Secondary metabolism in cell cultures

Secondary Metabolism in Cell Cultures of Some Terpenoid-Indole Alkaloid Producing Plants... 

In the subsequent paragraphs some of the work in our laboratories in this field will be reviewed. It particularly involves the secondary metabolism in cell cultures of plants capable of producing terpenoid-indole and related alkaloids, i.e. Cinchona and Tabernaemontana. 

P. R. H. Moreno, Influence of stress factors on the secondary metabolism in suspension cultured Catharanthus roseus cells. Ph.D. Thesis, Leiden University, 1994. 

In the interdisciplinary field of biophysics and biotechnology, the bioeffects of electric field have received considerable interest for both fundamental studies on these interaction mechanisms and potential application. However, the effects of pulsed electric field (PEF) on secondary metabolism in plant cell cultures and fermentation processes have been unknown. Therefore, it would be very interesting to find out whether PEF could be used as a new tool for stimulating secondary metabolism in plant cell cultures for potential application to the value-added plant-specific secondary metabolite production. Furthermore, if the PEF permeabilization and elicitation are discovered in a cell culture system, the combination of... 

Girod, R-A. and Zryd, J.-R, Secondary metabolism in cultured red beet Beta vulgaris L.) cells Differential regulation of betaxanthin and betacyanin biosynthesis. Plant Cell Tiss. Org. Cult., 25, 1, 1991. 

Yeoman, M. M. and Yeoman, C. L. 1996. Tansley review no 90 - Manipulating secondary metabolism in cultured plant cells. New Phytologist, 134(4) 553-569. 

Kurz, W. G. W. and Constabel, F. 1985. Aspects affecting biosynthesis and biotransformation of secondary metabolities in plant cell cultures. CRC Critical Reviews in Biotechnology, 2(2) 105-118. 

N. J. 1989. Regulation of secondary metabolism in transformed root cultures. In Primary and Secondary Metabolism of Plant Cell Cultures II (Kurz, W. G. W ed.), pp. 58-72. Berlin Springer-Verlag. 

Cell line selection is one of the traditional and effective approaches to enhancing metabolite accumulation, and biochemical studies provide the fundamental information for the intentional regulation of secondary metabolism in plant cells. In a carrot suspension culture regulated by 2,4-dichlorophenoxyace-tic acid, Ozeki et al. [7] found that there was a correlation between anthocyanin synthesis and morphological differentiation for somatic embryogenesis they also demonstrated the induction and repression of phenylalanine ammonia lyase (PAL) and chalcone synthase correlated with formation of the respective mRNAs. Two biosynthetic enzymes, i. e., PAL and 3-hydroxymethylglutaryl-CoA reductase, were also related with shikonin formation in Lithospermum erythro-rhizon cultures [8]. 

Morris P, Scragg AH, Stafford A, Fowler MW (eds) (1986) Secondary metabolism in plant cell cultures. Cambridge University Press, Cambridge... 

Fett-Neto AG, DiCosmo F (1996) Production of paditaxel and related taxoids in cell cultures of Taxus cuspidata perspectives for industrial application. In DiCosmo F, Misawa M (eds), Plant cell culture secondary metabolism toward industrial application. CRC Press, Boca Raton, p 139... 

Morris, P. Scragg, A.H. Stafford, A. Fowler, M.W. Secondary Metabolism in Plant Cell Cultures. Cambridge University Press, Cambridge, 1986. 

Treatment of cell suspension cultures of T. rugosum with a yeast glucan elicitor induced the production of tyrosine decarboxylase in the late exponential and early stationary growth phases of the cells. Tyrosine decarboxylase has been suggested as the key enzyme between primary and secondary metabolism in the biosynthesis of norlaudanosoline-derived alkaloids, and a good correlation between induced tyrosine decarboxylase activity and berberine biosynthesis has been established [163]. 

For C. roseus suspension-cultured cells, elicitation with fungal elicitors results in the induction of TDC activity (99,186,202,203,284,329-331). This is due to the induction of expression of the Tdc gene. Similarly, SSS activity is induced (202,203,284,329,330). The induction by the Pythium aphanider-matum or yeast elicitor of the transcription of both genes is not affected by cycloheximide that is, the induction is independent of de novo protein biosynthesis, and thus follows an already available signal-transduction chain. The response is quite fast, for the enhanced transcription can already be measured 15 min after elicitation (202,203). Also, the NADPH cytochrome P-450 reductase mRNA level is induced by elicitation with fungal elicitors (113). Moreno et al (99,151) measured activities of a number of enzymes involved in secondary metabolism in C. roseus before and after elicitation with a P. aphanidermatum preparation. GlOH activity was found to be slightly decreased by elicitation and IPP-isomerase showed similar behavior. The pattern of terpenoids formed by the crude enzyme extracts from elicited and nonelicited cells was different. The total incorporation decreased, that is, the activities of the enzymes of the terpenoid pathway were lower. The relative incorporation decreased particularly for squalene. 

The various strategies followed to obtain high producing cell lines will be briefly discussed separately (see Section II). The economics of a plant cell culture production process are discussed below (see Section III). For cell lines that do not produce, it will be necessary to learn more about the regulation of secondary metabolism in order to eventually be able to use genetic engineering for improving production (see below). 

Why the cells are capable of expressing the anthraquinone biosynthesis in in-vitro cell suspension cultures and not the alkaloid biosynthesis has still to be answered. Further studies on the genetic regulation of the secondary metabolism in Cinchona are needed to answer this question and to eventually open the way for a biotechnological production method. 

Inorganic metal salts can induce secondary metabolism in plant cell cultures, such as Cu and Ag. Cu elicited phytoalexin production in rice plants. Adding AgNOs induced taxol biosynthesis. Rare earth metal salts, such as (NH4)2Ce(N03)6, can also increase the accumulation of paclitaxel in Taxus cells. Ginsenoside biosynthesis was elicited in cell cultures of Panax ginseng by vanadate. The metabolic action of inorganic metal salts inducing the accumulation of secondary metabolites may be similar to other natural chemical elicitors. ... 

Numerous studies of secondary metabolism in plant cell cultures have been reported but few have mentioned alkane accumulation, although probably it is widespread. The alkane pattern in cell suspensions of Euphorbia species was similar to that in leaves (mainly n-C2s, 29 alkanes) and recoveries were 5 to 60% (in different cell lines) of that obtained from the parent tissue , and similar products (n-C29, n-C3i predominant) were obtained for cultures of guayule . In contrast, cell lines from Pogostemon species yielded alkanes (n-C g and n-C v) of lower chain length than the major (n-C3i) alkane of the cutin of the parent at levels only ca 10% that in the latter . Callus from a Rosmarinus species similarly yielded n-C g, n-Cj and n-Ci7 whereas the parent leaf tissue mainly accumulated a n-C29 alkane . ... 

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