12. BIOTECHNOLOGY AND ITS APPLICATIONS
Biotechnology has many applications such as biopharmaceuticals,
therapeutics, diagnostics, genetically modified crops, processed food,
bioremediation, waste treatment and energy production.
Biotechnology
has 3 critical research areas:
a.
Providing the
best catalyst in the form of improved organism
usually a microbe or enzyme.
b.
Creating
optimal conditions through engineering for a catalyst
to act.
c.
Downstream
processing technologies to purify the
protein/organic compound.
APPLICATIONS IN AGRICULTURE
3 options for increasing food production:
a. Agro-chemical
based agriculture: It uses fertilizers &
pesticides. Expensive. Causes environmental pollution.
b. Organic
agriculture: Expensive.
c. Genetically
engineered crop-based agriculture: It uses
genetically modified crops. Genetically
Modified Organisms (GMO)
are the plants, bacteria, fungi & animals whose genes are altered by manipulation.
Advantages of genetic modification in
plants:
·
It makes crops more tolerant to
abiotic stresses (cold, drought, salt, heat etc.).
·
Pest-resistant crops reduce the use
of chemical pesticides.
·
It reduces post-harvest losses.
·
It increases efficiency of mineral
usage by plants (it prevents early exhaustion of soil fertility).
·
It enhances nutritional value of
food. E.g. Golden rice (Vitamin A enriched rice).
·
To create tailor-made plants to
supply alternative resources (starches, fuels, pharmaceuticals etc.) to
industries.
Pest Resistant Plants
-
They act as bio-pesticide.
-
It reduces the need for
insecticides.
-
E.g. Bt cotton, Bt corn, rice,
tomato, potato, soyabean etc.
Bt Cotton:
- Some strains of Bacillus thuringiensis have
proteins that kill
insects like coleopterans (beetles), lepidopterans (tobacco budworm, armyworm) &
dipterans (flies, mosquitoes).
- B. thuringiensis forms an insecticidal
protein (Bt toxin) crystal during a phase of their growth. It does not kill
the Bacillus as it exists as inactive protoxins.
- When an insect ingests the toxin, it becomes active due to alkaline
pH of the gut which solubilise the crystals. Toxin binds to surface of mid-gut
epithelial cells creating pores. It causes cell swelling and lysis and death of
the insect.
- Bt toxin genes were isolated from B. thuringiensis and incorporated into
crop plants such as cotton.
- Most Bt toxins are insect-group
specific. They are coded by cry genes. E.g. proteins encoded by cryIAc
& cryIIAb genes control cotton bollworms. Protein of cryIAb gene
controls corn borer.
Nematode resistance
in tobacco plants:
- A nematode Meloidogyne incognita infects
the roots of tobacco plants causing a reduction in yield.
- It can be prevented by RNA
interference (RNAi) strategy.
- RNAi is a method of cellular defense in all eukaryotic organisms. It
prevents translation of a specific mRNA (silencing) due to a complementary
dsRNA molecule.
- The source of this complementary RNA
is from an infection by RNA viruses or mobile genetic elements (transposons)
that replicate via an RNA intermediate.
- Isolate Nematode-specific genes
(DNA). It is introduced into host plant using Agrobacterium vectors. It
produces both sense & anti-sense RNA in host cells. These RNAs are complementary.
So they form double stranded (ds) RNA. It initiates RNAi and silences the
specific mRNA of nematode. Thus the parasite cannot survive in a transgenic
host expressing specific interfering RNA.
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