Expression Of Somatic Embryogenesis Research Articles

Differential carbohydrate metabolism conducts morphogenesis in embryogenic callus of Hevea brasiliensis (Mull. Arg.)

Somatic embryogenesis in Hevea is stimulated when the embryogenesis induction medium contains maltose, rather than glucose, fructose, or sucrose, in equimolarity (Blanc et al., 1999). Kinetic analyses were carried out on various physiological and biochemical indicators over the 8 weeks that the induction phase then expression of somatic embryogenesis can take. Embryogenesis induction in the presence of glucose, fructose or sucrose revealed strong callus growth in the first 3-4 weeks, associated with a high intra- and extracellular hexose content, a high starch content and a substantial decline in protein synthesis. In the presence of maltose, callus growth was slow and only half that seen with sucrose. This morphogenetic behaviour is associated with a drop in endogenous hexose and starch contents, and an increase in protein synthesis in the first three weeks of culture. The induction of embryogenesis in the presence of maltose was uniform and twice as fast as with sucrose supply. At the end of culture, peroxidase activity, antioxidant and membrane protein contents increased in these calluses; these characteristics may be associated with somatic embryo organization and with the maintenance of effective membrane integrity within a nutrient environment that has become limiting. These new results tally with data in the literature on the roles of sugars, and provide some precise information with regard to the 'carbohydrate deficit' hypothesis usually put forward to explain maltose action. An analysis of these results led to the hypothesis that regulation of endogenous hexose contents at a low level, through slow maltose hydrolysis, was a key element of the biochemical signal leading this callus towards somatic embryogenesis.

Thidiazuron required for efficient somatic embryogenesis from suspension-cultured cells ofPimpinella brachycarpa

To maintain embryogenic cell lines ofPimpinella brachycarpa, we suspension-cultured friable and rapidly growing yellowish calli in an MS liquid medium containing 0.2 ~ 2,4-D and 0.5pM BAP. Efficient somatic embryogenesis was achieved when selected cells were then transferred to an MS medium (0.2% gelrite) that contained 0.2gM 2,4-D, 0.5 uM BAP, and 10.0 laM TDZ (thidiazuron). These cells were cultured at 27°C under continuous illumination (21.5 I~E m-2 s-l). Embryogenic calli expanded about four-fold, and developed into pale yellow calli. Somatic embryogenesis was initiated only from glossy and nodular-type calli. After two more weeks of culture, globular embryos appeared on the surface of calli grown in the MS medium that contained 10.0 /aM TDZ only, or in combination with 0.5 gM NAA. Experimenting with 2,4-D, an auxin, to promote embryogenic calli resulted in excessive browning and death. We overcame this problem by growing glossy embryogenic and nodular calli on media that contained 10.0 gM TDZ. Calli that were not treated with TDZ turned dark brown and were not viable. Up to 74% of the calli showed somatic embryos when the medium was supplemented with 10.0 uM TDZ and 0.5 uM NAA. Embryos from these TDZ-induced, somatic embryogenic calli grew efficiently, forming multiple shoots and developing into normal plants. Therefore, efficient differentiation of suspension-cultured cell clusters into embryogenic calli, along with treatment of subsequent somatic embryos by TDZ, suggests that TDZ probably helps in establishing the optimum cytokinin-auxin ratio required for induction and expression of somatic embryogenesis.

Glycerol effects both carbohydrate metabolism and cytoskeletal rearrangements during the induction of somatic embryogenesis in chicory leaf tissues

In leaf tissue of the chicory hybrid ‘474’ ( Cichorium intybus L. var. sativum × Cichorium endivia L. var. latifolia), induction and expression of somatic embryogenesis can be separated into a two-step procedure by the presence of glycerol during the induction step. This effect of glycerol is caused by the inhibition of the initiation of the first divisions of the embryogenic cells by a so far unknown mechanism. In an attempt to unravel this mechanism, the effects of glycerol on carbohydrate metabolism and cytoskeletal rearrangements were studied. When the induction medium was supplemented with 〚 14C〛-glycerol for 24 h, about 25 % of 〚 14C〛-glycerol were converted to other soluble carbohydrates. Activity of glycerol kinase was very high during the induction phase of somatic embryogenesis and decreased after transfer. Glycerol supplementation was of no avail on glycerol 3-phosphate dehydrogenase activity. A nuclear magnetic resonance study showed that glycerol 3-phosphate had accumulated in leaf tissue. Microscopic studies using α- and β-tubulin antibodies revealed that cytoskeletal rearrangements were greatly affected by the presence of glycerol. Immunobloting using antibodies against α- and β-tubulins revealed that this effect of glycerol was not caused by alteration in the quantity of either type of tubulin monomers. We describe the progress made in the analysis of the effects of glycerol on somatic embryogenesis in chicory. New evidences are given on the occurrence of an active glycerol metabolism during the inhibitory treatment. Moreover, the effect of glycerol was correlated with a defect in the pre-mitosis cytoskeleton organization.

Regulation of in vitro somatic embryogenesis with emphasis on to the role of endogenous hormones

Different aspects of the in vitro somatic embryogenesis regulation are reviewed in this paper.work. A description of g General aspects, such as terminology, uses, stages of development and factors associated with the somatic embryogenesis, are described. is carried out. Although a brief description ofn the effects of the addition of different plant growth regulators to the culture medium wasis given, the article is centereds itself on the effect that the endogenous hormone concentrations in the initial explants and in the tissue cultures derived from them could play oin the induction and expression of somatic embryogenesis. It is significant that few to emphasize the low amount of systematic studies have been conducted, in this subject, in which different species and hormone groups were compared in cultures with and without embryogenic capacity. Moreover, the lack of correlation between the results presented in different studies the distinct works indicates that the hormone content of the cultures is not the only factor involved.

Carbon metabolism in in vitro cultures of date palm: the role of carboxylases (PEPC and RubisCO)

While describing major trends of carbon metabolism during the initiation and expression of somatic embryogenesis in date palm (Phoenix dactylifera L., cv. Deglet Nour), we have investigated the role of two carboxylases, namely PEPC (Phosphoenolpyruvate carboxylase, EC 4.1.1.31) and RubisCO (Ribulose 1,5-bisphosphate carboxylase/oxygenase, EC 4.1.1.39), in embryogenic and non-embryogenic cultures. The detection of PEPC activity on polyacrylamide native gels after electrophoresis revealed the presence of 3 active isoforms in crude extracts from the embryogenic (E) callus strain, whereas only a single band was present in the non-embryogenic (NE) one. The level of PEPC specific capacity was of the same order (3.9 ± 1.2 μmol CO2 h−1 mg−1 TSP) in both types of cultures. Further changes in carboxylase (PEPC and RubisCO) activities during the growth and development of somatic embryo–derived plantlets were also analysed. The PEPC/RubisCO ratio was found to progressively decrease (from 17.7 to 0.2) throughout the in vitro development of plantlets, due to a substantial depletion of PEPC activity, which decreased from 5.3 to 1.2 μmol CO2 h−1 mg−1 TSP. Concomitantly, RubisCO assumed greater importance (from 0.3 to 5.3 μmol CO2 h−1 mg−1 TSP ) and became the main route for inorganic carbon fixation. Western blot analysis using polyclonal antibodies raised against PEPC and RubisCO purified from tobacco leaves confirmed this trend in terms of relative enzyme abundance.

Relations between exogenous growth regulators and endogenous indole-3-acetic acid and abscisic acid in the expression of somatic embryogenesis in Hevea brasiliensis (Müll. Arg.)

Endogenous IAA (indole-3-acetic acid) and ABA contents were measured during the somatic embryogenesis process from Hevea brasiliensis (Müll. Arg.) callus. The decrease in 3,4-D (3,4-dichlorophenoxyacetic acid) and BAP (6-benzylaminopurine) supply in the culture medium and the addition of ABA both stimulated embryogenic induction. But only exogenous ABA sustained embryogenic expression of the callus. The two operations resulted in a decrease in endogenous ABA and an increase in IAA in callus. Low endogenous ABA levels (2–4 nmol/g dry wt.) appear to be necessary for the acquisition and conservation of a embryogenic state. Non-embryogenic calli accumulated high levels of ABA (25–40 pmol/g dry wt.). This accumulation confirm the hypothesis that non-embryogenic Hevea calli were water stressed.

Modulation of somatic embryogenesis in early and late-stage embryos of wheat (Triticum aestivum L.) under the influence of (�)-abscisic acid and its analogs

Zygotic embryos from ten spring wheat (Triticum aestivum L.) genotypes were tested for embryogenic callus induction in the presence or absence of externally supplied (±)-abscisic acid (ABA) and two of its analogs, methyl abscisate and methyl epoxy-beta-ionylideneacetate. (±)-ABA and its analogs suppressed precocious germination of cultured late-stage embryos and promoted embryogenic callus induction. A significantly greater number of plants was regenerated from calli induced in the presence of ABA and ABA analogs. Early-stage embryos when cultured in the presence of (±)-ABA showed a negative response. Possible roles of ABA with respect to the expression of somatic embryogenesis are discussed.