• Journal of Microbiology and Biotechnology
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• v.12 no.2
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• pp.249-257
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• 2002

Pseudomonas fluorescens GL20 is a plant growth-promoting rhizobacterium that produces a large amount of hydroxamate siderophore under iron-limited conditions. The strain GL20 considerably inhibited the spore germination and hyphal growth of a plant pathogenic fungus, Fusarium solani, when iron was limited, significantly suppressed the root-rot disease on beans caused by F. solani, and enhanced the plant growth. The mechanism for the beneficial effect of strain GL20 on the disease suppression was due to the siderophore production, evidenced by mutant strains derived from the strain. Analysis of the outer membrane protein profile revealed that the growth of strain GL20 induced the synthesis of specific iron-regulated outer membrane proteins with molecular masses of 85- and 90 kDa as the high-affinity receptors for the ferric siderophore. In addition, a cross-feeding assay revealed the presence of multiple inducible receptors for heterologous siderophores in the strain. In order to induce increased efficacy and potential in biological control of plant disease, a siderophore-overproducing mutant, GL20-S207, was prepared by NTG mutagenesis. The mutant GL20-S207 produced nearly 2.3 times more siderophore than the parent strain. In pot trials of beans with F. solani, the mutant increased plant growth up to 1.5 times compared with that of the parent strain. These results suggest that the plant growth-promoting P. fluorescens GL20 and the genetically bred P. fluorescens GL20-S207 can play an important role in the biological control of soil-borne plant diseases in the rhizosphere.

• Journal of Microbiology and Biotechnology
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• v.11 no.6
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• pp.1061-1065
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• 2001

The antibacterial effects of water extracts of Scutellariate Radix (a dried root of Scutellaria baicalensis GEORGI) and its major flavonoid components, Baicalin and Baicalein, on Salmonella typhimurium, a representative enteric pathogen, were studied. Through a Kriby-Bauer disc analysis, the growth-inhibition activity of Scutellariae Radix against. S. typhimurium was found to be compatible with commercial antibiotics, such as ampicillin, chloramphenicol, and streptomycin. In contrast, the growth of a nonpathogenic E. coli strain was unaffercted by Scutellariae Radix. To examine the effect of polyphosphate kinase (ppk), a putative virulence factor, on the antibacterial activity of Scutellariae Radix, the growth profile of a ppk mutant of S. typhimurium was investigated in a tryptic soy broth containing different concentrations of water extracts of Scutellariae Radix. The ppk mutant was able to grow in 6 mg/ml of water extracts of Scutellariae Radix, whereas in 6 mg/ml of water extracts of Scutellariae Radix, whereas the wild-type could not, implying that the inactivation of ppk made S. typhimurium more resistant to the antibacterial activity of Scutellariae Radix. No enhanced resistance was observed in a ppk mutant of S. typhimurium complemented with a ppk expression vector. The attenuation of the virulence by ppk inactivation was also observed in a virulence assay using BLAB/c mice. Neither Baicalin nor Baicalein exhibited any growth-inhibition activity against S. typhimurium. The water extracts of Scutellariae Radix stimulated the transcription of ppk, especially in the early growth-stage of S. typhimurium.

• The Korean Journal of Mycology
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• v.22 no.4
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• pp.332-337
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• 1994

Under standard condition (Han, et al., 1990: glucose 1%-nitrate 0.1% minimal medium, 30 ml in 9 cm plate, $10^6$ cells of inoculum per plate), wild type of Aspergillus nidulans developed both sexual and asexual organs in ballance, while velA1 mutant developed asexual ones preferentially. Increase of glucose concentration did not significantly affect the asexual sporulation. However, development of sexual organs were largely affected. It was greatly enhanced when favorable nitrogen source, for example, casein hydrolysate was added, which is contrary to the case of Neurospora or Saccharomyces where limitation of N source induces sexual development. On most of moderate C sources asexual development in $velA^+$ strain was largely inhibited except acetate on which only asexual spores were produced, while that in velA1 mutant strain was not affected. Lactose promoted the sexual development even in velA1 mutant indicating that lactose itself or its metabolic intermediate may induce sexual development independent of allelic state of velA gene. On other moderate favorable C sources, glycerol, galactose and ethanol, asexual development was largely inhibited in $velA^+$ strain but not in velA1 mutant strain. Sexual organs were, however, never produced on acetate. These results suggested that asexual development of wild type is largely dependent on C sources and the velA gene is involved in the repression of asexual development in not-enough-grown (non-competent) thalli resulting in preferential progression of sexual development.

• Journal of Life Science
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• v.21 no.7
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• pp.969-975
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• 2011

We focused on relationship between phytohormones and AtEXPA3 gene in gravitropic response of A. thaliana. RT-PCR analysis shows that AtEXPA3 was highly expressed in actively developing tissues such as leaf, rosette, root and flower tissues. AtEXPA3 gene expression was enhanced by gravistimulation, BR and IAA. Furthermore, decreased gravitropism was observed when treatment of AVG, an ethylene biosynthetic inhibitor, suggesting that ethylene has a gravistimulating effect itself as well as BRs and IAA. Inhibition of gravitropism in AtEXPA3 RNAi mutant suggests that BR, auxin and ethylene are playing roles as regulators of AtEXPA3. In addition, altered gravitropism in BRs signaling mutant (decreased in bri1-301, bak1, and increased BRI-GFP) indicated that BRs signaling mediated the gravitropism. In conclusion, gravitropic responses of Arabidopsis root resulting from root growth were mediated by increased expression of AtEXPA3 gene, which is stimulated by phytohormones.

• Journal of Microbiology and Biotechnology
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• v.32 no.11
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• pp.1485-1495
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• 2022

The development of a yeast strain capable of fermenting mixed sugars efficiently is crucial for producing biofuels and value-added materials from cellulosic biomass. Previously, a mutant Pichia stipitis YN14 strain capable of co-fermenting xylose and cellobiose was developed through evolutionary engineering of the wild-type P. stipitis CBS6054 strain, which was incapable of co-fermenting xylose and cellobiose. In this study, through genomic and transcriptomic analyses, we sought to investigate the reasons for the improved sugar metabolic performance of the mutant YN14 strain in comparison with the parental CBS6054 strain. Unfortunately, comparative whole-genome sequencing (WGS) showed no mutation in any of the genes involved in the cellobiose metabolism between the two strains. However, comparative RNA sequencing (RNA-seq) revealed that the YN14 strain had 101.2 times and 5.9 times higher expression levels of HXT2.3 and BGL2 genes involved in cellobiose metabolism, and 6.9 times and 75.9 times lower expression levels of COX17 and SOD2.2 genes involved in respiration, respectively, compared with the CBS6054 strain. This may explain how the YN14 strain enhanced cellobiose metabolic performance and shifted the direction of cellobiose metabolic flux from respiration to fermentation in the presence of cellobiose compared with the CBS6054 strain.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2022.09a
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• pp.23-23
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• 2022

Rapeseed (Brassica napus L.) is one of the most valuable oilseed crop in the world. It is widely used in various industries, such as food, animal feed, energy and chemical industries. In order to improve the industrial requirements for rapeseed, useful agronomic characteristics (higher yields and disease resistance etc.) and modified oil traits (fatty acid composition and fat content) are important in rapeseed. However, Korea has limiting genetic resources of novel traits in rapeseed. In this research, novel rapeseed mutant genotypes by mutation breeding was developed. The mutant lines were generated by the treatment of the seeds of the original cultivar 'Tamra' with 700 Gy of gamma-ray (⁶⁰Co). Mutants showing varied in flowering time, crude fat content, seed yield and fatty acid content that exhibited stable inheritance of the mutated characteristics from M₅ to M₇ generations were selected. We investigated genetic variation using SNPs identified from GBS analysis in rapeseed mutant lines derived from the gamma-ray, and interactions between the major agronomic and the oil traits. Significantly associated SNP loci were explored along with candidate genes using SNPs obtained by GBS analysis. As a results of association mapping, a total of 322 SNPs were significantly associated with agronomic traits (155 SNPs) and oil traits (167 SNPs). A total of 70 genes were annotated from agronomic characteristics SNPs; among them 7 genes significantly enriched in developmental process, and a total of 70 genes were annotated from crude fat content and fatty acid compositions SNPs; among them, 11genes were significantly enriched in biosynthetic process. These results could be used for the selection of rapeseed cultivar with enhanced qualities and potential economic benefits.

• 한국생물공학회:학술대회논문집
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• 2003.10a
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• pp.600-600
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• 2003

• KSBB Journal
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• v.21 no.2
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• pp.90-95
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• 2006

Escherichia coli harboring pAC-LYCO4 and pDdxs was used for lycopene production. Three wild type strains of E. coli OW1, MG1655, and W3110 were compared with DH5${\alpha}$ used before for lycopene production. Lycopene productivity of E. coli MG1655 was similar to DH5${\alpha}$ and the highest among those wild type strain. Therefore, MG1655 strain was used for random transposon and NTG mutagenesis to increase lycopene productivity. Through transposon mutation, five transposon mutants with increased lycopene productivity were obtained. It was found that genes knocked out by transposon insertion were treB in Tn1 mutant, B2436 in Tn2 mutant, and rfaH in Tn3, 4, and 5 mutants. Lycopene productivity was the highest in Tn4 mutant among the Tn mutants, which was 6-fold and 8-fold higher in lycopene concentration and content, respectively, in comparison with those obtained with wild type strain. NTG4 mutant was acquired with NTG mutation. The highest lycopene productivity of 6 mg/L and 4 mg/g DCW was obtained from the NTG4 mutant when arabinose of 0.013 mM was added for induction of dxs, rate-limiting gene of MEP pathway. The lycopene productivity of NTG4 mutant was increased 18-fold and 12-fold in lycopene concentration and content, respectively when comparing with the wild type strain.

• 한국균학회소식:학술대회논문집
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• 2015.11a
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• pp.23-23
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• 2015

Rice blast disease caused by M. oryzae is the most devastating fungal disease in rice. During the infection process, M. oryzae secretes a large number of glycosyl hydrolase (GH) proteins into the apoplast to digest host cell wall and assist fungal ingress into host tissues. In this study, we identified a novel M. oryze arabinofuranosidase B (MoAbfB) which is secreted during fungal infection. Live-cell imaging exhibited that fluorescent labeled MoAbfB was highly accumulated in fungal invasive structures such as appressorium, tips of penetration peg, biotrophic interfacial complex (BIC), as well as invasive hyphal tip. Deletion of MoAbfB mutants extended biotrophic phase followed by enhanced disease severity, whereas, over-expression of OsMoAbfB mutant induced rapid defense responses and enhanced rice resistance to M. oryzae infection. Furthermore, exogenous treatment of MoAbfB protein showed inhibition of fungal infection via priming of defense gene expression. We later found that the extract of MoAbfB degraded rice cell wall fragments could also induce host defense activation, suggesting that not MoAbfB itself but oligosaccharides (OGs) derived from MoAbfB dissolved rice cell wall elicited rice innate immunity.