant height and grain size compared to the wild type variety Dongjin. Leaf senescence assays further indicated delayed leaf senescence in hdr3.1 mutants, contrasting with slightly earlier leaf senescence observed in hdr3 mutants under dark incubation. Conclusions The findings underscore the pivotal roles of DA1 orthologous genes in rice, shedding light on their significance in regulating plant growth and development. The observed phenotypic variations highlight the potential of these genes as targets for crop improvement strategies, offering insights that could contribute to the enhancement of agronomic traits in rice and potentially other crops. Background The Arabidopsis DA1 gene is a key player in the regulation of organ and seed development. To extend our understanding of its functional counterparts in rice, this study investigates the roles of orthologous genes, namely DA1, HDR3, HDR3.1, and the DA2 ortholog GW2, through the analysis of T-DNA insertion mutants. Objective The aim of this research is to elucidate the impact of T-DNA insertions in DA1, HDR3, HDR3.1, and GW2 on agronomic traits in rice. By evaluating homozygous plants, we specifically focus on key parameters such as plant height, tiller number, days to heading, and grain size. Methods T-DNA insertion locations were validated using PCR, and subsequent analyses were conducted on homozygous plants. Agronomic traits, including plant height, tiller number, days to heading, and grain size, were assessed. Additionally, leaf senescence assays were performed under dark incubation conditions to gauge the impact of T-DNA insertions on this physiological aspect. Results The study revealed distinctive phenotypic outcomes associated with T-DNA insertions in HDR3, HDR3.1, GW2, and DA1. Specifically, HDR3 and HDR3.1 mutants exhibited significantly reduced plant height and smaller grain size, while GW2 and DA1 mutants displayed a notable increase in both plant height and grain size compared to the wild type variety Dongjin. Leaf senescence assays further indicated delayed leaf senescence in hdr3.1 mutants, contrasting with slightly earlier leaf senescence observed in hdr3 mutants under dark incubation. Conclusions The findings underscore the pivotal roles of DA1 orthologous genes in rice, shedding light on their significance in regulating plant growth and development. The observed phenotypic variations highlight the potential of these genes as targets for crop improvement strategies, offering insights that could contribute to the enhancement of agronomic traits in rice and potentially other crops.

Identification of Rice Mutants with Altered Grain Alkali Digestion Trait

김현정,Ralph Vin B. Imatong,Thomas H. Tai 한국육종학회 2020 Plant Breeding and Biotechnology Vol.8 No.1

Gelatinization temperature (GT) is an important component of eating and cooking quality (ECQ) of rice. While direct measurement of GT is cumbersome, the alkali spreading value (ASV) test is a robust method commonly used to rapidly identify different GT types. In this study, we employed a modified ASV assay to screen a population of chemically-induced rice (cv. Kitaake) mutants (n = 405). Two mutant families, KDS-1623B and KDS-1824B, with significantly lower ASV (higher GT type) than wild type Kitaake (low GT type) were isolated. A nonsynonymous homozygous mutation in the isoamylase-type starch debranching enzyme gene ISA1 was identified in KDS-1623B. The mutation (G2709T) is predicted to change a valine at position 354 to a leucine in the a-amylase catalytic domain of ISA1. This result is consistent with the shrunken endosperm exhibited by KDS-1623B grains and the replacement of starch with phytoglycogen in isa1 (sugary-1) mutants. The altered ASV trait in KDS-1824B appears to be controlled by a single recessive mutation; however, the causal genetic lesion remains to be determined. These mutants will be useful resources for elucidating the complex nature of starch metabolism and its influence on ECQ of rice.

Identification of Seedling Vigor-Associated Quantitative Trait Loci in Temperate Japonica Rice

( Karla I. Cordero-lara ),( Hyunjung Kim ),( Thomas H. Tai ) 한국육종학회 2016 Plant Breeding and Biotechnology Vol.4 No.4

A quantitative trait loci (QTL) analysis of seedling vigor traits was conducted under dry-seeded conditions using 176 recombinant inbred lines developed from a cross of two California temperate japonica rice varieties M-203 and M-206. Height at early seedling (HES) and height at late seedling (HLS) stage, growth rate (GR), and fresh weight were evaluated in a growth chamber. Assessment of HES, HLS, and GR was also performed in outdoor basins in 2015 and 2016. M-203 was significantly better for all traits in the growth chamber, however, no significant differences were observed between the parents in the outdoor basins with the exception of HES in 2015. Genotyping by sequencing was used to construct a map of >6,000 single nucleotide polymorphisms. Six QTL were detected in the growth chamber, one each on chromosomes 2, 9, 10, and 12 and two at the same position on 1. qFW1 and qHES1 explain 34.6% and 8.7% of the phenotypic variation observed for their respective traits and correspond to previously reported QTL for shoot length. All positive effects were contributed by the M-203 allele except for the qHLS12. Two QTL, qHES8 (12.3%; M-206 allele) and qHES9 (9.4%; M-203 allele), were detected in the outdoor basin 2016, but none in 2015. RIL-187 was consistently among the highest vigor lines in all environments and additional evaluations confirmed this finding. The molecular and genetic resources developed here will facilitate further investigation of seedling vigor and breeding of enhanced temperate japonica rice varieties.

보-기둥 접합부에서 강섬유보강 콘크리트의 효율성에 관한 연구

곽윤근(Kwak Yoon-Keun),최현태(Choi Hyun-Tai),권우현(Kwon Woo-Hyun),김우석(Kim Woo-Suk),강현구(Kang Thomas H.-K) 대한건축학회 2010 大韓建築學會論文集 : 構造系 Vol.26 No.9

For the sufficient strength and ductile behavior of RC beam-column joints, closely-spaced lateral confinement reinforcement is required by seismic design codes. However, such seismic design often hinders the economic efficiency and constructability of a structure. The use of steel fibers in RC beam-column joints can improve the cost effectiveness and overcome fabrication complications, such as congested reinforcement details and associated poor concrete placement, without altering its seismic performance. To investigate the effect of steel fibers in RC beam-column joints, an experimental study was carried out under seismic loading conditions. A total of six half-scale joint specimens with seismic details or replacing steel fibers were subjected to three reversed cycles at each drift level up to 6% lateral drift ratio. The variables studied in this investigation are the joint transverse reinforcement amount and steel fiber volume fraction (0, 1, and 1.5%). The results of tests show that lateral load capacity, energy dissipation capacity, shear strength and ductility, and drift capacity are improved with the application of steel fibers of 1.5% but with the same configuration for the rest of the details. Also, a detailed analysis of both global and local data reveals the possibility of substituting steel fibers for some of the transverse reinforcement.

The phytochelatin transporters AtABCC1 and AtABCC2 mediate tolerance to cadmium and mercury

Park, Jiyoung,Song, Won‐,Yong,Ko, Donghwi,Eom, Yujin,Hansen, Thomas H.,Schiller, Michaela,Lee, Tai Gyu,Martinoia, Enrico,Lee, Youngsook Blackwell Publishing Ltd 2012 The Plant journal Vol.69 No.2

<P><B>Summary</B></P><P>Heavy metals such as cadmium (Cd) and mercury (Hg) are toxic pollutants that are detrimental to living organisms. Plants employ a two‐step mechanism to detoxify toxic ions. First, phytochelatins bind to the toxic ion, and then the metal–phytochelatin complex is sequestered in the vacuole. Two ABCC‐type transporters, AtABCC1 and AtABCC2, that play a key role in arsenic detoxification, have recently been identified in <I>Arabidopsis thaliana</I>. However, it is unclear whether these transporters are also implicated in phytochelatin‐dependent detoxification of other heavy metals such as Cd(II) and Hg(II). Here, we show that <I>atabcc1</I> single or <I>atabcc1 atabcc2</I> double knockout mutants exhibit a hypersensitive phenotype in the presence of Cd(II) and Hg(II). Microscopic analysis using a Cd‐sensitive probe revealed that Cd is mostly located in the cytosol of protoplasts of the double mutant, whereas it occurs mainly in the vacuole of wild‐type cells. This suggests that the two ABCC transporters are important for vacuolar sequestration of Cd. Heterologous expression of the transporters in <I>Saccharomyces cerevisiae</I> confirmed their role in heavy metal tolerance. Over‐expression of <I>AtABCC1</I> in Arabidopsis resulted in enhanced Cd(II) tolerance and accumulation. Together, these results demonstrate that AtABCC1 and AtABCC2 are important vacuolar transporters that confer tolerance to cadmium and mercury, in addition to their role in arsenic detoxification. These transporters provide useful tools for genetic engineering of plants with enhanced metal tolerance and accumulation, which are desirable characteristics for phytoremediation.</P>

Characterization of Genes Associated with Salt Tolerance Using Transcriptome Analysis and Quantitative Trait Loci Mapping in Rice

( Dong-min Kim ),( Ju-won Kang ),( Kyu-chan Shim ),( Hyun-jung Kim ),( Thomas H. Tai ),( Sang-nag Ahn ) 한국육종학회 2021 Plant Breeding and Biotechnology Vol.9 No.4

We conducted transcriptome profiling analysis of O. glaberrima root using RNA-Seq at the control (OCR) and 100 mM NaCl treatment (OTR) at two time points (6 and 24 hours after treatment) to detect genes induced by salt stress. RNA-Seq analysis generated 102,690,698 sequence reads representing 30,388 predicted transcripts including 6,189 unannotated in Rice Annotation Project database. A total of 539 and 424 of differentially expressed genes (DEGs) were detected between OCR_6hours vs OTR_6hours and between OCR_24hours vs OTR_24hours, respectively (P < 0.001, q < 0.05). Among these DEGs, 262 genes showed constant differential expression at both 6 hours and 24 hours, and these included a bHLH containing protein, WRKY transcription factor, serine/threonine kinase, R2R3 MYB protein, and amino acid transporters. Interestingly, an enhanced seedling salt tolerant introgression line IL55 from a cross between a salt sensitive indica cultivar “Milyang23” and O. glaberrima harbors one DEG, Os02g0787300 encoding a mitogen activated protein kinase kinase (MAPKK) on chromosome 2. Analysis of the salt tolerance of the F_2:3 lines from a cross between IL55 and Milyang23 indicated that the O. glaberrima segment on chromosome 2 containing the MAPKK gene was responsible for better shoot growth under salt stress at the seedling stage. The salt inducible genes will be evaluated in introgression lines (ILs) to understand whether the expression of these genes is associated with salt tolerance in ILs having the Milyang23 genetic background. Transcriptome sequence information in this study may be useful for developing DNA markers linked to salinity tolerance for MAS breeding.