The flora of Primorye is a highly rich potential source of traditional
and novel medications of plant origin. With regard to the number of unique
medicinal plants, either totally unknown or little known in Russia, but
widely used overseas, Primorye is unequalled in Russia. And yet, as a rule,
those plants are represented by rare or disappearing species, and this
does not allow using them widely in medicine. This also fully concerns
the relict Far Eastern plant, ginseng (Panax ginseng C. A. Mey).
Ginsenosides were found to be ginsengТs biologically active substances, with which its remedial properties are chiefly associated (Tanaka and Kasai, 1984). Ginsenosides were proven to produce a strong immunlostimulative, radioprotective, antitumoral, anti-inflammatory, and anti-ulcer effect. They also suppress development of thrombi, normalize blood pressure, increase the life of brain cortex neurons, and positively affect the endocrine system and carbohydrate metabolism. The use of ginseng preparations enhances work efficiency and retards aging. Nevertheless, the use of ginseng in medicine is restricted by low reserves of the natural plant. Studies performed in recent years have established that genetic resources of wild ginseng are almost exhausted (Zhuravlev et al., 1996).
The shortage of natural raw material
could be overcome by introducing plant cells into culture in vitro, i.e.
into the culture of cells growing outside the organism on specially selected
nutrition media. Introduction into cell culture of valuable and rare plants
would at the same time resolve two tasks: first, it would create a renewable
source of raw material for manufacturing the medicinal preparation and,
second, create prerequisites for retaining the plant gene pool. Therefore,
for over thirty years now we have conducted work to create a reproducible
biotechnological source of ginsenosides by obtaining ginseng cell cultures
that would synthesize a set of ginsenosides in amounts and correlation
close to those in the native plant. At the same time, most of the obtained
ginseng cell cultures differ from natural roots in that they do not contain
the entire set of ginsenosides, have lesser ginsenoside total content and
different correlation of individual ginsenosides. At present, there are
several techniques aimed at activating synthesis of biologically active
substances in in vitro cultures.
Researchers (Zhuravlev et al.,1990; Bulgakov et al., 1991) from the Institute of Biology and Soil Science, Far East Branch, Russian Academy of Sciences, have obtained from various ginseng plant organs cell cultures capable of synthesizing ginsenosides. In 1992-1997, we for the first time performed a comparative study of the efficacy of various pathways in regulating ginsenoside synthesis in obtained cultures. We succeeded in increasing the yield of ginseng biologically active substances by using selection, light cultivation regime, biosynthetic ginsenoside precursors (mevalonic acid and farnesol) and specific phytohormones. We also developed a scheme of combined regulation of ginsenoside synthesis by altering cultivation conditions and media composition in combination with genetic engineering. For the first time, we performed work aimed at obtaining ginseng cell cultures containing alien genes and to search for the gene responsible for increased ginsenoside synthesis. The use of genetic engineering methods allowed obtaining a number of highly productive transgene ginseng root cultures capable of stably synthesizing target substances during lengthy cultivation to make these cultures a novel promising source for manufacturing biologically active substances. Using gene transformation of rolC genomes from Agrobacterium rhizogenes, we for the first time succeeded in inducing morphogenesis (forming of shoots and leaves ginseng cell culture, 1c. Shoots and leaves of the morphogene culture were found to synthesize ginsenosides in amounts and correlations inherent in plantation plant overhead portion.
M. KHODAKOVSKAYA, Cand. Sci. (Biology), Senior Researcher, Laboratory of Biotechnology, Institute of Biology and Soil Science, F. E. Branch, Russian Academy of Sciences.
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