Download Plants as source of biologically active substances

Plants as source of biologically active substances
Plants are producers of many BAS – substances, capable to affect on
biological processes in an organism. For ex., glycosides, saponins, sterols,
carothenoids, polyphenols, alkaloids, vitamins, quinones, and also the substances
possessing specific aroma, taste and coloring. Biologically active agents are
products of a secondary methabolism which are called biosynthesis by-products.
Now it is known more than 100 000 secondary metabolites produced by plants.
Many of them are practically, economically important products and are used in the
pharmacological, cosmetic, food industry.
Plant product
Plant species
Codein (alcaloid)
Papaver somniferum
Diosgenin (steroid)
Dioscorea deltoidea
Quinin (alcaloid)
Cinchona ledgeriana
Digoxin (cardiosteroid)
Digitalias lanata
Scopolamin (alcaloid)
Datura stramonium
Vincristin (alcaloid)
Catharanthus roseus
Cell engineering of plants is considering
various ways to get cell culture, cultivation of plant
and animal cells, the selection of isolated protoplasts,
biological engineering, and the creation of
experimental systems association between cultured
cells of higher plants and microorganisms.
Cell technologies, based on in vitro cultivation
of organs, tissues, cells and isolated protoplasts of
higher plants, can facilitate and speed up the
traditional breeding process. This, above all, the
following technologies: the culture of ovules and
embryos, the regeneration of plants from tissue lethal
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hybrids, experimental haploids, cryopreservation of the gene pool, clonal
micropropagation. Cell Engineering offers new ways for developing high plant
shapes. This hybridization of somatic cell transfer of foreign genes.
Ten most used medicinal substances, received from plants
API
Steroids
from diosgenin
Action
Contraceptive
Source plant
Dioscorea deltoidea
Codein
Pain-killer
Papaver somniferum
Atropin
Anticholinergic
Atropa belladonna L.
Reserpin
Hipotensive
Rauwolfia serpentina L.
Hyosciamin
Anticholinergic
Hyoscyamus niger L.
Digoxin
Cardiac
stimulant
Digitalis lanata L.
Scopolamin
Anticholinergic
Datura metel L.
Digitoxin
Cardio-vascular
Digitalis purpurea L.
Pilocarpin
Cholinergic
Pilocarpus jabonandi
Chinidin
Antimalarial
Cinchona ledgeriana
Examples of medicinal substances received on a basis of callus cultures
Steviozid is natural sweetener and sugar substitute, is successfully used
instead of artificial sweetening substances. Initial plant is Stevia rebaudiana
Bertoni.
Arglabin is antineoplastic substance. Initial plant is Artemisia glabella Kar.
et Kir. Is a part of the preparation of the same name.
Lappakonitin is diterpen alkaloid, antiaritmic. Initial plant is Aconitum
septentrionale Koelle. Is a part of Allapinin's preparation
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Genetic engineering of plants is not as well developed as in the case of
animals and microbial cells. However, it is now attracting more and more
attention, because it opens new opportunities in agriculture. The usual selection is
a slow process and, in addition, it is limited by natural species barrier. The
introduction of new genes using recombinat DNA technology could accelerate this
process and to significantly expand its capabilities. Besides plants have significant
feature - the whole plant can be grown from a single cell. This does not apply to all
plants. For example, cells of cereals or legumes rarely undergo such
redifferenciation, while the cells of tobacco, tomato or carrot, as shown, are
redifferenciation relatively easy.
When dissolving the cellulose of plant cell wall enzymes by celulases,
protoplasts are formed. They can easily penetrate macromolecules, including
DNA. Two different cells as protoplasts connected with the formation of protoplast
fusion - somatic hybrid cells. Protoplasts are able to restore the cell wall and then
give the whole plant. The plant can be obtained from protoplasts that have
incorporated foreign DNA or hybrid protoplasts.
If there are methods of introduction into plant cells of certain genes that are
capable of functioning and stable inheritance, offers real opportunities to create
plants with pre useful properties. Vectors to introduce genes into plant cells can be
based on the replicons of plant viruses. However, to date, attempts to obtain such
vectors satisfying, in particular the requirement of stable inheritance, were not very
successful.
Created transgenic canola containing the genes of individual human
neuropeptides such as Leu-enkephalin gene-related albumin rapeseed. With one
hectare of land sown with rape so, you can receive up to 3 kg of neuropeptide.
A new variety of tomatoes, long lasting without softening due to the
suppression of activity of the enzyme polihalacturonidase.
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Such genetically engineered soybean varieties that are resistant to insects,
herbicides, viruses, and produce more storage protein-enriched methionine was
designed.
Based on the methods of genomic engineering obtained interspecific hybrids
of cabbage, potatoes and tobacco with turnips, potatoes with tomato - "Pomat"
tomato wild species that is resistant to some viruses, and cultural variety.
The world's first genetically engineering a chimeric plant "sanbin" received
in the U.S. as a result of gene transfer bean storage protein gene in fazeolina
sunflower. In 1984-87. Transgenic plants: tobacco, tomato, celery, alfalfa and
cotton. The introduction of transgenic wheat genes that determine animal proteins
(myosin) can bring bread to the quality of animal products.
Introduction into a plant gene encoding the protein thaumatin (600 times
sweeter than glucose), can improve the taste of many fruits, without increasing the
carbohydrate content.
In the United States are grown transgenic rapeseed, soybean, cotton, and
herbicide-resistant, created transgenic tomatoes containing genes of tobacco
mosaic virus, which makes them resistant to other viruses.
Genetic engineering methods are introduced into the plant genome, genes
encoding proteins that are toxic to many insects. So are plant varieties that are
resistant to pests. Genetic engineering solves the problem of artificial food.
Already, the bacteria enter the genes that control the synthesis of amino acids, the
problem is a strain of yeast, bacteria that produce food proteins, and they are
intended to cultivate sugar industry waste.
Transgenic (or genetically modified) is a plant in which the gene by genetic
engineering transferred genes (called "transgenic") from other organisms. Transfer
process is called genetic transformation. The main advantages of this technology
compared to conventional breeding are: the possibility of transfer of a single gene,
which is practically not affect the original genotype, the ability to make the signs
that can’t be transferred by mating with closely related species, and a significant
acceleration of the acceleration of new genotypes.
The most widely used method of transformation - Agrobacterium has been
developed based on the natural process. The soil bacterium Agrobacterium
tumefaciens to infect dicotyledonous plants, causing the tumor - the Gaulsspreader. As it turned out, and there are transfer and integration into the plant
genome of two groups of genes: some products interfere with the normal
metabolism of plants and contribute to the widening of the tumor, and other
products synthesized opin substances unwanted plants, but are used as food by
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bacteria. Scientists modified Agrobacterium so that they are instead transferred to a
plant's own genes to the right person.
Subsequently, a number of other methods of transforming plant cells, of
which the most widely purchased bioballistic. It is used most often for genetic
modification of monocots are unaffected by Agrobacterium. In special installations
of gold or tungsten microparticles coated with DNA are accelerated by compressed
gel, and they penetrate the target cell DNA.
Symptoms, which may give them with the help of genetic engineering, are
very diverse and mostly limited to the presence of the corresponding genes.
Roughly speaking, they can be divided into three groups.
The first is the features and interesting producers: resistance to various
environmental factors - herbicides, diseases, pests, drought, salinity, improved
mineral nutrition, rooting.
The second group of features of interest directly to consumers - the
modification of flavor and aroma of fruit, longer storage, change in color of
flowers, seedlessness, improving the nutritional value of plants.
The third group includes plants' biofactories "capable of synthesizing
vaccines, enzymes, biopolymers and other useful substances.
Cell Engineering produces varieties of plants under controlled conditions, as
well as pharmaceutical preparations (ubiquinone-10-tobacco-yatrorrizin barberry,
shikonin- lithospermum).
Callus culture is disorganized proliferative tissue, consisting of
differentiated cells. Callus (means corn) may be formed as isolated pieces of tissue
explants, and the whole plant in the defeat. Callus tissue is amorphous and has no
anatomical structure, and can be of different consistencies:
1. loose, consisting of strongly cell hydration, easily divided into separate
loose agregates;
2. medium density with well-defined individual meristematic centers;
3. thick, in which the elements are differentiated cambium and conducting
system.
Obligatory condition of tissue dedifferentiation and turning it into callus is
the presence in the medium of phytohormones: auxin and cytokinin. Auxins
promote differentiation, and cytokinins cause proliferation.
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Tumor cells, in contrast to the callus can grow on nutrient media lacking
phytohormones (auxin, IAA, etc.). They cannot form normally organized
vegetative organs. And in some cases, of which there may be ugly organ-like
structure, so they cannot be applied breeding.
Bacterial DNA exists not only in the form of chromosomes, but in the form
of small circular molecules (plasmids). Bacterium Agrobacterium tumefaciens
plasmids contain among others, causing tumors (Ti-plasmid). On this plasmid
among other genes have an area of T-DNA containing the genes for tumor
formation in plants and opine synthesis. It is this piece of Agrobacterium plasmid
DNA inserted into plants. It turned out that, in principle, Agrobacterium can
survive in any plant DNA, which is located at the site of plasmid. Therefore, in the
plasmids used in genetic engineering purposes, natural substitute for any other
genes of interest to the person. Typically, it is two to three genes: the target,
which gives, for example, resistance to insects, selective, which confers resistance
to certain substances (most often - antibiotics), which allows transformed cells to
grow in a culture medium with antibiotics, while non-transformed cells in it are
dying, and sometimes a reporter gene, which can qualitatively determine the
transformed cells, such as painting or glow in ultraviolet light.
Plant regeneration from callus based on totipotent. This phenomenon was
discovered in the Gaberland’s laboratory. Totipotency - a property of somatic cells
of plants fully realize its potential for the formation of the whole organism. Its
essence is that if a plant cell is isolated, it behaves like the cells of the embryo sac
that is formed embrioid and whole plant.
Totipotency of cultured cells suggests that genetic information is stored. But
its implementation requires specific conditions. Among the factors that could
completely or at least partially restore the masked genetic information, are light,
growth regulators, precursors and batteries. The stimulating effect of light on the
formation of secondary compounds have been shown by the example of
carotenoids, essential oils. Additionally important is the temperature, humidity,
light and periodically update the medium, since the growth of the cells it
accumulates metabolites that adversely affects the crop. therefore, this technique is
associated with changes, i. e. with the transfer of part of the biomass to the new
environment in another vessel ("passages"). When cultured plant cells have a low
rate of reproduction than microbiological objects, so the duration of cultivation
determined not tens of hours and tens of days.
Method for growing cells in vitro is that the plant, isolated from any plant
organ tissue (explant) is placed on the culture medium, the components of which
are chosen so that they support the normal functioning of cells and stimulate the
division. Therefore, these cells can be cultivated only in complex nutrient media
containing salts of nitrogen. K, Mg, P and a number of trace elements, organic
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substances - carbohydrates, amino acids, vitamins, hormones (kinetin, indoleacetic
acid).
Callus cells have different shapes. When callus in the membranes increases
the content of saturated fatty acids, unsaturated and disappear, there is a process of
differentiation, i. e. transition of cells to the level of the isolated cells.
Callus can be obtained from a number of plant tissues. Young cells are more
suitable for this purpose than mature, this is especially noticeable on the leaves.
Pieces of the stem of trees is bad material for callus. Any type of plant callus
provides, subject to certain methodological techniques of cultivation.
In the cells of explants, consisting of specialized cells dividing at the
beginning of cultivation can be observed changes in metabolism associated with
traumatic synthesis, with dedifferentiation and prepare for the process of division.
It can be assumed that the injury results in the release of cell biologically active
substances - inducers of cell division, different in nature from the known growth
factors (auxins, gibberellins).
Clonal micropropagation is the use of in vitro techniques for rapid
propagation of plants, identical to the original, asexually. The term "clone" (from
the Greek - the son) was proposed Weber in 1903 in the study of vegetative
propagation of plants.
Clone is a collection of cells or individuals descended from a common
ancestor by asexual reproduction - the basic unit of account in the genetics of
microorganisms. At the heart of the formation of clones is mitosis, so it is believed
that the clone is made from genetically homogeneous cells. However, this is very
concerning because of spontaneous mutations. Only cloning can save particular
grade. Clonal micropropagation is the way to obtain clones of plants by growing
them from a single cell by totipotent cell culture. Clonal reproduction has many
advantages and is very promising:
1. Clonal reproduction ratio is much higher than the usual methods of
reproduction. So, from one plant gerbera a year you can get 50-100 plants in the
usual way, in clonal propagation of tissue culture to 1 million
2. Plants can be propagated throughout the year.
3. Thousands of plants can grow in a relatively small area of the laboratory.
4. Along with breeding and improvement of plants are (from viruses and
pathogens).
5. Clonal propagation method are planting plants that reproduce sexually
slowly or not at all propagated vegetatively.
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6. In clonal reproduction, as opposed to sexual reproduction, the offspring
are genetically homogeneous. There are 2 types of clonal propagation:
1) small-scale (with selection works);
2) mass-clonal, commercial reproduction;
a) the release of virus (potato);
b) obtaining planting material (flowers, crops).
When used as explants differentiated plant tissues may cause mutant forms.
All manipulations in clonal micropropagation of plants carried out under aseptic
conditions, that is in compliance with the microbiological technique works. Work
is carried out or in microbiological boxes irradiated with UV light, or in a laminar
box, where asepsis is achieved applying sterile air.
The whole process of clonal micropropagation has a duration of about three
months, and it can be divided into 4 stages.
At the first stage, the choice of the donor plant, isolation and sterilization of
explant and creating conditions for the formation of callus on solid medium.
The second stage is associated with an increase in the number of initials on
the callus formation and shoot.
The third stage - the test-tube rooting propagated plants and their adaptation
to the conditions in vitro.
Fourth stage - growing plants taken from test tubes in a greenhouse and
hardening before planting in the field.
One of the major problems with the multiplication of the callus is a
reduction in the callus growth.
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Getting plants through organogenesis can be done in 3 ways:
1. By forming adventitious of callus derived from explants.
2. Through the formation of adventitious organs directly from explants
without an intervening callus phase.
3. Through the formation of regenerated plants from shoots formed from the
swollen buds.
The main disadvantages of clonal micropropagation of plants:
1. Most of the complexity and high cost. The need to automate and radically
new techniques. These include the failure of rooting plants in vitro and
involvement of hydro-and aeroponics. Further progress will be linked to the
automation and robotization of time-consuming procedures.
2. All specimens of this species occur from a single meristem and have
reduced genetic diversity. Therefore, new diseases can be catastrophic for them by
the same susceptibility to pathogens.
Therefore, along with the development of vegetative propagation technique
based on the culture of meristematic cells and is necessary to have a collection of
seeds for conservation of genotypes necessary to maintain genetic diversity.
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Cultivation of protoplasts
Protoplast culture methods are consistent with those used for cell cultivation.
Protoplasts were plated as a liquid and on solid medium of the same composition
with different concentrations of agar.
The main requirement for used means is that in the process of cultivation is
no destruction of protoplasts and the environment was optimal for the formation of
cell colonies. As long as the protoplasts did not form a cell wall, they are a very
delicate structure and work with them should be carried out under mild conditions.
The conditions in which the protoplasts are cultivated, mainly corresponding
to those used for the cultivation of plant cells in culture. The content of mineral
salts may change somewhat. As a rule, the medium should consist of physical
stabilizer, inorganic compounds, carbon sources, vitamins, organic nitrogen
sources and phytohormones.
Mannitol, sorbitol, and their combination can be used as an osmotic
stabilizer. The basis is the composition of mineral salts in the culture media of
plant cells. You can change the ratio of ammonium and nitrate nitrogen, depending
on the needs in their cells, increase the concentration of CaCl 2 to stabilize the
resulting cell wall. Once formed and began to share cells, they can be placed in
culture conditions usually used for plant cells.
In the first days of cultivation a number protoplatov dies, which may be due
to the heterogeneity of the population with respect to the action of osmolitikov.
The remaining protoplasts within hours start to synthesize cell wall. This process is
fully completed when the right conditions of isolation and culturing for 1-4 hours.
In this case, the protoplasts lose spherical, elongated cells. The rate of regeneration
of the cell wall depends on the plant species and tissues from which derived
protoplasts, as well as on the degree of differentiation. Under adverse conditions,
the isolation and culture of protoplasts cell walls are not formed on the entire
surface. At the break out part of the protoplasm, being surrounded by the plasma
membrane. It may be in the vacuole. This so-called kidney. "Budding" comes at an
elevated concentration of osmotically active substances in the presence of
unsuitable for the crop of sugar, with a low content of CaCl2, etc.
When the right conditions for the isolation and cultivation of the third and
fourth days after sowing observe the first division of the protoplasts. In most cases,
then formed multicellular aggregates, developing later in the callus, which can
regenerate the whole plant. Plant regenerates from protoplasts prepared now for
alfalfa, tobacco, carrots, tomatoes and many other agriculturally important plants.
Prospects of drugs based on plant cells
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Advantages of a number of pharmacological agents from plants is as
follows:
• independence from climatic, seasonal and geographical conditions;
• stability of output during the year;
• reduction of the area of the soil involved in the economy.
At the base of cell culture you can:
• receive certain substances inherent in certain plants, such as nicotine,
codeine, quinine, saponins, etc.;
• to ensure the synthesis of new products difficult to grow plants such as
ginseng adaptogen out;
• receive a new substance;
• use of cells for biotransformation of the final product.
Currently, there are industrial production of several valuable compounds
from plant biomass by in vitro. Well established in Japan, the release of such
drugs: shikoin (vorobeynika of pharmacy), ubiquinone (from tobacco, digoxin
(digitalis of woolly), diosgenin (Dioscorea deltoid).
Industrial production of drugs on the basis of cultures, cells guarantee a good
yield. This can be confirmed by comparing the output percent of the active
ingredient of solid biomass feedstock taken in an equivalent amount. For example,
preparation of anthraquinones from Cassia:
• Biomass - 0.334% 0.209% whole plant dry weight;
• diosgenin - a tuber, 26 mg per 1 g of dry weight, biomass - 26 g per 1 g of
dry weight.
In the 60's proved the ability of cells and tissues of plants to grow, divide,
organoobrazovaniyu and secondary metabolism, ie the ability of any cell to form a
complete plant, as genetic and physiological capacity for secondary metabolites
present in every cell.
For crops needed highly plant cell. Since the growth of Rhodiola rosea more
promising are cells of root system.
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For growth and synthesis of products of secondary metabolism requires the
selection of ingredients of the culture medium, which is carried out in two
directions and evaluate:
- The impact of environment on the formation of biomass;
- The impact of the environment on the synthesis of secondary products.
The components of the growth medium plant cell cultures should include:
basic inorganic nutrients, sources of iron, organic supplements (vitamins, growth
regulators), a carbon source, as described above.
There are several standard culture media, widely used in cultivation, but the
amount of growth regulators in them varies depending on the type of plant. the
yield can affect the concentration of the carbon source, and the other components
of the environment. So in cell culture vinca alkaloids increased output was due to
the increase in the concentration of sucrose in the medium, and the culture of carrot
cells accumulate anthocyanins stabilized, when used as a limiting factor of the
phosphate.
As regulators of growth and synthesis of products of secondary metabolism
using auxins, including indole-3-acetic acid, naphthylacetic acid, 2,4dichlorophenoxyacetic acid, and tsitohininy. The synthesis of secondary
metabolites affect introduced into the medium quadrupeds predecessors, which can
stimulate certain enzymatic pathways. Since the introduction of phenylalanine in
the cell culture medium increased the yield of diosgenin by about 100%. The
degree of accumulation of secondary metabolites are also affected by light,
temperature, pH, and with a suspension suspending cultivation - aeration and
agitation speed vessels, gas composition, etc.
Thus creating for each plant cell culture facilities at the growth stage and the
synthesis of secondary metabolites, it is possible to guarantee receipt of any
product from metabolic activity.
For the accumulation of industrial raw materials by growing the cells and
tissues of plants using callus and suspension cultures, the latter derived from the
callus.
Technology for producing plant material based on callus culture has several
advantages - reliability and stability of the biomass yield and the products of
secondary metabolism, as well as the use of callus for immobilization and
subsequent biotransformation, but has a significant drawback - the need manual
labor.
In Russia, the technology for production of substances of ginseng, Rhodiola
rosea, Unger based on callus cultures. These drugs have been used in medicine,
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cosmetics and food industry. With the implementation of suspension cultivation is
necessary to consider the basic properties of plant cells: plant cells are 50-100
times greater than the fungal cells, resulting in the growth of the cells increase in
size, they appear large vacuole, suspension cultures consist of cell aggregates, the
presence of the cellulose cell wall , respiratory rate.
Growing plant cells are in the blood vessels of various sizes (up to 200
liters) with a stirring system (turbines, rising air, shaking).
Currently, multi-step process used to produce biomass and products of
secondary metabolism:
- Growing in aerated reatore;
- The transfer of cells from one medium to another, richer micro-and macro
nutrients, but devoid of organic additives;
, The subsequent addition of cycle organics.
In general, cells are grown in a batch reactor. To increase the yield of
products of secondary metabolism are developed in relation to methods of
immobilization plant cells, biotransformation. On some models, cell cultures, for
example, corn has been shown that the synthesis and accumulation of secondary
metabolites related to the state of aggregation, it is noted that the closer the cells
and groups of cells to the whole plant, the higher their metabolic potential.
However, there is a lot of data about the inverse relationship between the state of
aggregation and accumulation of secondary metabolites. This is due to two types of
mechanisms. The first is based on the fact that determines the level of aggregation
of cells, and it is sufficient power can be achieved in a slow-growing cultures. The
second mechanism is related to the kinetics of the growth rate and suggests that the
primary and secondary metabolic pathways in different ways compete for
precursors in the fast-and slow-growing cells.
On the basis of the above, it is clear that immobilized cells with a low rate of
growth, the ability to efficient generation of metabolites. One of the conditions for
the immobilization of cells - a metabolite excretion into the medium from which it
can be easily removed. These cultures are cells that produce alkaloids. The
advantages of immobilized cells compared to suspension cultures are:
- Repeated use of biomass;
- Clear separation of biomass from metabolic products;
- Increasing the duration of cultivation stage production;
- Getting a large number of secondary metabolites.
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Another promising way of using plant cell cultures in the pharmaceutical
industry should consider their application for the biotransformation.
Biotransformation - a method that uses enzymes that are localized in the
plant cell, which are able to change the functionality of the added external
chemicals. This method is suitable for increasing the biological activity of the
specific chemical structure and the implementation of a series of specific chemical
reactions by including one or more consistently related enzymes.
Possibility of biotransformation in the synthesis of some compounds has
been shown on the conversion of digitoxin to digoxin cells Digitalis lanata (woolly
foxglove). After a 10-day incubation D.lanata in "growth" medium (Murashige and
Skoog) cell culture was transferred to "a production" environment (8% glucose)
with the substrate for the biotransformation - digitoxin. Under these conditions all
digitoxin for 2 days was transformed into deatsetillantozid C (digoxin) and
purpurglikozid A 88% and 12% respectively.
Digitoxin and digoxin belongs to the group "cardenolides" used for the
treatment of chronic heart disease.
Currently These compounds are in sixth and eighth place in the list of the
most common drugs in United States, but the use of digoxin is preferred because of
its lower toxicity compared to that of digitoxin. Both compounds in the U.S. is
produced by extracting the plantation grown plants, but it stands out mainly
digitoxin.
Undifferentiated culture do not form Digitalis cardiac glycosides, but can
perform certain biotransformation reactions of substrates that have been added to
the culture medium. Biotransformation of digitoxin to digoxin is due to the 12hydroxylation reaction catalyzed by an enzyme found in the cells of Digitalis
lanata. The work was carried out using free undifferentiated suspension cultures in
Germany in 1977, and to date, put into production, made out of digoxin within the
700 g / L in 20-liter reactor within 17 days of cultivation. Thus, the major problems
associated with the biotransformation of cardiac glycosides Digitalis lanata cells
currently allowed. However, further development of this area should be further
selection of specialized cell lines and optimization of the conditions of cultivation,
reducing fermentation time and extend the life of cells. Basic conditions for the
transfer of laboratory methods of cultivation of plant cells in industrial production is economically viable and relatively simple technology of cell culture and
isolation of the final products.
For example, production aymalina through meristem culture Rauwolfia
became real when, in the course of breeding and selection were obtained subclones
of cells that synthesize this alkaloid is much higher than the original parent strains.
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Production based on the serpentine suspension cultures partially
differentiated cells meristem Catharatus roseus was effective and economically
justified only after received subclones able to accumulate over 10 daily cycle of
growing up to 25 g of dry matter per 1 liter of suspension culture.
A similar situation took place in the organization of the biotechnological
production of tincture of ginseng. Yield of the biological substance in terms of dry
matter ginseng callus was lower than that of ginseng obtained by plantation
cultivation, about 3-4 times.
Production of bio-ginseng has become economically viable only after it was
possible to increase the productivity of callus cultures, keeping unchanged
reactogenic properties extracted medicinal tinctures. It turned out that the more
differentiated cells in the meristem culture, the higher their productivity. The
technology of the culture of so-called "bearded" roots, where growth conditions in
a cluster of cells arise subpopulations with increased differentsirvkoy. These
populations are the most productive on biologically active substances.
VECTORS genetic engineering of plants
In genetic engineering of plants are used as vectors Ti-plasmid constructed
by Agrobacterium Agrobacterium tumifaciens, and Gauls-spreader
Natural Ti-plasmid system of gene transfer in plants needs to be modified
before it can be used. Universal vector system based on the T-DNA should:
a) contain all the signals necessary for the transfer and stable integration into
the nuclear DNA of plants, all of the products required for these processes, a
system for the expression of genes transferred into plants, a marker that helps
selecting transformed cells;
b) contains functions that can affect cell differentiation and regeneration of
plants;
c) describe a simple method of introducing foreign DNA into the vector;
d) to have reliable methods for introducing Ti-plasmid sequences of the
cloned alien X-gene into the plant;
2. Transposed elements (TE).
Are segments of DNA that are autonomously control their own exposure
(cut) from the chromosome and integration of the new site of DNA.
3. Plant viruses.
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Another possibility is the construction of vectors associated with the use of
plants phytoviruses and viroids. Because with recombinant nucleic acids are easier
to manipulate DNA, the real candidates for becoming kaulinovirusy vectors
containing double-stranded DNA geminiviruses containing single-stranded DNA.
DNA viruses that are present only these two groups account for only 1-2%
of the total number of viruses infecting plants.
Modern herbicides are much more efficient and environmentally safer than
their predecessors, but they operate on the vegetation succession, not
understanding where the crop plants, where the weeds, so earlier is mainly used to
planting or after harvest. With the advent of genetic information has become
possible to build into the plant genes that make them insensitive to these
herbicides. Thus, after herbicide treatment weeds are killed, and transgenic crops no.
To give resistance to pests most commonly used Bt-toxin gene, isolated
from the bacterium Bacillus thuringiensis. Preparations of this bacteria for about
50 years used in agriculture as a safe for humans and animals bioinsecticides, but
they quickly lose their activity, and therefore, their share in world production of
insecticides is not more than 2%. The toxin affects the gut bacteria pests that feed
on plants, and with very high specificity. By incorporating a gene plant begins
producing the toxin itself. So, no need to handle hazardous chemicals, crop
insecticides.
Questions for self-checking:
1. What type of metabolites of plants are alkaloids?
2. What are the chemical structures of the most technologically receive with
the help of vegetable producers?
3. name the basic biotechnological form vegetable producers;
4. name the main reasons for the need for the development of
biotechnological plant producers.
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