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631.
Genetic diversity in two species of Impatiens in Korea was investigated using starch gel electrophoresis. Impatiens hypophylla is a rare species endemic to southwestern Japan and southeastern Korea, whereas I. rextori is widespread in East Asia. Impatiens textori has considerably higher genetic diversity than I. hypophylla . For example, mean values of genetic diversity within populations (He) of I. textori and I. hypophylla were 0.206 and 0.102, respectively. The high outcrossing rate (mean 1 = 0.89), abundance and widespread distribution, and large population size may be factors responsible for the maintenance of high levels of genetic variation in I. textori . Analyss of fixation indices indicated that considerable population substructuring within populations of I. hypophylla , partly resulting from inbreeding and/or genetic drift in small populations coupled with limited gene flow (mean FIS = 0.699). However, the degree of population divergence observed in I. hypophylla (mean GST = 0.059) was considerably lower than that in other plants with similar life history traits. It is supposed that similar selection at populations of I. hypophylla examined might maintain similar gene frequencies in isolated populations. 相似文献
632.
Abstract The hostas native to Korea have never been carefully reviewed taxonomically and their patterns of variability are not well understood. For morphological and electrophoretic studies, samples of rootstocks were taken from 45 Korean Hosta populations and from two populations of H. tsushimensis N. Fujita on Tsushima Island, Japan. For morphometric analysis, ten plants from each of twenty populations were grown and observed under greenhouse conditions. Fifty-one floral and vegetative characters were examined on each plant and the data were analyzed using principal components and cluster analysis. Six Korean species can be recognized: H. yingeri S. B. Jones (Taehuksan, Sohuksan, and Hong islands); H. capitata (Koidz.) Nakai (southern Korea); H. clausa Nakai (central and northern Korea); H. minor (Baker) Nakai (southeastern Korea including Wan and Kojae islands); H. venusta F. Maekawa (Cheju Island); and H. jonesii M. Chung (southern islands). Morphological features contributing to recognition of the natural groups were: ridges on the scape; the width of inner and outer floral lobes; bracts pappillous at apex; length and color of the bracts; length of inflorescences; the withering condition of the bracts; scabrous nerves on the lower leaf surface; and size of the leaves. Isozyme analyses indicate a recent origin of H. venusta from H. minor. Although hostas are easily hybridized, natural hybridization seems to be rare in Korea. The morphological and isozyme studies identified no hybrids and the species are well characterized by their distribution patterns, phenology, and habitats. 相似文献
633.
634.
Myong Gi Chung 《Journal of plant research》1994,107(4):377-383
Hosta minor, an insect-pollinated and rhizomatous herbaceous perennial, occurs in eastern and southern Korean Peninsula. AlthoughH. minor is a Korean endemic species and most populations of the species are scattered, the species maintains considerably high levels
of genetic variation within the species, with a moderate level of variation (14%) found among populations. Nineteen of the
29 putative loci resolved (66%) were polymorphic within the species, the mean number of alleles per locus was 2.10 across
all populations and averaged 1.68 within populations. In addition, genetic diversity was a considerably higher (for species
and population level, mean estimates of genetic diversity were 0.275 and 0.230, respectively) than the average for other long-lived
herbaceous perennials. Indirect estimate of the number of migrants per generation (Nm=1.03, calculated from mean GST) was moderate. Factors contributing to the high levels of genetic diversity found within populations ofH. minor include population maintenance via sexual and asexual modes of reproduction, primarily outcrossing breeding system, long
generation time, probable ancient polyploid origin of the species, and moderate levels of seed dispersal by wind. Human disturbance
in South Korea such as road and apartment constructions appears to be the major threat to this genetically diverse species. 相似文献
635.
Salsola komarovi lljin is a herbaceous annual native to the sand dunes and beaches of Japan, northern China, Sakhalln and Korea. Starch-gel
electrophoresis was conducted on leaves and stems collected from 300 plants in eight Korean populations. The mean number of
alleles per locus (A
p=1.51), mean expected heterozygosity (He
p=0.116), and total genetic diversity (H
T=0.279) were comparable with those for species with similar life history and ecological traits. A general conformance of genotype
frequencies to Hardy-Weinberg expectations (meanF
IS=−0.030) indicates thatS. komarovi is an outcrossing species. Slightly more than 20% of the genetic variation was found among populations (F
ST=0.204). In addition, significant differences in allele frequency were detected between populations at all 11 polymorphic
loci (P<0.001). Nei's genetic identities range from 0.885 to 0.985 with a mean of 0.942. However, indirect estimates of the number
of migrant per generation (0.97, calculated fromF
ST and 0.31, calculated from seven private alleles) indicate that the levels of gene flow is low among Korean populations. Although
the species maintains a moderate level of genetic variation within populations, the small, isolated natural populations of
the species have been severely destructed by human activities, particularly in summer season. If this is true, conservation
efforts should be focused on those populations that currently maintain the most genetic diversity (e.g., populations of Cheju
Island and coast of the southwestern Korean Peninsula). 相似文献
636.
Jae Sung Park Gi Hwan Yi Min Hee Nam Sun Ho Park 《Biotechnology and Bioprocess Engineering》2001,6(1):51-55
This study was conducted to establish a plant cell culture system for the production of medically important secondary metabolites
fromXanthium strumarium. The effects of plant growth regulators including NAA, 2,4-D, kinetin, and ABA were examined in terms of callus induction,
maintenance of callus and suspension cultures. It was shown that callus was induced upon treatment with NAA while embryo was
induced after treatment with 2,4-D. Callus formation was further improved by treatment with ABA and NAA. The level of callusing
increased by 17–29% for the seed case, cotyledon, leaf, and hypocotyl and by 96% in the case of the root. Suspension cell
lines were established using calli produced from cotyledon, hypocotyl and root and cultured at 25°C under light conditions.
The cells grew up to 15 g/L with NAA 2 ppm, BA 2 ppm, and ABA 1 ppm treatment. Supernatants of suspension cultures of cell
lines derived from coyledon and hypocotyl produced some distinctive secondary metabolites, one of which was identified as
8-epi-tomentosin, which belongs to the xanthanolides. The amounts of 8-epi-tomentosin produced by the cotyledon-and hypocotylderived cell lines were 13.4 mg/L and 11.0 mg/L, respectively. 相似文献
637.
Kwon NR Chae JC Choi KY Yoo M Zylstra GJ Kim YM Kang BS Kim E 《Applied microbiology and biotechnology》2008,79(3):417-422
A novel indigo-producing oxygenase gene, designated ipoA (1,197 bp) was characterized from Rhodococcus sp. strain T104. Three indigo-negative mutations (A58V, P59L, and G251D) were obtained through random mutagenesis using an E. coli mutator strain. Subsequent saturation mutagenesis resulted in the identification of nine and three amino acid substitutions that restore activity in the A58V and P59L mutants, respectively. Activity was not restored in the G251D mutation by any other amino acids. Interestingly, activity in the A58V mutant, where a methyl group is only replaced by an isopropyl side chain, is restored by a variety of amino acids, including polar ones. A molecular modeling study suggests that the residues at positions 58, 59, and 251 of the T104 IpoA enzyme are far from the active site, indicating that the mutations must alter the overall structure of the enzyme. 相似文献
638.
Gião MS Azevedo NF Wilks SA Vieira MJ Keevil CW 《Applied and environmental microbiology》2008,74(19):5898-5904
Although the route of transmission of Helicobacter pylori remains unknown, drinking water has been considered a possible transmission vector. It has been shown previously that, in water, biofilms are a protective niche for several pathogens, protecting them from stressful conditions, such as low carbon concentration, shear stress, and less-than-optimal temperatures. In this work, the influence of these three parameters on the persistence and cultivability of H. pylori in drinking-water biofilms was studied. Autochthonous biofilm consortia were formed in a two-stage chemostat system and then inoculated with the pathogen. Total numbers of H. pylori cells were determined by microscopy using a specific H. pylori 16S rRNA peptide nucleic acid probe, whereas cultivable cells were assessed by standard plating onto selective H. pylori medium. Cultivable H. pylori could not be detected at any time point, but the ability of H. pylori cells to incorporate, undergo morphological transformations, persist, and even agglomerate in biofilms for at least 31 days without a noticeable decrease in the total cell number (on average, the concentration was between 1.54 x 10(6) and 2.25 x 10(6) cells cm(-2)) or in the intracellular rRNA content may indicate that the loss of cultivability was due to entry into a viable but noncultivable state. Unlike previous results obtained for pure-culture H. pylori biofilms, shear stress did not negatively influence the numbers of H. pylori cells attached, suggesting that the autochthonous aquatic bacteria have an important role in retaining this pathogen in the sessile state, possibly by providing suitable microaerophilic environments or linking biomolecules to which the pathogen adheres. Therefore, biofilms appear to provide not only a safe haven for H. pylori but also a concentration mechanism so that subsequent sloughing releases a concentrated bolus of cells that might be infectious and that could escape routine grab sample microbiological analyses and be a cause of concern for public health. 相似文献
639.
Rohini Dwivedi Priyanka Samanta Poonam Sharma Fuming Zhang Sushil K. Mishra Pavel Kucheryavy Seon Beom Kim AyoOluwa O. Aderibigbe Robert J. Linhardt Ritesh Tandon Robert J. Doerksen Vitor H. Pomin 《The Journal of biological chemistry》2021,297(4)
Certain sulfated glycans, including those from marine sources, can show potential effects against SARS-CoV-2. Here, a new fucosylated chondroitin sulfate (FucCS) from the sea cucumber Pentacta pygmaea (PpFucCS) (MW ∼10–60 kDa) was isolated and structurally characterized by NMR. PpFucCS is composed of {→3)-β-GalNAcX-(1→4)-β-GlcA-[(3→1)Y]-(1→}, where X = 4S (80%), 6S (10%) or nonsulfated (10%), Y = α-Fuc2,4S (40%), α-Fuc2,4S-(1→4)-α-Fuc (30%), or α-Fuc4S (30%), and S = SO3−. The anti-SARS-CoV-2 activity of PpFucCS and those of the FucCS and sulfated fucan isolated from Isostichopus badionotus (IbFucCS and IbSF) were compared with that of heparin. IC50 values demonstrated the activity of the three holothurian sulfated glycans to be ∼12 times more efficient than heparin, with no cytotoxic effects. The dissociation constant (KD) values obtained by surface plasmon resonance of the wildtype SARS-CoV-2 spike (S)-protein receptor-binding domain (RBD) and N501Y mutant RBD in interactions with the heparin-immobilized sensor chip were 94 and 1.8 × 103 nM, respectively. Competitive surface plasmon resonance inhibition analysis of PpFucCS, IbFucCS, and IbSF against heparin binding to wildtype S-protein showed IC50 values (in the nanomolar range) 6, 25, and 6 times more efficient than heparin, respectively. Data from computational simulations suggest an influence of the sulfation patterns of the Fuc units on hydrogen bonding with GlcA and that conformational change of some of the oligosaccharide structures occurs upon S-protein RBD binding. Compared with heparin, negligible anticoagulant action was observed for IbSF. Our results suggest that IbSF may represent a promising molecule for future investigations against SARS-CoV-2. 相似文献
640.
Hye Jin Shin Keun Bon Ku Hae Soo Kim Hyun Woo Moon Gi Uk Jeong Insu Hwang Gun Young Yoon Sunhee Lee Sumin Lee Dae-Gyun Ahn Kyun-Do Kim Young-Chan Kwon Bum-Tae Kim Seong-Jun Kim Chonsaeng Kim 《International journal of biological sciences》2021,17(14):3786
COVID-19, caused by a novel coronavirus, SARS-CoV-2, poses a serious global threat. It was first reported in 2019 in China and has now dramatically spread across the world. It is crucial to develop therapeutics to mitigate severe disease and viral spread. The receptor-binding domains (RBDs) in the spike protein of SARS-CoV and MERS-CoV have shown anti-viral activity in previous reports suggesting that this domain has high potential for development as therapeutics. To evaluate the potential antiviral activity of recombinant SARS-CoV-2 RBD proteins, we determined the RBD residues of SARS-CoV-2 using a homology search with RBD of SARS-CoV. For efficient expression and purification, the signal peptide of spike protein was identified and used to generate constructs expressing recombinant RBD proteins. Highly purified RBD protein fused with the Fc domain of human IgG showed potent anti-viral efficacy, which was better than that of a protein fused with a histidine tag. Intranasally pre-administrated RBD protein also inhibited the attachment of SARS-COV-2 to mouse lungs. These findings indicate that RBD protein could be used for the prevention and treatment of SARS-CoV-2 infection. 相似文献