Esterases as a marker for growth of BY-2 tobacco cells and early somatic embryos of the Norway spruce

Growth is one of the basic properties of biological systems. The methods which are commonly used for the determination of growth are usually difficult and not very accurate. In the present work we decided to use esterase activity as a growth marker in tobacco suspension culture (BY-2 line) and in early somatic embryos of Norway spruce (clone 2/32) grown on a semi-solid medium. Esterase activity correlates well with the classical growth characteristics of BY-2 and spruce early somatic embryos. Determination of esterase activity is based on spectrophotometric and spectrofluorimetric detection of reaction products, which arise from the enzymatic hydrolysis of two substrates (p -nitrophenyl acetate and fluorescein diacetate) by esterase. The spectrophotometric method enabled us to detect approximately 10⁴ BY-2 cells and 25 spruce embryos whereas the more sensitive spectrofluorimetric method allowed us to detect approximately 800 BY-2 cells and 5 early somatic embryos of Norway spruce.     

Synchronization of somatic embryogenesis from carrot cells at high frequency as a basis for the mass production of embryos

Synchronization of somatic embryogenesis at high frequency is a useful system for the mass production of embryos. Many attempts have been carried out, however, it was difficult to obtain the system in which most of the initial embryogenic cells or cell clusters synchronously differentiate to embryos. In carrot suspension cultures, high frequency, synchronous embryogenesis systems (following three systems) have been established.(1) Small spherical single cells from suspension cultures obtained by sieving and density gradient centrifugation in Percoll solutions differentiated to embryogenic cell clusters at high frequency when they were cultured in a medium containing 2,4-dichlorophenoxyacetic acid (0.05 micromolar), zeatin (1 micromolar) and mannitol (0.2 molar). (2) Embryogenic cell clusters from suspension cultures obtained by sieving, density gradient centrifugation in Ficoll solutions, and subsequent centrifugation at a low speed for a short time synchronously differentiated to embryos, especially globular embryos at high frequency, when they were cultured in a medium containing zeatin (0.1 micromolar) but no auxin. (3) Embryogenic cell clusters obtained by above method are cultured at cell densities of 2×10³ cell clusters ml^-1. Globular embryos which were sieved from embryos induced synchronously differentiated to torpedo-shaped embryos at high frequency when they were cultured at densities below 150 globular embryos ml^-1.Using these systems, the whole process of embryogenesis from single cells to whole plants could be synchronously induced at high frequency.Abbreviations ABA abscissic acid - 2,4-d 2,4-dichlorophenoxyacetic acid - GA₃ gibberellin A₃ - IAA indoleacetic acid - NAA naphthylacetic acid     

Production of eleutherosides in in vitro regenerated embryos and plantlets of <Emphasis Type="BoldItalic">Eleutherococcus chiisanensis</Emphasis>

High frequency somatic embryogenesis of Eleutheorcoccus chiisanensis was achieved through suspension culture of embryogenic cells in hormone-free Murashige and Skoog liquid medium supplemented with 30 g sucrose l⁻¹. Cotyledonary somatic embryos were germinated and converted into plantlets using 20 μM gibberellic acid which were then grown in a 10 l airlift bioreactor. HPLC analysis revealed the accumulation of eleutheroside B, E and E1 in the embryos and plantlets. Thus mass production of embryos and plantlets of E. chiisanensis can be achieved in liquid cultures and the biomass produced may become an alternative source of eleutherosides.     

Acquisition of embryogenic potential in carrot cell-suspension cultures

Embryogenic suspension cultures of domesticated carrot (Daucus carota L.) are characterized by the presence of proembryogenic masses (PEMs) from which somatic embryos develop under conditions of low cell density in the absence of phytohormones. A culture system, referred to as starting cultures, was developed that allowed analysis of the emergence of PEMs in newly initiated hypocotyl-derived suspension cultures. Embryogenic potential, reflected by the number of FEMs present, slowly increased in starting cultures over a period of six weeks. Addition of excreted, high-molecular-weight, heat-labile cell factors from an established embryogenic culture considerably accelerated the acquisition of embryogenic potential in starting cultures. Analysis of [³⁵S]methionine-labeled proteins excreted into the medium revealed distinct changes concomitant with the acquisition of embryogenic potential in these cultures. Analysis of the pattern of gene expression by in-vitro translation of total cellular mRNA from starting cultures with different embryogenic potential and subsequent separation of the [³⁵S]methionine-labeled products by two-dimensional polyacrylamide gel electrophoresis demonstrated a small number of abundant in-vitro-translation products to be present in somatic embryos and in embryogenic cells but absent in nonembryogenic cells. Several other in-vitro-translation products were present in explants, non-embryogenic and embryogenic cells but were absent in somatic embryos. Hybridization of an embryoregulated complementary-DNA sequence, Dc3, to RNA extracted from starting cultures showed that the corresponding gene is expressed in somatic embryos and PEMs but not in non-embryogenic cells.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - cDNA complementary DNA - PAGE polyacrylamide gel electrophoresis - PEM proembryogenic mass     

Investigation of enhancement of two processes, sedimentation and conjugation, when bacteria are concentrated in ultrasonic standing waves

Cells aggregate and can be recovered from suspension when exposed to an ultrasonic standing wave field. The acoustic force on individual cells in a standing wave decreases with particle volume. A plane ultrasonic field generated by a transducer driven at 3.3 MHz was used here to investigate the removal of Escherischia coli, cells with dimensions of the order of 1.0 m, from batch suspension by sedimentation over a range of concentrations (10³ to 10¹⁰ cells ml^–1). Cell removal efficiencies greater than 90% were achieved at initial concentrations of 10¹⁰ cells ml^–1. Removal efficiencies decreased gradually to zero, as initial bacterial concentration was reduced to 10⁷ cells ml^–1. It was found that, when low concentrations of E. coli (10³ to 10⁵ cells ml^–1) were added to suspensions of larger particles (i.e. yeast cells) that were of sufficient concentration to form aggregates in the sound field, E. coli could be harvested to an efficiency of 40%. The results imply that the E. coli became trapped and sediment with aggregates of larger particles. Some strains of bacteria are capable of DNA transfer by conjugation. The transfer rate of E. coli RP4 plasmid is order of magnitudes greater when conjugation occurs on solid medium rather than in liquid suspension. We have investigated whether the conjugation rate would also be higher in ultrasonically induced E. coli clumps than in free suspension. The donor strain was mixed with a recipient strain of E. coli, then sonicated in a capillary at 4.6 MHz in a tubular transducer for 5 min. The bacteria aggregated successfully. Results showed a three-fold increase in the rate of conjugation compared to a liquid mating control.     

Embryogenic cell suspensions of Triticum aestivum x Leymus angustus F1 hybrids: characterization and plant regeneration

Summary Embryogenic cell suspension cultures were established from Triticum aestivum X Leymus angustus F₁ hybrids, using compact nodular calli derived from inflorescence segments. Calli originating from leaf segments did not give rise to stable cell suspensions. Growth measurements of the cell suspensions revealed that they continued rapid growth up to 10 days after subculturing. Flow cytometric studies of the cell cycle over a 7 day culture period showed that the majority of cells were in G₁ phase while the rest were either in S or G₂. During the 7 days of culture, no significant differences in DNA distribution patterns were observed. The cells from suspension cultures produced somatic embryos when they were transferred to different solid media. The embryos germinated and gave rise to plantlets which were successfully rooted and transferred to soil.     

紫茉莉悬浮细胞培养体系的建立

为建立紫茉莉(Mirabilis jalapa L.)悬浮细胞培养体系,以紫茉莉无菌苗叶片诱导的愈伤组织为材料,筛选紫茉莉悬浮细胞的适宜培养体系。结果表明,紫茉莉愈伤组织在MS+2,4-D 1 mg L-1+KT 0.5 mg L-1的液体培养基中悬浮继代培养3~4次,能得到稳定的悬浮细胞系。培养基的pH值为5.5~5.9,蔗糖浓度为30 g L-1更适合悬浮细胞的生长。紫茉莉悬浮细胞的生长曲线大致呈S型。最佳继代培养时间是10 d,培养液的体积为40 mL时,接种量为7.5 mL,可以较好地保持悬浮细胞系。1 L培养液中可提取分泌蛋白(0.42±0.15) g。这些有助于对悬浮细胞提取分泌蛋白的研究。     

Somatic embryogenesis from cell suspension cultures in Carica candamarcensis

Cell suspension cultures of Carica candamarcensis derived from hypocotyl calli were tested concerning their in vitro embryogenic capacity to improve asexual propagation rates in this species. Somatic embryos developed in culture from cells in suspension or from microcalli. Responses were affected by nutrient media and phytohormones used. Best results were obtained by growing the cells in suspension in Nitsch and Nitsch medium containing naphthaleneacetic acid and then plating them upon the same medium containing benzyladenine, or combinations of both hormones.     

Plant regeneration from protoplasts of a commercial Asian long-grain javanica rice

A reproducible plant regeneration system has been developed for protoplasts from embryogenic cell suspension cultures of the commercial Asian long-grain javanica rice, Oryza sativa cv. Azucena. Protoplasts were isolated routinely from cell suspensions with yields of 5.5–12.0 × 10⁶ g^-1 fresh weight. A membrane filter nurse-culture method was adopted and was essential to support sustained mitotic division of protoplast-derived cells, leading to cell colony formation. The protoplast plating efficiency was higher when suspension cells of Lolium multiflorum, rather than those of the japonica rice O. sativa L. cv. Taipei 309, were employed as nurse cells. A two-step shoot regeneration procedure, in which protoplast-derived calli were cultured initially on medium semi-solidified with 1% (w/v) agarose followed by culture on medium containing 0.4% (w/v) agarose, induced plant regeneration from protoplast-derived calli. Fifteen percent of protoplast-derived tissues regenerated shoots; tissues not subjected to this treatment failed to develop shoots.     

Factors influencing <Emphasis Type="Italic">in vitro</Emphasis> regeneration from protoplasts of wild cotton (<Emphasis Type="Italic">G. klotzschianum</Emphasis> A) and RAPD analysis of regenerated plantlets

Plants of a diploid wild cotton species (G. klotzschianum A.) were efficiently regenerated from protoplasts isolated from immature somatic embryos and suspension cultures by studying various factors affecting regeneration. Purified protoplasts were cultured with the density of 2–10×10⁵ ml⁻¹, and the medium was k₃ inorganic salts with modified KM₈P organic compositions, supplemented with several combinations of PGRs. Calluses were formed from protoplasts of suspension cultures and immature somatic embryos. The influences of carbon sources and GA₃ on callus differentiation and somatic embryo germination were analyzed. Somatic embryos germinated normally and formed regenerated plantlets. Regenerated plantlets were transferred to the soil and seeds were obtained. Random amplified polymorphic DNA (RAPD) analysis using 80 arbitrary oligonucleotide 10-mers showed 23 primers that gave 74 clear reproducible bands, with amplification products being monomorphic for 14 tested plantlets. A total of 1036 bands obtained exhibited no aberration in RAPD banding patterns in the 14 plants. Plants regenerated via somatic embryogenesis from the diploid cotton protoplasts have genetic homogeneity.     

Plantlet regeneration via somatic embryogenesis from subcultured callus of mature embryos ofPicea abies (Norway spruce)

Summary Embryogenic callus was initiated from radicles of mature embryos removed from imbibed seeds (24 h). Embryogenic and other nonembryogenic types of callus proliferated on a modified half-strength Murashige-Skoog medium (MS) basal medium (BM) supplemented withmyo-inositol, casein hydrolysate (CH), L-glutamine (gln) and growth regulators kinetin (KN), N⁶-benzyladenine (BAP) each (20×10⁻⁶ M), 2,4-dichlorophenoxyacetic acid (2,4-D) (50×10⁻⁶ M) Embryogenic callus bearing suspensor-like cells in a mucilaginous gel matrix was isolated and maintained by subculture every 10 to 12 days on BM with KN, BAP each (2×10⁻⁶ M) and 2,4-D (5×10⁻⁶ M). Somatic embryos developed spontaneously from the callus on this medium at 23±1° C. Closer examination revealed that numerous polyembryonic clusters, comprised of elongated cells (suspensors) and small dense cells with large nuclei (somatic embryos), occurred in the viscous gel. When this enriched embryonal-suspensor mass was subcultured to low 2,4-D (1×10⁻⁶ M), globular embryos developed by 40 to 60 days. Upon transfer to a liquid medium without growth regulators, the embryos elongated and developed cotyledons and shoots with needles. Plantlet development was completed by 30 days in a basal medium without CH, gln and growth regulators. The total culture time was 150 days. Approximately 40±10 embryos were formed from 500 mg of initial callus. Somatic embryogenesis became aberrant if embryos remained attached to the callus mass and were not subcultured within 10 to 12 days according to the described protocol. Somatic embryos were encapsulated in an alginate gel and stored at 4° C for nearly two months without visible adverse effects on viability. Editor's Statement This paper presents advances in the in vitro regeneration of a commercially useful plant species from stored seeds. In addition, data is presented on short-term storage of the plantlets, and long-term proliferation of the embryonal mass in vitro.     

Calcium increases the yield of somatic embryos in carrot embryogenic suspension cultures

An upward shift in the concentration of calcium present in the medium during somatic embryogenesis increased the number of embryos produced approximately two-fold. This was observed when embryogenic suspension cells grown in 2,4-D medium with the normal calcium concentration of 10^–3 M were transferred to hormone-free medium containing 10^–2 M calcium and when embryogenic suspension cells grown in 2,4-D medium containing 10^–4 M calcium were transferred to hormone-free medium with 10^–3 M calcium. At calcium concentrations between 6·10^–3 and 10^–2 M globular stage somatic embryos were found in cultures supplemented with 2·10^–6 M of 2,4-D indicating that elevated calcium counteracts the inhibitory effect of 2,4-D on somatic embryogenesis. No qualitative changes were found in the pattern of extracellular polypeptides as a result of growth and embryogenesis in media with different calcium concentrations.     

Enhancing the frequency of somatic embryogenesis following <Emphasis Type="Italic">Agrobacterium</Emphasis>-mediated transformation of immature cotyledons of soybean [<Emphasis Type="Italic">Glycine max</Emphasis> (L.) Merrill.]

Summary A characteristic phenotype of highly embryogenic explants along with the location of embryogenesis- and transformation-competent cells/tissues on immature cotyledons of soybean [Glycine max (L.) Merrill.] under hygromycin selection was identified. This highly embryogenic immature cotyledon was characterized with emergence of somatic embryos and incidence of browning/necrotic tissues along the margins and collapsed tissues in the mid-region of an explant incubated upwards on the selection medium. The influences of various parameters on induction of somatic embryogenesis on immature cotyledons following Agrobacterium tumefaciens-mediated transformation and selection were investigated. Using cotyledon explants derived from immature embryos of 5–8 mm in length, a 1∶1 (v/v; bacterial cells to liquid D40 medium) concentration of bacterial suspension and 4-wk cocultivation period significantly increased the frequency of transgenic somatic embryos. Whereas, increasing the infection period of explants or subjecting explants to either wounding or acetosyringone treatments did not increase the frequency of transformation. An optimal selection regime was identified when inoculated immature cotyledons were incubated on either 10 or 25 mgl⁻¹ hygromycin for a 2-wk period, and then maintained on selection media containing 25 mgl⁻¹ hygromycin in subsequent selection periods. However, somatic embryogenesis was completely inhibited when inoculated immature cotyledons were incubated on a kanamycin selection medium. These findings clearly demonstrated that the tissue culture protocols for transformation of soybean should be established under both Agrobacterium and selection conditions.     

Plant regeneration from zygotic embryo-derived embryogenic cell suspension cultures of Ranunculus kazusensis

Culture conditions for high frequency plant regeneration via somatic embryogenesis from cell suspension cultures of Ranunculus kazusensis are described. Zygotic embryos formed white nodular structures and pale-yellow calluses at a frequency of 84.9% when cultured on half-strength Schenk and Hildebrandt (SH) medium supplemented with 0.1 mg l⁻¹ 2,4-dichlorophenoxyacetic acid (2,4-D). However, the frequency of white nodular structure and off-white callus formation decreased with an increasing concentration of 2,4-D up to 10 mg l⁻¹, when the frequency reached 25%. Cell suspension cultures were established from zygotic embryo-derived pale-yellow calluses using half-strength SH medium supplemented with 0.1 mg l⁻¹ of 2,4-D. Upon plating onto half-strength SH basal medium, over 90% of cell aggregates gave rise to numerous somatic embryos and developed into plantlets. Regenerated plantlets were successfully transplanted to potting soil and grown to maturity at a survival rate of over 90% in a growth chamber. The plant regeneration system established in this study can be applied to mass propagation and conservation of this species.     

Growth, metabolism and baculovirus production in suspension cultures of an Anticarsia gemmatalis cell line

The UFL-AG-286 cell line, established from embryonic tissue of the lepidopteran insect Anticarsia gemmatalis, has been identified as a good candidate to be used as a cellular substrate in the development of a process for in vitro production of the Anticarsia gemmatalis multicapsid nucleopolyhedrovirus, a baculovirus widely used as bioinsecticide. In order to characterize the technological properties of this cell line and evaluate its feasibility to use it for the large-scale production of Anticarsia gemmatalis multicapsid nucleopolyhedrovirus, UFL-AG-286 cells were adapted to grow as agitated suspension cultures in spinner-flasks. Batch suspension cultures of adapted cells in serum-supplemented TC-100 medium grew with a doubling time of about 29 h and reached a maximum cell density higher than 3.5 × 10⁶ viable cells ml⁻¹. At the end of the growth period glucose was completely depleted from the culture medium, but l-lactate was not produced. Amino acids, with the exception of glutamine, were only negligibly consumed or produced. In contrast to other insect cell lines, UFL-AG-286 cells appeared to be unable to synthesize alanine as a metabolic way to dispose the by-product ammonia. The synchronous infection of suspension cultures with Anticarsia gemmatalis multicapsid nucleopolyhedrovirus in the early to medium exponential growth phase yielded high amounts of both viral progenies per cell and reduced the specific demands of UFL-AG-286 cells for the main nutrients.     

A method for establishing cell lines fromDrosophila melanogaster embryos

Summary A simple method is presented for establishing continuous cell lines fromDrosophila melanogaster embryos. Subculturing is performed after the first 8 weeks and at 2-week intervals therafter. Initial plating densities of 5×10⁴ to 5×10⁵ cells per cm² are required for maintaining the subcultures. Cell lines were established from wild-type embryos, from embryos bearing chromosomal rearrangements and from embryos bearing recessive mutations. Permanent lines have doubling times of 24 to 48 hr and have been maintained for as long as 13 months and 25 subcultures. Supported in part by NSF grant BMS75-02138 and NIH grant NS09330 to. R. Seecof.     

Fertile plant regeneration from protoplasts of meadow fescue (Festuca pratensis Huds.)

Suspension cultures from mature embryo-derived compact callus were initiated in seven meadow fescue (Festuca pratensis Huds.) cultivars. Four to six months after initiation, embryogenic suspension cultures with a moderate growth rate were established from three of them (cvs. Barmondo, Belimo and Leopard). These suspension cultures showed the capacity, maintained over six months, to regenerate green plants which could be grown to maturity under greenhouse conditions.Morphogenic suspension cultures from single genotypes of three F. pratensis cultivars (cvs. Barmondo, Belimo and Leopard) yielded large numbers of protoplasts, which upon culture in agarose beads using nurse cells formed microcalli with an overall plating efficiency in the range of 10^-3 to 10^-4. Mature plants were reproducibly regenerated and established in soil, from such protoplasts during a period of six months. The regeneration of fertile plants from protoplasts derived from suspension cultures of meadow fescue and its implications on gene transfer technology for this species are discussed.Abbreviations 2,4-D 2,4-dichlorophenoxy-acetic acid.     

Multiplication and germination of somatic embryos of American ginseng derived from suspension cultures and biochemical and molecular analyses of plantlets

Summary Seedlings from 11 seed sources (lines) of American ginseng from different geographic regions were evaluated on Murashige and Skoog medium (MS) containing 10 μM α-naphthaleneacetic acid (NAA) and 9 μM 2,4-dichlorophenoxyacetic acid (2,4-D) for callus development and somatic embryo formation. Leaf and stem explants callused at a frequency of 18.2–100%, while somatic embryos were produced from these calluses at a frequency of 25–87.5% after 5 mo. Suspension cultures of nine lines were established by transferring embryogenic callus to MS liquid medium with NAA and 2,4-D at 2.5 and 2.25 μM, respectively, and maintained by subcultures every 8 wk. Globular somatic embryos from these cultures were germinated on half-strength MS containing 1% activated charcoal, and roots >5 mm in length developed within 3 wk. A 7-d exposure to 3 μM gibberellic acid and 5 μM 6-benzylaminopurine significantly enhanced shoot development and promoted further root development. The chromosome number, profiles of the common triterpenoid saponins (ginsenosides), and random amplified polymorphic DNA (RAPD) banding patterns in plantlets derived from suspension culture were compared to those of zygotic seedlings. The chromosome number in root tip cells and suspension cultured cells was 48. Patterns of the six major ginsenosides, determined by thin-layer chromatography, in leaves of tissue culture-derived plantlets were identical to those in seedlings. RAPD patterns among plantlets originating from the same tissue-cultured line were mostly identical; however, altered patterns were observed in some lines that had been maintained in suspension culture for almost 4 yr. The results from this study indicate that propagation of desired ginseng genotypes in suspension culture can be achieved, and that biochemical and molecular markers can be used for authentication of resulting plantlets.     

The isolation of functional pole cells from theDrosophila melanogaster maternal effect mutantmat(3)1

Summary A procedure for pole cell isolation has been developed that takes advantage of theDrosophila melanogaster maternal effect mutantmat(3) 1. Embryos derived from homozygousmat(3)1 mothers form exclusively pole cells. By outcrossing we could substantially increase the expressivity of the original mutant stock. We further introduced theTM8 balancer chromosome, which carries the dominant temperature sensitive mutationDTS-4. This allows the accumulation of large homozygousmat(3) 1 fly populations by eliminating the heterozygous flies at the restrictive temperature.Early embryos were mechanically fragmented and the cells were isolated by means of metrizamide step gradients. The isolated cells were demonstrated to exhibit the various ultrastructural and histochemical characteristics of pole cells. The isolated cells were transplanted into genetically marked host embryos. The germ line mosaics that were obtained indicate that the isolated cells represent functional pole cells.Proteins synthesized by the isolated pole cells during short term in vitro labelling with³⁵S-methionine were compared to the proteins synthesized by blastoderm cells fromOregon-R embryos. At least one protein could be demonstrated in the pole cell samples that is not synthesized byOregon-R blastoderm cells.The method allows a fast and gentle isolation of highly enriched pole cell populations which are a prerequisite for the biochemical analysis of germ cell determination and differentiation.     

Cold-enhanced somatic embryogenesis in cell suspension cultures of Astragalus adsurgens Pall.: relationship with exogenous calcium during cold pretreatment

The inter-relationship between exogenous calcium (Ca²⁺) during cold pretreatment and cold-enhanced somatic embryogenesis was investigated using cell suspension cultures of Astragalus adsurgens Pall. Cell suspension was obtained from embryogenic callus and could be induced to form somatic embryos in the differentiation medium. Suspension cells, after cold-treatment at 8 °C for 2 to 3 wk, displayed an enhanced capacity for somatic embryogenesis as compared to those without cold pretreatment. Longer cold pretreatment (> 4 wk) resulted in the inhibition of somatic embryogenesis. The enhanced embryogenic response of cells to cold pretreatment was dependent on the Ca²⁺ level in the pretreatment medium. Ca²⁺ levels below 1 mM suppressed the cold-enhanced response. Addition of lanthanum into the pretreatment medium completely abolished the cold induced enhancement of somatic embryogenesis. These results suggest that embryogenic cells require a minimal concentration of Ca²⁺ during pretreatment for the expression of this cold-enhanced capacity for somatic embryogenesis in A.adsurgens and the influx of exogenous Ca²⁺ during pretreatment might also be involved.