PREPARATION OF PLANT
TISSUE CULTURE MEDIUM
AIM: To prepare Murashige and Skoog (MS) media for plant tissue culture.
INTRODUCTION:
Murashige
and Skoog medium or (MSO or MS0 (MS-zero)) is a most
commonly used plant growth medium
in the laboratories for cultivation of plant cell culture.
MSO was invented by plant scientists Toshio
Murashige and Folke K.
Skoog in 1962 during Murashige's search for a new plant growth regulator.
The culture medium is one of the most important components of plant cell and
tissue culture method. The successful application of plant culture medium with
its right composition in addition to its components is one of the most
important pre-requisite of a plant tissue culture experiment. Another important
function of the culture medium is to provide the right physical environment for
cells and tissues to grow on solid medium. The media also performs a function
like soil by providing a physical support matrix. All plant cells require
water, nutrients and plant growth regulators.
The requirements of
plant cell culture may be subdivided into 3 groups:
1. Inorganic
nutrients
2. Organic
nutrients
3. Plant
growth regulators
Inorganic nutrients:
Inorganic nutrients are mineral elements and based on their essential
concentration they are classified into 2 groups: macroelements, present in
large supplies (mM concentration) and microelements as trace elements.
MACROELEMENTS:
·
Nitrogen: supplied in the form of
nitrate ions and ammonium ions (KNO3 and NH4NO3). Nitrogen is a component of protein, nucleic acid, chlorophyll, some coenzymes
and is required in greatest amounts.
·
Sulphur: supplied in the form of
sulphate ions. Sulphur is a vital component of amino acids, vitamins,
cofactors, iron sulphur protein (electron carrier).
·
Phosphorous: supplied as a phosphate ion
(PO4). Added as Na/K dihydrogen phosphate. It is an essential
component of nucleic acid, phospholipids and in energy rich compounds.
·
Cations: supplied as KNO3
salt. Potassium functions as osmoregulators, cation-anion balance, and pH
stabilization.
MICROELEMENTS:
·
Iron: added as iron sulphate [Fe (III)].
EDTA is usually used in conjunction with iron sulphate. This complex with iron
so as to allow slow and continuous release of iron into the medium. Uncomplexed
iron usually precipitates out of the medium as ferric oxide. It is required by
the plant for chlorophyll synthesis as a constituent of cytochrome and Fe-S
protein.
·
Boron: added as boric acid. It is a
component of cell wall required for cell division of optical meristem.
·
Cobalt: added as cobalt chloride. It is
a component of some vitamins.
·
Copper: added as copper sulphate. It as
serves as an enzyme cofactor and function in electron reactions.
·
Iodine: improves growth of roots and
callus, added in the form of KI.
·
Manganese – Added in the form of MnSO4.
Manganese is found in metalloproteins.
·
Molybdenum – Added as sodium Molybdate.
It is an enzyme cofactor.
·
Zinc – Added as ZnSO4
required for activity of various enzymes.
Organic Nutrients:
While green plants are autotrophic,
most culture system in early stages is heterotrophic. Plant culture system
requires an organic carbon and energy source and complex organic molecule such
as vitamins and cofactors for healthy growth.
·
Carbon Source: Sucrose is most commonly
used sugar in plant tissue culture media, but glucose, fructose and sorbitol
are used in some formulations.
·
Vitamins and Co-Factors: two vitamins,
thiamine (B1) and myoinositol( Vit B)
are essential for plant tissue culture. Other vitamins such as biotin,
pantothenic acid (niacin), pyridoxine (Vit B6), folic acid, ascorbic acid (Vit C)
and tocopheryl acetate (Vit E) are added to the media.
·
Complex Organic Supplements: complex
additions such as banana powder and liquid endosperm of coconut are frequently
used in plant tissue culture media such as kinetin, benzyl aminopurine and
zeatin media to improve growth.
Plant Growth Regulators:
There are 5 main classes of plant
growth regulators.
·
Auxins: they promote both cell division
and cell growth. Auxins are synthesized in stems and root spaces and transport
along the plant axis. Auxins commonly used in plant tissue culture are 2, 4-dichlorophenoxy
acetic acid (2, 4-D), Indole 3-acetic acid (IAA), Indole-3-butyric acid (IBA),
1-napthalene acetic acid (NAA). Auxins together with cytokines are used in
plant tissue culture to control differentiation and morphogenesis.
·
Cytokinins: they promote cell division,
growth and development. Naturally occurring cytokinins are purine derivatives.
They are frequently used in plant tissue culture media such as kinetin, benzyl
aminopurine and zeatin.
·
Gibberellins: Major action of
gibberillin is stimulation of cell stem elongation and flowering. Gibberillic
acids are commonly used in plant tissue cultures (GA, GA4, and GA3).
·
Abscissic Acid: Primarily involved in
water-stem responses, seed germination and enhances somatic embryogenesis.
·
Ethylene: is gaseous and is associated
with fruit ripening in climatic fruits.
Support Matrices of
Gelling Agents:
In some plant cell and
tissue culture system a solid or semi solid matrix is needed to support tissue explants
while allowing contact with media. The most commonly used support matrices are
formed from gelling agents such as agar, agarose, gelatin, gelatin gums.
Agar is the most
commonly used gel in plant tissue culture. It is a complex polysaccharide
extracted from red algae (Rhodophyceae)
and comprises 2 fractions-agar (70%) & agar pectic (30%). Agarose in the
jelly fraction and consists of a polymer of D-galactose and 3,
6-anhydrogalactose monosaccharide units. Agropectin is the non gelling fraction
and consists of polymer of sulphur.
The required basal
medium can be prepared by either dissolving the commercially available basal
salt mix on by preparing the mix from individual ingredients. An alternative is
to prepare macronutrients & micronutrients stock solution and store these
at 40 C. Until used, organic compounds should not be stored in
solution for more than 2 weeks. Heat labile compounds such as plant growth
regulator, antibiotics are added to the medium after autoclaving.
MATERIALS AND REQUIREMENTS:
·
Distilled water, sucrose, gelling agent,
1M NaOH or 1M HCl to adjust the pH, micronutrients stock, macronutrients stock,
organic compound stock.
·
Equipment – Balance, pH meter,
autoclave, LAF cabinet.
·
Glassware – conical flask, phyta jars,
beakers, pipettes.
PROCEDURE:
·
Add approximately half the volume of
water to a conical flask
·
Weigh out the appropriate amount of
basal salts (4.4g) or measure out appropriate volume of stock solution .Add the
water and 30 g sucrose
·
When all solids have dissolved , adjust
the pH 5.7 using 0.1M NaOH or HCl
·
Make up the volume to 1 litre using
distilled water
·
Weigh 10 g agar and add to the above
medium
·
Melt the agar by heating
·
Divide the medium into tissue culture
bottles and close the bottles with screw caps
·
Sterilize the culture bottles by
autoclaving at 1210 C for 15 min 15 psi
·
After autoclaving, ensure the caps are
immediately lightened.
PREPARATION
OF HORMONE STOCKS:
·
Weigh out 0.3g of IAA
·
Sterilize the IAA by placing under UV
light for 30 mins. Transfer to a sterile volumetric flask.
·
Dissolve the IAA in few drops of ethanol
and make up the volume to 100 ml using sterile distilled water.
·
Weigh out 0.1mg of kinetin and sterilize
under UV light
·
Transfer to a flask and dissolve in 100 ml of
sterile distilled water
·
Add 30 ml of IAA stock and 1.5 ml of
kinetin stock to each bottle aseptically. Mix well and allow the contents to
solidify and use immediately or store at 40C .
Murashige and Skoog
(MS) media composition:
Macroelements
|
g
|
NH4NO3
|
1.65
|
KNO3
|
1.90
|
CaCl2.2H2O
|
0.44
|
MgSO4.7H2O
|
0.37
|
KH2PO4
|
0.17
|
Microelements
|
mg
|
FeSO4.7H2O
|
27.80
|
Na2EDTA.2H2O
|
33.60
|
KI
|
0.83
|
H3BO4
|
6.20
|
MnSO4.4H2O
|
22.30
|
ZnSO4.7H2O
|
8.60
|
Na2MoO4.2H2O
|
0.25
|
CuSO4.5H2O
|
0.025
|
CoCl2.6H2O
|
0.025
|
Organic supplements
|
mg
|
Myoinositol
|
100
|
Nicotinic
acid
|
0.05
|
Pyridoxine
HCl
|
0.05
|
Thiamine
HCl
|
0.05
|
Glycine
|
0.20
|
Sucrose
|
30g
|
Agar
|
10g
|
Dissolve the
microelements, macroelements and organics in 800ml of distilled water. Add the
required hormone solutions. Adjust the medium pH to 5.7 by adding 1M NaOH or 1M
HCl. Add additional distilled water to adjust the final volume to 1litre. Add
the agar and heat the medium to dissolve the agar. Dispense the medium into
culture tubes or vessels and autoclave for 20minutes at 121°C.
Half (1/2) M S Media :
REFERENCE:
Half (1/2) M S Media :
Some
refer to half-MS as half of everything (macro, micro, sucrose, etc.).
Some use half macro and micro and full sucrose. This term has not been standardized in the literature.
Generally Half M S media uses half macro elements only....The micro elements are full strengh...
REFERENCE:
Biotechnology: Fundamentals and Applications; S.S.Purohit and S.K.Mathur; Agro
Botanical Publishers; page no.s 112-117.
http://plant-tc.cfans.umn.edu/listserv/2002/log0205/msg00141.html
http://plant-tc.cfans.umn.edu/listserv/2002/log0205/msg00141.html