Plant cell cultures chloroplasts

Economically more meaningful would be the ab initio-synthesis of complex natural compounds by plant cells from CO2 and light. For this purpose the chlorophyll containing green parts (chloroplasts) of the plants would be needed which are able to effect photosynthesis. Only laboratory results are available in this area. More advanced results about flavour generation in plant cell cultures are available for ... 

Plant cell culture techniques have provided the tools to enable successful recovery of chloroplast recombinants. These include utilization of selectable chloroplast markers such as resistance to the emtibiotics streptomycin and lincomycln (10) and efficient methods for somatic cell fusion that enable the production of large numbers of cells with mixed chloroplast populations (33). 

All these factors are important for the development of plant cell cultures. For example, cultures of Lupinus polyphyllus only synthesize alkaloids when kept in the light and alkaloid content is correlated with chlorophyll content. This may be explained by a better supply of lysine (formed in the chloroplasts), the fact that the enzymes of alkaloid biosynthesis have a pH optimum of about pH 8, which is created in the chloroplast stroma only in the light, and that the enzymes are subject to activation by reduced thioredoxin which is generated only in the light (Wink, 1987). The alkaloids of Peganum harmala, which are formed in the roots of the plant, act in an opposing manner. Cultures maintained in the light fail to produce the alkaloids, whereas those kept in the dark synthesize harman alkaloids (Barz and Hiisemann,... 

In vitro tissue and cell cultures of lupin plants are not appropriate systems for the study of biosynthesis of lupin alkaloids, because the production ability by in vitro culture is rather low, i.e., 10 2 to lO times compared with that of differentiated plants. The production of the alkaloids of lupinine- and sparteine-groups by cell culture have been reported by us [59] and by Wink s group [60]. We have also successfully produced matrine in green callus culture and in multiple shoots of Sophora flavescens [61]. The producibility of matrine was positively correlated with the chloroplast formation. This indicates that the formation of carbon skeleton of matrine-type alkaloids also likely takes place in chloroplasts in plant cells as postulated in that of sparteine-type alkaloids [62]. 

Cell Culture Approaches for Obtaining Herbicide-Resistant Chloroplasts in Crop Plants... 

Genetic techniques for obtaining chloroplast-encoded herbicide resistance in crop plants are reviewed. These are based on the use of cell culture methods and Include mutant selection in cultured cells, chloroplast transfer via protoplast fusion, and genetic recombination between chloroplast genomes. The first two methods are described in detail using trlazine resistance as an example. 

In a plant cell the redox reactions involved in the photosynthetic assimilation of CO 2 and nitrate are located in four different compartments the chloroplast stroma, the mitochondrial matrix, the peroxisomal compartment and the cytosol. The present report deals with the question in which way redox equivalents can be transferred between these different compartments and how the redox processes in the various compartments can be coordinated. The experiments shown in the following have all been carried out with spinach leaves grown in hydroponic culture in a 9 h light 15 h dark cycle. 

With respect to fatty acid biosynthesis, plant cell suspension cultures resemble cells in green leaves of intact plants. In leaves of Flacourtiaceae, straight-chain and cyclic fatty acid biosynthesis is located in chloroplasts. The locus of this biosynthetic process in seeds, the main cyclopentenyl fatty acid-producing organ, is not known the results obtained with cultured cells may indicate localization in the cytosol. However, the model function of cell cultures should be considered with caution. 

Little is known about plant PAP. It has recently been characterised in microspore-derived cell cultures [6] and in spinach chloroplasts [7]. The biological properties of CHAPS-solubilised PAP were investigated and some of these are presented in Table 1. 

Feeding experiments using total plants revealed that phylloquinone is formed in leaves from shikimate /20/ and 2-succinylbenzoate /21/. Just recently Leistner s group provided evidence from studies on E. coli /22/ that isochorismate and not chorismate reacts with 2-oxoglutarate to form 2-succinylbenzoate. The results from studies on cell cultures /23,24/ and chloroplasts /25,26/ are summarized in Fig. 5. The chloroplast envelope is the site of prenylation /25/ and the thylakoid membrane of methylation reaction /26/, however, compartmentation of the other reactions remains still unclear. The synthesis in plants resembles the microbial one /27/ though phytyl-PP is preferred as prenyl donor in plants /25/. 

C- plants (9). One of the features of C. plants, is the presence of "Kranz" anatomy. There is compartmentalization of enzymes in "Kranz" anatomy viz PEPC in the cytosol of mesophyll cells and RuBISCO in the chloroplasts of the bundle sheath cells(ll). Accordingly in the present study, predominent activity of PEPC in the partially green maize callus cultures and lowest portion of young leaf lacking well developed chloroplasts can be explained. 

Quinolizidine alkaloids are derived from lysine. Studies with labeled precursors indicate that a symmetrical intermediate, cadaverine (20), is involved in their formation (Herbert, 1988 Kinghom and Balandrin, 1984 Leete, 1983 Spenser, 1985), although no intermediate comparable to the dimeric form plays a role in the formation of pyrrolizidine alkaloids is involved (Spenser, 1985). Much recent information is based on cell suspension cultures of Lupinus polyphyllus, Baptisia australis, and Sarothamnus scoparius (all Faba-ceae). Lysine decarboxylase is localized in leaf chloroplasts (Wink 1987 Wink and Hartmann, 1982,1984) the presence of a diamine oxidase does not appear to be involved. Lysine decarboxylase is found in all parts of Lupinus plants. 

This suspension culture of Morinda cells is being studied because the biosynthesis of anthraquinones and its glycosides can be triggered in the culture. Upon transfer of cells into darkness and a medium containing sucrose the chlorophyll decreases and the lipoquinones (including phylloquinone) disappear from the cells (Table 1). Simultaneously, anthraquinone pigments are formed (Fig. 4) and the cultured cells turn yellow and eventually red. Thus, in the suspension culture photoautotrophy correlates with lipoquinone synthesis while heterotrophy correlates with anthraquinone synthesis. This reflects the situation in the intact plants where lipoquinones are associated with chloroplast whereas anthraquinones occur in the roots. 

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