Under appropriate in vivo or in vitro conditions, certain somatic plant cells have the capability to initiate embryogenic development (somatic embryogenesis). Somatic embryogenesis provides an unique experimental model to understand the molecular and cellular bases of developmental plasticity in plants. In the last few years, the application of modern experimental techniques, as well as the characterization of Arabidopsis embryogenesis mutants, have resulted in the accumulation of novel data about the acquisition of embryogenic capabilities by somatic plant cells. In this review, we summarize relevant experimental observations that can contribute to the description and definition of a transitional state of somatic cells induced to form totipotent, embryogenic cells. During this somatic-to-embryogenic transition, cells have to dedifferentiate, activate their cell division cycle and reorganize their physiology, metabolism and gene expression patterns. The roles of stress, endogenous growth regulators and chromatin remodelling in the coordinated reorganization of the cellular state are especially emphasized.

http://www.cas.miamioh.edu/~meicenrd/pdevlmnt/feheretal2003.pdf

Transition of somatic plant cells to an embryogenic state

In spite of the importance attained by somatic embryogenesis and of the many studies that have been conducted on this developmental process, there are still many aspects that are not fully understood. Among those features, the involvement of plant hormones and plant growth regulators on deTermining the conversion of somatic onto embryogenic tissues, and on allowing progression and maturation of somatic embryos, are far away from being completely comprehended. Part of these difficulties relies on the frequent appearance of contradictory results when studying the effect of a particular stimulus over a specific stage in somatic embryogenesis. Recent progress achieved on understanding the interaction between exogenously added plant growth regulators over the concentration of endogenous hormones, together with the involvement of sensitivity of the tissues to particular hormone groups, might help clarifying the occurrence of divergent patterns in somatic embryogenesis, and in tissue culture in general. The aspects described above, emphasizing on the effect of the concentration of plant hormones and of the addition of plant growth regulators during the different phases of somatic embryogenesis, will be reviewed in this paper. Citations will be limited to review articles as much as possible and to individual articles only in those cases in which very specific or recent information is presented.

Involvement of plant hormones and plant growth regulators on in vitro somatic embryogenesis

Plants are a tremendous source for the discovery of new products of medicinal value for drug development. Today several distinct chemicals derived from plants are important drugs currently used in one or more countries in the world. Many of the drugs sold today are simple synthetic modifications or copies of the naturally obtained substances. The evolving commercial importance of secondary metabolites has in recent years resulted in a great interest in secondary metabolism, particularly in the possibility of altering the production of bioactive plant metabolites by means of tissue culture technology. Plant cell culture technologies were introduced at the end of the 1960's as a possible tool for both studying and producing plant secondary metabolites. Different strategies, using an in vitro system, have been extensively studied to improve the production of plant chemicals. The focus of the present review is the application of tissue culture technology for the production of some important plant pharmaceuticals. Also, we describe the results of in vitro cultures and production of some important secondary metabolites obtained in our laboratory.

/pdf/studies-on-the-production-of-some-important-secondary-2drqfb9nvf.pdf

Studies on the production of some important secondary metabolites from medicinal plants by plant tissue cultures

Somatic embryogenesis is the developmental process by which somatic cells undergo restructuring to generate embryogenic cells. These cells then go through a series of morphological and biochemical changes that result in the formation of a somatic or non-zygotic embryo capable of regenerating plants. Somatic embryogenesis represents a unique developmental pathway that includes a number of characteristic events: dedifferentiation of cells, activation of cell division, and reprogramming of their physiology, metabolism, and gene expression patterns. Valuable studies have elucidated the developmental processes pertaining to the control parameters of somatic embryogenesis. These studies have emphasized the transitional state from somatic to embryogenic cells, identified differentially expressed genes in nonembryogenic and embryogenic calli, isolated varieties of genes that are likely involved in the embryogenic pathway, compared specific gene products that accumulate during different stages of somatic embryogen...

Regulation of Somatic Embryogenesis in Higher Plants

The components of plant tissue culture media II. Organic additions, osmotic and pH effects, and support systems

http://directory.umm.ac.id/Data%20Elmu/jurnal/P/PlantScience/PlantScience_Elsevier/Vol160.Issue1.2000/5498.pdf

Cytokinin-induced somatic embryogenesis and plant regeneration in Corydalis yanhusuo (Fumariaceae) - a medicinal plant.

An efficient method for regeneration of entire plants via somatic embryogenesis in Corydalis yanhusuo using tuber-derived callus has been developed. Primary callus was obtained by culturing tuber explants on Murashige and Skoog’s (MS) (1962) medium supplemented with 2.0 mg l−1 N6-benzyladenine (BA) and 0.5 mg l−1 α-naphthaleneacetic acid (NAA) in darkness for one month. Somatic embryos were induced by subculturing the primary callus on MS medium supplemented with 0.5–4.0 mg l−1 BA, kinetin, or zeatin, within 2 weeks of culture in light. Rooting in the embryos with well developed cotyledonary leaves was achieved by transferring them to half-strength liquid MS medium supplemented with 1.0 mg l−1 zeatin riboside for three weeks. Converted somatic embryos were cultured on half-strength MS medium supplemented with 6% (w/v) sucrose, and with 0.5–10.0 mg l−1 abscisic acid (ABA), paclobutrazol, or ancymidol, 0.5–5.0 mg l−1 gibberellic acid (GA3) and 15–100 mg l−1 polyethylene glycol (PEG) 4000 for further development of plantlets and tuber formation in vitro. Recurrent somatic embryogenesis has been observed in the region at the junction of cotyledon and root when the converted somatic embryos were cultured on MS basal medium supplemented with 0–10 mg l−1 ABA. The use of liquid MS basal medium with 0.1 mg l−1 GA3 enhanced embryo conversion within fifteen days of culture. Phenotypically normal plants were recovered from converted somatic embryos and the plants showed well-developed tuber formation and in vitro flowering after 4 months of culture. Also, the effects of 0.5–5 mg l−1 ABA, paclobutrazol and 0.5–2 mg l−1 ancymidol, 0.5–5 mg l−1 GA3 and 15–100 mg l−1 PEG 4000 supplemented in half-strength MS medium on the production of the two major protoberberine-type alkaloids (D,L-tetrahydropalmatine and D-corydaline) by the tubers of somatic embryo-derived plants of C. yanhusuo were examined. The high performance liquid chromatography (HPLC) analysis revealed that the contents of D,L- tetrahydropalmatine and D-corydaline in the tubers of somatic embryo-derived plants were greater than the marketed crude drug and varied with growth regulator / PEG-4000 treatment and the age of the plant.

Y. L. Lee

Papers

Cytokinin-induced somatic embryogenesis and plant regeneration in Corydalis yanhusuo (Fumariaceae) - a medicinal plant.

Tissue culture of Corydalis yanhusuo (Fumariaceae) and its medicinal compound production from somatic embryo-derived plants