Lec # 10
Plant biotechnology and food
biotechnology
Dr. Shah Rukh Abbas
9-2-2015
The world population grows and
grows ...
A major objective of
plant science is to
increase food
production; current
estimates indicate that
we need to increase
production by 70% in the
next 40 years.
Malnutrition and hunger
disproportionately kill children
In 2004, 60 million people worldwide died.
(Source: World Health Organization, 2008)
Malnutrition and hunger
disproportionately kill children
10 million of them were children
under 5 years of age,
of which 99% lived in low- or
middle-income countries
(Source: The State of the World's Children, UNICEF, 2007)
Malnutrition and hunger
disproportionately kill children
5 million children under the age of 5 die
each year due to undernutrition and
related causes.
That’s one preschool-aged child
dying a preventable death every six
seconds.
Malnutrition and hunger
disproportionately kill children
A lack of adequate vitamin A kills
one million children a year.
(Source: Vitamin and Mineral Deficiency, A Global Progress Report, UNICEF)
Drought stress is compounded by
increasing global temperatures
In warm regions,
crop yields can drop
~3 – 5% with every
1°C increase in
temperature.
One model of mean
temperature increases in
agricultural lands by 2050.
Gornall, J., Betts, R., Burke, E., Clark, R., Camp, J., Willett, K., and Wiltshire, A. Implications of climate change for agricultural
productivity in the early twenty-first century. Phil. Trans. Royal Soc. B: 365: 2973-2989.m
Plant growth is often limited by drought
stress
Image source: IWMI
WHAT CAN SCIENTISTS DO
ABOUT THIS?
Plant scientists can contribute to
the alleviation of hunger
By developing plants that
 are drought or stress tolerant
 require less fertilizer or water
 are resistant to pathogens
 are more nutritious
• Plant biotechnology is a process to produce a genetically
modified plant by removing genetic information from an
organism, manipulating it in the laboratory and then
transferring it into a plant to change certain of its
characteristics .
• It chiefly involves the introduction of foreign genes into
economically important plant species, resulting in crop
improvement and the production of novel products in plants.
•
The goal of plant breeding is to combine desirable traits from
different varieties of plants to produce plants of superior
quality.
• A transgenic crop plant contains a gene or genes which have
been artificially inserted instead of the plant acquiring them
through pollination.
• The inserted gene sequence (known as the transgene) may
come from another unrelated plant, or from a completely
different species.
• Example transgenic Bt corn, for example, which produces its
own insecticide, contains a gene from a bacterium.
• Corn and soybean to resist pest in US are in the forefront of
Biotechnological revolution.
Plant biotechnology techniques
A. Selective breeding : by crossing two members of the same
species which has dominant alleles for particular genes such as long life
and quick metabolism in one organism crossed with another organism
possessing genes for fast growth and high yield. when they are crossed
they will produce at least some offspring, called hybrid, that will show
ALL of these desirable characteristics.
B. Gene cloning provides a new dimension to crop breeding by
enabling directed changes to be made to the genotype of a plant,
circumventing the random processes inherent in conventional breeding.
Two general strategies have been used:
1. Gene addition, in which cloning is used to alter the characteristics
of a plant by providing it with one or more new genes; e.g. Plants
that make their own insecticides, or herbicide resistant crops. (BT
crops).
2. Gene subtraction, in which genetic engineering techniques are
used to inactivate one or more of the plant’s existing genes; e.g.
silencing the gene for fruit ripening in tomato to increase shelf life
Methods to transfer gene (Plant
transformation)
1. Biolistic approach In the "biolistic" (a cross between
biology and ballistics )or "gene gun" method, microscopic
gold beads are coated with the gene of interest and shot into
the plant cell with a pulse of helium.
• Once inside the cell, the gene comes off the bead and
integrates into the cell's genome. Its also called cellular target
approach.
Biorad's Helios gene gun
2. Electroporation of protoplasts (cells grown
without a cell wall): Plant cells could be "electroporated"
or mixed with a gene and "shocked" with a pulse of
electricity, causing holes to form in the cell through which
the DNA could flow. The cell is subsequently able to repair
the holes and the gene becomes a part of the plant genome.
3. Agrobacterium-mediated gene transfer
Agrobacterium tumefaciens is a
• Common soil bacterium acts as a natural plant parasite
• Multiply rapidly after inducing an infection
• Result in tumor formation; The “Crown galls”
And so their natural ability of gene transfer is manipulated for genetic
engineering of plants
•
Agrobacterium tumefaciens is a common soil bacterium
that causes crown gall disease by transferring some of its
DNA to the plant host.
•
The transferred DNA (T-DNA) which is part of its Tumour
inducing plasmid (Ti-plasmid )is stably integrated into the
plant genome, where its expression leads to the synthesis of
plant hormones and thus to the tumorous growth of the
cells.
•
After discovering this process, scientists were able to
"disarm" the bacterium, put new genes into it, and use the
bacterium to harmlessly insert the desired genes into the
plant genome
How does it transfer?
Ti-plasmid T-DNA for gene transfer
Flavr SavrTM tomato-First GM plant
• Introduced in 1994 by Calgene Inc.
We need plants that grow well
even under stressful conditions
Heat and drought
reduce plant yields
We need plants that grow well
even under stressful conditions
Heat and drought
reduce plant yields
More land must be cleared to
grow more crops
We need plants that grow well
even under stressful conditions
Heat and drought
reduce plant yields
Removing trees to make way
for crops puts more CO2 into
the atmosphere
More land must be cleared to
grow more crops
Altering a single gene can
increase plants’ drought
tolerance
Drought-resistant
Wild-type
Well-watered
10 days drought
20 days drought
After re-watering
Yu, H., Chen, X., Hong, Y.-Y., Wang, Y., Xu, P., Ke, S.-D., Liu, H.-Y., Zhu, J.-K., Oliver, D.J., Xiang, C.-B. (2008) Activated
expression of an Arabidopsis HD-START protein confers drought tolerance with improved root system and reduced stomatal density.
Plant Cell 20:1134-1151.
Plants can make safe and
inexpensive edible vaccines and
antibodies
OR
?
Protoplast Fusion (Plant tissue culture)
• Plant tissue culture is the cultivation of plant cells, seeds,
organs, tissues or protoplasts on specifically formulated
nutrient enriched media in sterile conditions.
• Under appropriate conditions, an entire plant can be
regenerated from each single cell, permitting the rapid
production of many identical plants.
• Protoplast is a cell without cell wall
• Protoplasts are capable of fusing; forms somatic hybrids of
even genetically incompatible plants
• Hybrid protoplasts are then regenerated by tissue culture into
whole hybrid plants .
• Boccoflower is a hybrid between broccoli and cauliflower.
Basis for Plant Tissue Culture
• Two Hormones Affect Plant Differentiation:
– Auxin: Stimulates Root Development
– Cytokinin: Stimulates Shoot Development
• Generally, the ratio of these two hormones can
determine plant development:
–  Auxin ↓Cytokinin = Root Development
–  Cytokinin ↓Auxin = Shoot Development
– Auxin = Cytokinin = Callus Development
Control of in vitro culture
Cytokinin
Leaf strip
Adventitious
Shoot
Root
Callus
Auxin
Factors Affecting Plant Tissue Culture
• Growth Media
– Minerals, Growth factors, Carbon source, Hormones
• Environmental Factors
– Light, Temperature, Photoperiod, Sterility, Media
• Explant Source
– Usually, the younger, less differentiated explant, the better for
tissue culture
– Different species show differences in amenability to tissue culture
– In many cases, different genotypes within a species will have
variable responses to tissue culture; response to somatic
embryogenesis has been transferred between melon cultivars
through sexual hybridization
Three Fundamental Abilities of Plants
 Totipotency
the potential or inherent capacity of a plant cell to develop into an
entire plant if suitably stimulated.
It implies that all the information necessary for growth and
reproduction of the organism is contained in the cell
 Dedifferentiation
Capacity of mature cells to return to meristematic condition and
development of a new growing point, follow by redifferentiation which
is the ability to reorganize into new organ
 Competency
the endogenous potential of a given cells or tissue to develop in a
particular way
Types of In Vitro Culture
 Culture of intact plants (seed and seedling culture)
 Embryo culture (immature embryo culture)
 Organ culture
1. shoot tip culture
2. root culture
3. leaf culture
4. anther culture
 Callus culture
 Cell suspension culture
 Protoplast culture
Tissue Culture Applications
Micropropagation
dihaploid production
Protoplast fusion
Genetic engineering