광발아성을 갖는 잡초성 벼의 발견

백남천 서울대학교 농업개발연구소 1999 농업생명과학연구 Vol.3 No.-

Photoregulation of seed germination is the important character of plant species producing small seeds such as lettuce, tobacco, Arabidopsis, and Gramineae weeds, etc. It has been known that there is no photoblastism in rice seeds. Here we present at first that a photoblastic rice (PBR) seed was discovered among Korean weedy rice lines. The PBR seed identified among the 235 weedy rice lines germinated about 99% under white light and 0.3% in total darkness. When the PBR seeds were planted, it showed the variation of emergency rate according to the burial depth and temperature. In the 18/12℃ (day/night) diurnal condition, the emergency rate was 39% at 1 cm burial depth, 15% at 3~5cm, 5% at 7cm, and 1% at 10 cm. The deeper the seeds were planted, the lower the emergency showed. Under 24/22℃ condition, the emergency rate at 1 cm burial depth was only 6%. When the PBR seeds were stored at room temperature after harvest, seed dormancy and photoblastism were gradually decayed. The seed dormancy disappeared more than 90% after 3-month storage. Photoblastism disappeared 26% after 16 months and 63% after 28 months. The seed dormancy of the PBR was broken by high temperature(50℃ for 7days) to dry seeds and, however, the photoblastism was not influenced and still maintained. In the amount of light and imbibition time, the more the seeds were irradiated, the higher germination rate was. The more imbibition time before light was, the more germination was delayed. In the response of light quality, the germination rate of the PBR seeds was promoted by red light and inhibited by far-red light, indicating that the seed germination was controlled by phytochromes. It also showed photoreversibility. The seed germination of PBR was alternately promoted or inhibited by the final irradiation of red or far-red light.

Barley yellow dwarf virus의 분자학적 동정 및 밀에서의 저항성 유전자원 탐색

백남천 서울대학교 농업개발연구소 2000 농업생명과학연구 Vol.4 No.-

Barley Yellow Dwarf Virus (BYDV), an aphid-borne luteovirus, is a major plant pathogenic disease causing a huge economic loss in the grain production of a wide range of Gramineae species throughout the world. It has been recently reported that BYDV also occurred frequently in wheat field in Korea. We performed to develop the detection and classification methods of BYDV strains that were accomplished by reverse transcription-polymerase chain reaction (RT-PCR), to investigate the regional distributions of BYDV strains in Korea, and to identify the resistant cultivars or lines of wheat to the predominant BYDV strains, providing basic information for the breeding of BYDV-resistant wheat varieties. Since there are high variations among BYDV strains, three pairs of primers were designed to detect BYDV strains such as PAV(Vic-PAV and CN-PAV) and MAV (primer A) simultaneously, specifically Vic-PAV (primer B), and MAV (primer C) based on the genomic RNA sequences of BYDV strains reported previously. The validity of the primers was confirmed using several BYDV strains obtained from CIMMYT. Though three BYDV strains were able to be detected using primer A, PCR products were not distinguished between two PAV strains. It was possible to separate them with a restriction enzyme, EcoRI, whose restriction site was present in the amplified DNA fragment from Vic-PAV, but not from CN-PAV. Using these methods, the regional distribution of BYDV strains in Korea from 1999 to 2000 showed that PAV strain was mainly detected about 65% (Vic-PAV 52.6%; CN-PAV 47.4%) and MAV strain about 3%. Using ELISA test for the examination of BYDV resistance with 17 cultivars and 4 lines among Korean wheat, three cultivars, Gurumil, Topdongmil, and Olgurumil, were susceptible to BYDV and the others were resistant. In plant growth and yield component responses to BYDV infection, Gurumil showed significant difference between the uninfected and the infected, suggesting the most susceptible to BYDV among Korean wheat, but Eunpamil and Seohae118 did no difference, an indication that they have the highest resistance.

The Arabidopsis Transcription Factor NAC016 Promotes Drought Stress Responses by Repressing <i>AREB1</i> Transcription through a Trifurcate Feed-Forward Regulatory Loop Involving NAP

Sakuraba, Yasuhito,Kim, Ye-Sol,Han, Su-Hyun,Lee, Byoung-Doo,Paek, Nam-Chon American Society of Plant Biologists 2015 The Plant cell Vol.27 No.6

<P>The Arabidopsis transcription factor NAC016 activates drought stress responses by inducing <I>NAP</I> transcription and repressing <I>AREB1</I> transcription by binding to different regions of the <I>AREB1</I> promoter.</P><P>Drought and other abiotic stresses negatively affect plant growth and development and thus reduce productivity. The plant-specific NAM/ATAF1/2/CUC2 (NAC) transcription factors have important roles in abiotic stress-responsive signaling. Here, we show that <I>Arabidopsis thaliana</I> NAC016 is involved in drought stress responses; <I>nac016</I> mutants have high drought tolerance, and <I>NAC016</I>-overexpressing (<I>NAC016</I>-OX) plants have low drought tolerance. Using genome-wide gene expression microarray analysis and MEME motif searches, we identified the NAC016-specific binding motif (NAC16BM), GATTGGAT[AT]CA, in the promoters of genes downregulated in <I>nac016-1</I> mutants. The NAC16BM sequence does not contain the core NAC binding motif CACG (or its reverse complement CGTG). NAC016 directly binds to the NAC16BM in the promoter of <I>ABSCISIC ACID-RESPONSIVE ELEMENT BINDING PROTEIN1</I> (<I>AREB1</I>), which encodes a central transcription factor in the stress-responsive abscisic acid signaling pathway and represses <I>AREB1</I> transcription. We found that knockout mutants of the NAC016 target gene <I>NAC-LIKE, ACTIVATED BY AP3/PI</I> (<I>NAP</I>) also exhibited strong drought tolerance; moreover, NAP binds to the <I>AREB1</I> promoter and suppresses <I>AREB1</I> transcription. Taking these results together, we propose that a trifurcate feed-forward pathway involving <I>NAC016</I>, <I>NAP</I>, and <I>AREB1</I> functions in the drought stress response, in addition to affecting leaf senescence in Arabidopsis.</P>

大麥의 半矮性 短稈 및 GA反應性의 遺傳 Ⅰ. 半矮性 短桿形質의 遺傳分析

Nam Chon Paek(白南天),Moo Hee Yang(楊武熙),Jai Wook Shim(沈載昱) 한국육종학회 1987 한국육종학회지 Vol.19 No.3

This investigation was carried out to identify dwarfing sources of five Korean barley cultivars, Baekdong, Namhae, Songhak, Paldal, and Dusan 8. Three foreign cultivars, Himalaya, Svanhals, and Baitori 10 were used as the genetic markers of the dwarf genes, br, br₂ and uz respectively. Eight cultivars were crossed by all possible combinations so as to know the genetic sources of their culm lengths. The major dwarf gene of Baekdong was the uz by which Baitori 10 was controlled. Songhak was controlled by two independent recessive dwarf genes and one of them was considered to be uz gene. The crosses between Korean cultivars, Namhae, Paldal and Dusan 8, and the cultivars of three genetic markers showed that three Korean cultivars were controlled by one recessive dwarf gene different from br,br₂ and uz gene. In the crosses among three Korean cultivars, Namhae, Paldal, Dusan 8, each one was controlled by different gene or genes from another ones.

Chlorophyll degradation through interactions of Stay-green and chlorophyll catabolic enzymes at thylakoid membrane during leaf senescence

Nam-Chon Paek 한국육종학회 2012 한국육종학회 심포지엄 Vol.2012 No.07

Loss of leaf green color results from chlorophyll (Chl) degradation in the chloroplasts, but little is known about how Chl catabolism is tightly regulated throughout development. Using the stay-green (sgr) mutant in rice which maintains leaf greenness during senescence, we identified SGR by map-based cloning. SGR is a function-unknown gene encoding senescence-induced chloroplast protein. Transgenic rice overexpressing SGR produced yellow leaves, indicating that SGR regulates Chl degradation at the transcriptional level. Leaf stay-greenness of the sgr mutant is mainly associated with a failure in the destabilization of light-harvesting complexes (LHCs) of thylakoid membranes, which is a prerequisite event for the degradation of Chl and LHCs during leaf senescence. SGR binds to light harvesting complex of photosystem II (LHCII), but its biochemical role is so far unknown. During senescence, Chl should be degraded rapidly and safely because Chl catabolic intermediates producing ROS under light are extremely toxic to the plant cells. For safe and rapid degradation of Chl and its catabolic intermediates, Chl catabolic enzymes (CCEs) must catch the Chl intermediates effectively. In recent years, although molecular functions of SGR and CCEs have been characterized in detail, their biochemical mechanism for Chl detoxification remain elusive. Here we show that all five CCEs also specifically interact with LHCII. In addition, SGR and CCEs interact directly or indirectly with each other at LHCII, and SGR is essential for recruiting CCEs in senescing chloroplasts. These data indicate a predominant role for the SGR-CCE-LHCII protein interaction in the breakdown of LHCII-located Chl, likely to allow metabolic channeling of phototoxic Chl breakdown intermediates upstream of nontoxic pFCC.

Interrelation between N and S Nutrition on Accumulation of Storage Protein in Soybean Seed

Nam Chon Paek,Richard Shibles 한국자원식물학회 1998 Plant Resources Vol.1 No.2

Soybean is an important crop because its seed has very high protein relative to others. The quality of soy protein is limited by the concentration of the sulfur-containing amino acids in the amino acid profile. Among the supply of various forms of 0.4mM sulfur as S nutrition during seed fill, only 0.4mM L-methionine can inhibit B-subunit synthesis completely and produce the highest glycinin-containing seeds. Compared to 0.4mM sulfate control, seeds supplied by 0.4mM L-methionine have lower a-, no B-subunit, and highly increased glycinin without altering total protein concentration. Supply of 0.2mM cystine (0.4mM S) did not affect the accumulative pattern of seed storage protein (SSP) subunits. In the supply of L-methionine, 0.2mM treatment showed higher glycinin in seeds but 0.05mm resulted in lower glycinin than the sulfate control. The relative abundance of a -subunit was not altered by any N or S nutrition. Under 5mM nitrogen, protein concentration was increased about 3-5% by substituting ammonia for nitrate during seed fill independent of S nutrition. This increase resulted in the only increase of 7S protein, mainly B-subunit. Our data suggest that the regulatory system of SSP genes responds to the balance between N and S assimilates supplied from mother plant, and controls the differential synthesis of their subunits for the maximum protein accumulation in developing soybean seed.

Cloning, Characterization, and Functional Analysis of Maize DEHYDRIN2

Paek, Nam-Chon,Jung, Hun-Ki The Korean Society of Crop Science 2002 한국작물학회지 Vol.47 No.2

Dehydrins (LEA Dll proteins) are one of the typical families of plant proteins that accumulate in response to dehydration, cold stress, abscisic acid, or during seed maturation. A 1.3-kb cDNA was cloned from a cDNA expression library of 5-day-old germinating maize scutellums under drought stress. The deduced protein sequence indicated a dehydrin gene encoding SK$_3$ LEA protein typically expressed during cold acclimation, but not by drought stress in barley and wheat. Thus, it was named maize DEHYDRIN2 (ZmDhn2). It accumulates rapidly and highly in drought-stressed scutellum and leaf tissues at any stage, but not under cold stress. ZmDhn2 gene was transformed into Arabidopsis thaliana for functional analysis under drought condition. From electrolyte leakage test, no significant difference showed between wild type and transformants under normal growth condition, but the leakage level of electrolyte in wild type plants was about 3 times as high as that in the transformed plants under drought stress. It suggests that ZmDHN2 playa role in increasing drought tolerance.

Detection and Classification of Barley Yellow Dwarf Virus Strains Using RT-PCR

Paek, Nam-Chon,Woo, Mi-Ok,Kim, Yul-Ho,Kim, Ok-Sun,Nam, Jung-Hyun The Korean Society of Crop Science 2001 Korean journal of crop science Vol.46 No.1

Barley Yellow Dwarf Virus (BYDV), an aphid-borne luteovirus, is a major plant pathogenic disease causing a huge economic loss in the grain production of a wide range of Gramineae species throughout the world. It has been recently reported that BYDV also occurred frequently in wheat field of Korea. Here, we performed to develop the detection and classification methods of BYDV strains that were accomplished by reverse transcription-polymerase chain reaction (RT-PCR). Since there are high variations among BYDV strains, three pairs of primers were designed to detect BYDV strains such as PAV (Vic-PAV and CN-PAV) and MAV (primer A) simultaneously, specifically Vic-PAV(primer B), and MAV (primer C) based on the genomic RNA sequences of BYDV strains previously published. The validity of the primers was confirmed using several BYDV strains obtained from CIMMYT. Though three BYDV strains were able to be detected using primer A, PCR products were not distinguished between two PAV strains. It was possible to separate them with a restriction enzyme, EcoRI, whose restriction site was present in the amplified DNA fragment from Vic-PAV, but not from CN-PAV.

Isolation, characterization, and genetic mapping of stay-green mutant in rice

Paek, Nam-Chon 서울대학교 농업개발연구소 2001 농업생명과학연구 Vol.5 No.-

Leaf color turns yellow during senescence due to the degradation of chlorophylls and photosynthetic proteins. A stay-green mutant was isolated from the glutinous japonica rice Hwacheong-wx through N-methyl-N-nitrosourea mutagenesis. Leaves of the mutant remained green while turning yellow in those of the wild-type rice during senescence. The stay-green phenotype was controlled by a single recessive nuclear gene, tentatively symbolized as sgr(t). All the phenotypic characteristics of the mutant were the same as those of the wild-type lines except for the stay-green trait. Leaf chlorophyll concentration of the mutant was similar to that of the wild type before heading, but decreased steeply in the wild type during grain filling, while very slowly in the mutant. However, no difference in photosynthetic activity was observed between the stay-green mutant and the yellowing wild-type leaves, indicating that senescence is proceeding normally in the mutant leaves and the mutation affects the rate of chlorophyll degradation during the leaf senescence. Using phenotypic and molecular markers, we mapped the sgr(t) locus to the long arm of chromosome 9 between RFLP markers RG662 and C985 at 1.8 and 2.1 cM intervals, respectively.

Effects of Sulfur Nutritional Forms on Accumulation of Seed Storage Proteins in Soybean(Glycine max)

Nam-Chon Paek 한국자원식물학회 1997 한국자원식물학회지 Vol.10 No.3

Improvement of seed protein quality might be an essential issue in soybean and would give more profit directly to both farmers and users. This study was carried out to investigate the effects of reduced-S form(s) on seed storage protein components in soybean during seed filling stages. The reduced-S forms during seed fill were sodium thiosulfate, sodium sulfite, sodium sulfide, thioacetate, β-mercaptoethanol, thiourea, thiamine-HCl, L-cysteine, L-cystine, and L-methionine. Seed storage protein concentration did not appear to be affected by any reduced-S forms. However, glycinin and β-conglycinin concentrations seemed to be changed greatly by L-methionine. This resulted in the increase in the 11S/7S ratio(3.58). Among the β-conglycinin, β-subunit was not accumulated at all. α-subunit concentration appeared to be decreased and α -subunit concentration was not altered in comparison with sulfate control. Also, β-conglycine concentration, especially β-subunit concentration, tended to be decreased with L-cystine treatment, resulting in an increase in the 11S/7S ratio(l.83). The glycinin concentration tended to be increased at the expense of the decrease in the β-conglycinin concentration. Therefore, it is suggested that enhancing soybean protein quality would be achieved by improving metabolic pathways of S assimilation in soybean plants during seed filling period under sulfate-sufficient condition.