• Korean Journal of Plant Tissue Culture
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• v.26 no.4
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• pp.289-291
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• 1999

Hypocotyl explants from 7 days old seedlings of one $F_1$ hybrid cultivar and two pure lines of cucumber formed embryogenic calli at frequencies of up to 8% when cultured on Murashige and Skoog medium (MS) supplemented with 1 mg/L 2,4-D for 3 weeks. Embryogenic calli gave rise to somatic embryos. When slices of somatic embryos were cultured on the same medium for 4 weeks, they formed embryogenic calli. Embryogenic cell suspension cultures were established with embryogenic calli in MS liquid medium with 1 mg/L 2,4-D. Embryogenic potential of cell suspension cultures was maintained by subculturing every seven days. When the level of 2,4-D in the medium was lowered to 0.2 mg/L by diluting with liquid MS basal medium, embryogenic cell suspension cultures underwent development into numerous somatic embryos. When plated onto MS basal medium, over 95% of somatic embryos developed into plantlets. Plantlets were transplanted to potting soil and grown to maturity.

• Korean Journal of Plant Tissue Culture
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• v.27 no.4
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• pp.245-258
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• 2000

Somatic embryogenesis has become a major tool in the study of plant embryology, as it is possible in culture to manipulate cells of many plant species to produce somatic embryos in a process that is remarkably similar to zygotic embryogenesis. Traditionally, the process has been studied by an examination of the ex vitro factors which influence embryo formation. Later structural, physiological and biochemical approaches have been applied. Host recently, molecular tools are being used. Together, these various approaches are giving valuable information on the process. This article gives an overview of somatic embryogenesis by reviewing information on the morphogenesis, physiology, biochemistry and molecular biology of the process. Topics covered include a brief description of the factors involved in the production of embryogenic cells. Carrot cell suspension is most commonly used, and the development of a high frequency and synchronous system is outlined. At the physiological and biochemical lev-els various topics, including the reactivation of the cell cycle, changes in endogenous growth regulators, amino acid, polyamine, DNA, RNA and protein metabolism, and embryogenic factors in conditioned medium are all discussed. Lastly, recent information on genes and molecular markers of the embryogenic process are outlined. Somatic embryogenesis, the best example of totipotency in plant cells, is not only an important tool in studies in basic biology, but is potentially of equal significance in the micropropagation of economically important plants.

• Journal of Plant Biotechnology
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• v.30 no.4
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• pp.341-346
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• 2003

In an effort to optimize tissue culture conditions for genetic transformation of orchardgrass (Dactylis glomerata L.), an efficient and high-frequency plant regeneration system from seed-derived calli was established. Embryogenic calli induced on MS medium containing 3mg/L 2,4-D and 0.1mg/L BA had significantly improved regeneration ability. Plant regeneration rate was 92％ when embryogenic calli were cultured on N6 medium supplemented with 1mg/L 2,4-D and 3mg/L BA. Among three kinds of medium, MS and N6 medium were optimal for embryogenic callus induction and plant regeneration, respectively. Ho difference in callus induction frequency was observed among four cultivars of orchardgrass, however, "Roughrider" cultivar showed higher regenerability with the frequency of 61％. Addition of maltose to the regeneration medium as a carbon source dramatically increased regeneration frequency up to 69％. A short tissue culture period and high-frequency regeneration system would be beneficial for molecular breeding of orchardgrass through genetic transformation.

• Korean Journal of Plant Tissue Culture
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• v.25 no.1
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• pp.13-19
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• 1998

We have reported previously that intact embryogenic cells can be used instead of protoplasts for electroporation-mediated transformation of zoysiagrass and rice. In this study, conditions of the tissue electroporation were examined to optimize the procedures. Embryogenic cell suspensions were established in liquid MS medium containing 2 mg/L of 2,4-D with embryogenic calluses induced from mature embryos of Z. japonica. The suspension-cultured cell clumps were electroporated with 35S-gusA expression vector DNA, and degrees of DNA introduction into the cells were determined by histological expression rates of the gusA marker gene. DNA transfer into the cell clumps occurred in wide range of voltage (100-400 V) and capacitance (10-1980 $\mu\textrm{F}$), but more in the ranges of 200-300 V and 330-800 $\mu\textrm{F}$ DNA concentrations higher than 6 $\mu\textrm{g}$/mL were adequate for GUS expression of the electroporated cells. DNA transfers were confirmed in all three embryogenic cell lines but only in one out of eleven non-embryogenic lines. Positive GUS expressions occurred with DNAs added even 20-40 h after pulse treatments. As a promoter of gusA, Act1 and Ubi1 were effective 7 and 5 times than 35S respectively in number of GUS expression units on electroporated cell clumps. Embryogenic cell clumps survived and regenerated into plantlets after pulse treatments of wide range of conditions.

• Journal of Plant Biotechnology
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• v.2 no.2
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• pp.109-113
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• 2000

Somatic hybrids were produced by electrofusion between embryogenic callus protoplasts of 'Syougun' mandarin and leaf protoplasts of grapefruit. Hybridity of the two plants was confirmed by leaf morphological characteristics and random amplified polymorphic DNA (RAPD) analysis. The cpDNA analysis using PCR-RFLP could not distinguish those of both parents. These plants showed normal growth and had chromosome number of 27. These unexpected triploid somatic hybrids might be derived from fused cells between diaploid protoplast of embryogenic calli and diploid protoplast of leaf, because polysomaty, a mixture of haploid cells and diploid cells was observed in the lactose medium-pretreated embryogenic calli of 'Syougun' by flow cytomehy analysis.

• Korean Journal of Plant Tissue Culture
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• v.21 no.5
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• pp.281-286
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• 1994

The hormonal regulation of organ differentiation was investigated in the tissue culture of sweet potato. Embryogenic callus was induced from shoot tips cultured on MS medium supplemented with 1 mg/L 2,4-D. When embryogenic callus was transferred to medium containing 0.1 mg/L GA$_4$, it proliferation was stimulated. The callus gave rise to plantlets when cultured on medium containing 0.1 mg/L BA. Addition of 0.1 mg/L jasmonic acid or 0.01 mg/L brassinolide to medium was effective for the development of healthy normal plantlets.

• Korean Journal of Medicinal Crop Science
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• v.4 no.2
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• pp.126-131
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• 1996

Plant regeneration from the stem tissue of Houttuynia cordata Thunberg was investigated. The medium supplemented with the combination of 2, 4-D 1 mg/L and kinetin 0. 5 mg/L was the most effective for the embryogenic callus formation. The internode segment produced more callus formation than the leaf segment. ${\frac{1}{2}}\;MS$ medium was the most effective for the embryogenic callus formation. The medium supplemented with the 1% activated charcoal produced the whole plant directly without the callus formation from the nodes. The medium supplemented with the combination of NAA 0. 2 mg/L and BA 1 mg/L was the most effective for the plant regeneration from the embryogenic callus.

• Korean Journal of Plant Tissue Culture
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• v.27 no.3
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• pp.213-217
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• 2000

To investigate the cucumber regeneration from embryogenic calli, shoot tips of aseptically-grown cucumber seedlings were used as explants for establishing tissue cultures. Growth and differentiation of callus were studied by using Murashige and Skoog's (MS) medium containing 0.5 to 2 mg/L 2,4-D. Plantlets were induced from shoot tip culture on the plant growth regulators-free MS medium. Non-embryogenic calli and viscous calli were induced on the medium supplemented with 0.5 to 2 mg/L 2,4-D, but embryogenic callus was not induced on the same medium. Segments (ca. 5∼10 mm) of aseptically-grown hypocotyl from five to seven days old seedlings after germination were placed on MS medium supplemented with 1 mg/L 2,4-D for 50 days. Embryogenic calli and embryoids were induced only from the seedlings grown in dark condition, and hypocotyl was placed on the media explanted in light condition. Foully-five point one percent of white fragile calli and 0.6% yellowish compact calli formed roots. Yellowish callus lines were investigated to have a considerably higher concentration of crude proteins than white callus lines. Plantlets derived from embryogenic calli or embryoids have been transferred to pots containing sterile vermiculite and perlite. Normal fruits were harvested from nutrient culture on aggregated hydroponics in the F-clean house.

• Journal of Plant Biotechnology
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• v.31 no.4
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• pp.267-271
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• 2004

Transformed sweetpotato (Ipomoea batatas (L.) Lam. cv. Yulmi) plants were developed from embryogenic calli following Agrobacterium tumefaciens-mediated transformation. A. tumefaciens strain EHA105/pCAMBIA2301 harboring genes for intron $\beta$-glucuronidase (GUS) and kanamycin resistance. Transient expression of GUS gene was found to be higher when embryogenic calli were co-cultivated with Agrobacterium for 2 days. The co-cultured embryogenic calli transferred to selective MS medium containing 1mg/L 2,4-D, 100mg/L kanamycin, and 400mg/L claforan. These embryogenic calli were subcultured to the same selection medium at 4 weeks interval. Kanamycin-resistant calli transferred to hormone-free MS medium with kanamycin gave rise to somatic embryos and then converted into plantlets in the same medium. Southern blot analysis confirmed that the GUS gene was inserted into the genome of the sweetpotato plants. A histochemical assay revealed that the GUS gene was preferentially expressed in the leaf, petiole, and vascular tissue and tip of root.

• Korean Journal of Plant Tissue Culture
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• v.27 no.2
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• pp.149-154
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• 2000

Embryogenic suspension cultures were initiated using embryogenic callus from immature inflorescence explants (Aralia cordata Thunb.) cultured on solid MS medium containing 1 mg/L 2,4-D for 8 weeks and then the embryogenic callus was proliferated in liquid MS medium containing 1 mg/L 2,4-D. After sieving the suspensions (pore size 270$\mu$m), embryogenic cells were cultured in liquid MS medium with cytokinins (kinetin, BA, zeatin) for two weeks. When the embryogenic cells were transferred to liquid MS basal medium, primary somatic embryos were developed after 5 weeks of culture. Secondary embryos were developed directly from the primary torpedo and cotyledonary embryos cultured in solid MS basal medium. Frequency of secondary embryogenesis was higher on medium containing 2 mg/L kinetin than the other cytokinins. Plant regeneration was highly recorded by placing secondary cotyledonary embryos induced from primary cotyledonary embryos in MS medium containing 2 mg/L kinetin or 2 mg/L zeatin (25.4% and 28.6%, respectively). The plant regeneration from secordary embryos was prohibited by tertiary embryogenesis.