• Journal of Microbiology and Biotechnology
• /
• v.25 no.8
• /
• pp.1339-1348
• /
• 2015

Until now, considerable effort has been made to engineer novel nitrogen-fixing organisms through the transfer of nif genes from various diazotrophs to non-nitrogen fixers; however, regulatory coupling of the heterologous nif genes with the regulatory system of the new host is still not well understood. In this work, a 49 kb nitrogen fixation island from P. stutzeri A1501 was transferred into E. coli using a novel and efficient transformation strategy, and a series of recombinant nitrogen-fixing E. coli strains were obtained. We found that the nitrogenase activity of the recombinant E. coli strain EN-01, similar to the parent strain P. stutzeri A1501, was dependent on external ammonia concentration, oxygen tension, and temperature. We further found that there existed a regulatory coupling between the E. coli general nitrogen regulatory system and the heterologous P. stutzeri nif island in the recombinant E. coli strain. We also provided evidence that the E. coli general nitrogen regulator GlnG protein was involved in the activation of the nif-specific regulator NifA via a direct interaction with the NifA promoter. To the best of our knowledge, this work plays a groundbreaking role in increasing understanding of the regulatory coupling of the heterologous nitrogen fixation system with the regulatory system of the recipient host. Furthermore, it will shed light on the structure and functional integrity of the nif island and will be useful for the construction of novel and more robust nitrogen-fixing organisms through biosynthetic engineering.

• Molecules and Cells
• /
• v.38 no.1
• /
• pp.40-50
• /
• 2015

In the interaction between plants and pathogens, carbon (C) resources provide energy and C skeletons to maintain, among many functions, the plant immune system. However, variations in C availability on pathogen associated molecular pattern (PAMP) triggered immunity (PTI) have not been systematically examined. Here, three types of starch mutants with enhanced susceptibility to Pseudomonas syringae pv. tomato DC3000 hrcC were examined for PTI. In a dark period-dependent manner, the mutants showed compromised induction of a PTI marker, and callose accumulation in response to the bacterial PAMP flagellin, flg22. In combination with weakened PTI responses in wild type by inhibition of the TCA cycle, the experiments determined the necessity of C-derived energy in establishing PTI. Global gene expression analyses identified flg22 responsive genes displaying C supply-dependent patterns. Nutrient recycling-related genes were regulated similarly by C-limitation and flg22, indicating re-arrangements of expression programs to redirect resources that establish or strengthen PTI. Ethylene and NAC transcription factors appear to play roles in these processes. Under C-limitation, PTI appears compromised based on suppression of genes required for continued biosynthetic capacity and defenses through flg22. Our results provide a foundation for the intuitive perception of the interplay between plant nutrition status and pathogen defense.

• Journal of Food Hygiene and Safety
• /
• v.36 no.5
• /
• pp.407-417
• /
• 2021

In order to investigate frequency of fungal contamination in ginseng sprout, we collected 18 types of retail ginseng sprouts and analyzed them. Overall frequency of fungal contamination ranged from 113.3 to 174.1% with the highest occurrence of Penicillium spp. Fungal detection rate was significantly higher in moss than in stem, leaf and root of ginseng sprout. Penicillium spp. occurred in leaf and stem with the highest incidence and Fusarium spp., in root. Among Penicillium spp. and Fusarium spp., P. olsonii and F. oxysporum were dominant, respectively. Nine Fusarium species, Aspergillus westerdijkiae, Aspergillus flavus, and 11 Penicillium species were identified by phylogenetic analysis. PCR screening of mycotoxigenic potential revealed that 19 out of 25 isolates tested were positive for respective mycotoxin biosynthetic gene. Two 2 A. flavus and 11 A. westerdijkiae isolates produced varying amount of aflatoxin or ochratoxin A in czapek yeast extract brothsome of which showed high levels of mycotoxin production. These results suggests a need for continuous monitoring and management program to control fungal contamination in the ginseng sprout production chain.

• Korean Journal of Breeding Science
• /
• v.50 no.4
• /
• pp.351-363
• /
• 2018

In ornamental crops, the color and shape of flowers are one of the important traits. Generally, flower colors are determined by accumulating pigments such as carotenoids, flavonoids, and betalains. Among them, flavonoids are responsible for broad ranges of colors. Chrysanthemums are one of the most popular ornamental crops in the world, and there have been many efforts to change their flower color. In chrysanthemum flowers, cyanidin-based anthocyanin confers pink or red color, whereas terpenoid-based carotenoids are mainly responsible for yellow and green colors. However, blue colored chrysanthemums do not occur in nature. To date, there have been attempts to obtain blue or violet-colored chrysanthemum flowers through the introduction of a novel gene for accumulating delphinidin-based anthocyanins, while other studies have reported changing endogenous metabolites through the reconstruction of flavonoid biosynthesis. Since various transcription factors are involved in the regulation of flavonoid biosynthesis, it is important to understand not only the structural genes, but also the transcription factors required for the modification of flavonoid-based flower color. Therefore, in this paper, we describe the flavonoid biosynthetic pathway and its regulation, and review previous studies on the change in flower color through modification of flavonoid biosynthesis. This effort could be an important milestone in successfully achieving the modification of chrysanthemum flower color by means of plant biotechnology.

• Journal of Bio-Environment Control
• /
• v.31 no.4
• /
• pp.332-342
• /
• 2022

Kale (Brassica oleracea var. acephala) is one of the most frequently consumed leafy vegetables globally, as it contains numerous nutrients; essential amino acids, phenolics, vitamins, and minerals, and is particularly rich in glucosinolates. However, the differences in the biosynthesis of glucosinolates and related gene expression among kale cultivars has been poorly reported. In this study, we investigated glucosinolates profile and content in three different kale cultivars, including green ('Man-Choo' and 'Mat-Jjang') and red kale ('Red-Curled') cultivars grown in a vertical farm, using transcriptomic and metabolomic analyses. The growth and development of the green kale cultivars were higher than those of the red kale cultivar at 6 weeks after cultivation. High-performance liquid chromatography (HPLC) analysis revealed five glucosinolates in the 'Man-Choo' cultivar, and four glucosinolates in the 'Mat-Jjang' and 'Red-Curled' cultivars. Glucobrassicin was the most predominant glucosinolate followed by gluconastrutiin in all the cultivars. In contrast, other glucosinolates were highly dependent to the genotypes. The highest total glucosinolates was found in the 'Red-Curled' cultivar, which followed by 'Man-Choo' and 'Mat-Jjang'. Based on transcriptome analysis, eight genes were involved in glucosinolate biosynthesis. The overall results suggest that the glucosinolate content and accumulation patterns differ according to the kale cultivar and differential expression of glucosinolate biosynthetic genes.

• Journal of Food Hygiene and Safety
• /
• v.37 no.4
• /
• pp.277-284
• /
• 2022

To investigate the occurrence of fungi in dried ginseng products, we collected 24 white and 26 red ginseng samples from the retail market. Fungi were detected in 50% and 46% of white and red ginseng samples, respectively. The average level of fungal contamination was 0.5 and 0.2 log₁₀ CFU/g in white and red ginseng, respectively. In white ginseng, Penicillium polonicum, P. chrysogenum, and Rhizopus microsporus dominated with each having an occurrence of 18.2%. In red ginseng, Aspergillus spp. was dominant with an occurrence of 87.6%, with A. chevalieri having the highest occurrence (50%). PCR screening for mycotoxigenic potential showed that the 13 isolates of 4 species (P. polonicum, P. chrysogenum, P. melanoconidium, and A. chevalieri) tested were negative for the citrinin biosynthetic gene. These results show that the samples tested in this study had low risk of mycotoxin contamination. However, there is a possibility of dried ginseng products, such as white and red ginseng, being contaminated with fungi.

• Journal of Ginseng Research
• /
• v.47 no.1
• /
• pp.44-53
• /
• 2023

Background: The genus Panax in the Araliaceae family has been used as traditional medicinal plants worldwide and is known to biosynthesize ginsenosides and phytosterols. However, genetic variation between Panax species has influenced their biosynthetic pathways is not fully understood. Methods: Simultaneous analysis of transcriptomes and metabolomes obtained from adventitious roots of two tetraploid species (Panax ginseng and P. quinquefolius) and two diploid species (P. notoginseng and P. vietnamensis) revealed the diversity of their metabolites and related gene expression profiles. Results: The transcriptome analysis showed that 2,3-OXIDOSQUALENE CYCLASEs (OSCs) involved in phytosterol biosynthesis are upregulated in the diploid species, while the expression of OSCs contributing to ginsenoside biosynthesis is higher in the tetraploid species. In agreement with these results, the contents of dammarenediol-type ginsenosides were higher in the tetraploid species relative to the diploid species. Conclusion: These results suggest that a whole-genome duplication event has influenced the triterpene biosynthesis pathway in tetraploid Panax species during their evolution or ecological adaptation. This study provides a basis for further efforts to explore the genetic variation of the Panax genus.

• Journal of Microbiology and Biotechnology
• /
• v.33 no.4
• /
• pp.552-558
• /
• 2023

Levulinic acid (LA) is a valuable chemical used in fuel additives, fragrances, and polymers. In this study, we proposed possible biosynthetic pathways for LA production from lignin and poly(ethylene terephthalate). We also created a genetically encoded biosensor responsive to LA, which can be used for screening and evolving the LA biosynthesis pathway genes, by employing an LvaR transcriptional regulator of Pseudomonas putida KT2440 to express a fluorescent reporter gene. The LvaR regulator senses LA as a cognate ligand. The LA biosensor was first examined in an Escherichia coli strain and was found to be non-functional. When the host of the LA biosensor was switched from E. coli to P. putida KT2440, the LA biosensor showed a linear correlation between fluorescence intensity and LA concentration in the range of 0.156-10 mM LA. In addition, we determined that 0.156 mM LA was the limit of LA detection in P. putida KT2440 harboring an LA-responsive biosensor. The maximal fluorescence increase was 12.3-fold in the presence of 10 mM LA compared to that in the absence of LA. The individual cell responses to LA concentrations reflected the population-averaged responses, which enabled high-throughput screening of enzymes and metabolic pathways involved in LA biosynthesis and sustainable production of LA in engineered microbes.

• Journal of Microbiology and Biotechnology
• /
• v.33 no.10
• /
• pp.1292-1298
• /
• 2023

PAMB 00755^T, a bacterial strain, was isolated from Korean fir leaves. The strain exhibits yellow colonies and consists of Gram-negative, non-motile, short rods or ovoid-shaped cells. It displays optimal growth conditions at 20℃, 0% NaCl, and pH 6.0. Results of 16S rRNA gene-based phylogenetic analyses showed that strain PAMB 00755^T was most closely related to Sphingomonas chungangi MAH-6^T (97.7%) and Sphingomonas polyaromaticivorans B2-7^T (97.4%), and ≤96.5% sequence similarity to other members of the genus Sphingomonas. The values of average nucleotide identity (79.9-81.3%), average amino acid identity (73.3-75.9%), and digital DNA-DNA hybridization (73.3-75.9%) were significantly lower than the threshold values for species boundaries; these overall genome-related indexes (OGRI) analyses indicated that the strain represents a novel species. Genomic analysis revealed that the strain has a 4.4-Mbp genome encoding 4,083 functional genes, while the DNA G+C content of the whole genome is 66.1%. The genome of strain PAMB 00755^T showed a putative carotenoid biosynthetic cluster responsible for its antioxidant activity. The respiratory quinone was identified as ubiquinone 10 (Q-10), while the major fatty acids in the profile were identified as C_18:1ω7c and/or C_18:1ω6c (summed feature 8). The major polar lipids of strain PAMB 00755^T were diphosphatidylglycerol, phosphatidylethanolamine, sphingoglycolipid, and phosphatidylcholine. Based on a comprehensive analysis of genomic, phenotypic, and chemotaxonomic characteristics, we proposed the name Sphingomonas abietis sp. nov. for this novel species, with PAMB 00755^T as the type strain (= KCTC 92781^T = GDMCC 1.3779^T).