Genetically Engineered Plants - lectureug4

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14 Δεκ 2012 (πριν από 4 χρόνια και 4 μήνες)

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GENETICALLY ENGINEERED
PLANTS

Momina

Masood


Sumaiya

Gul

INTRODUCTION



Engineering of crop plants is one of the rapidly expanding area of
biotechnology.




Genetic engineering is used to add a variety of new traits to
important crops.




Thousands of field trials being conducted, mostly in the United
States.




Six different types of traits have been introduced into plants.




Twelve genetically engineered plant species have been approved
for commercialization in the United States.




Traditionally, most of such genetically engineered plants were
tobacco, petunia, or similar species with a relatively limited
agricultural application.



During the past decade it now has become possible to transform
major staples such as corn and rice and to regenerate them to a
fertile plant

Traits Introduced in Plants


Traits Genetically modified
plants



Insect resistance Corn, cotton, potato, tomato.



Herbicide resistance Corn, soybeans, cotton, flax,





rice, sugar beets, canola.



Virus resistance Squash, papaya, potato.


Delayed fruit ripening Tomato.


Altered oil content Canola, soybeans.


Pollen control Corn, chicory.

Genetically Engineered
S
pecies
A
pproved for
Commercialization.


Canola



Corn,

including

popcorn

and

sweet

corn

but

not

blue

corn


Cotton


Flax


Papaya



Potatoes



Red
-
hearted

chicory



Soybeans



Squash

(yellow

crookneck)



Sugar

beet



Tomatoes,

including

cherry

tomatoes
.



Currently,

up

to

85

percent

of

U
.
S
.

corn

is

genetically

engineered
.


91

percent

of

soybeans

and

88

percent

of

cotton

(cottonseed

oil

is

often

used

in

food

products)
.


According

to

industry,

up

to

95
%

of

sugar

beets

are

now

GE
.



Genetic

engineering

of

plants

is

much

easier

than

that

of

animals
.

There

are

several

reasons

for

this
:



(
1
)

there

is

a

natural

transformation

system

for

plants

(the

bacterium

Agrobacterium

tumefaciens
),



(
2
)

plant

tissue

can

redifferentiate

(a

transformed

piece

of

leaf

may

be

regenerated

to

a

whole

plant),

and



(
3
)

plant

transformation

and

regeneration

are

relatively

easy

for

a

variety

of

plants

Plant Transformation


Alteration of the genetic makeup of plants



Most Common
Methods

Biolistic

Method

A.
Tumefaciens

Mediated
Method

The
Biolistic

Method

Integration
of DNA
into
Genome

Shooting
under high
pressure

Binding
DNA to
some
particles

Shortcoming


The method can cause
serious damage to the
cellular tissues

Agrobacterium

tumefaciens


Natural plant parasites


Multiply rapidly after inducing an infection


Result in tumor formation; The “Crown galls”


Their natural ability of gene
transfer is manipulated for
genetic engineering of plants

The Trouble Maker…or not?

Transferred
DNA

Virulence
genes

Tumor
inducing
Plasmid

The Ti
-
Plasmid

How Does It do it?

We Are More Smart!

The Two Methods

The First Genetically Modified Plant

Flavr

Savr

The Most Genetically Modified Ones

Nicotiana

tobaccum

Arabidopsis thaliana

Who Monitors it in USA?

Yes They Work!


During testing of
transgenic soybean
that had been inserted with a gene
from Brazil nut. The inserted gene
was not detected to translate a known
allergen but the allergic nature of the
protein was detected in the people who
were allergic to Brazil nut.

In Europe; The Assessment

Plants Allowed for Cultivation

Who Regulates it in Australia?

Agricultural Impacts


Threat to Farmers and food producers


Different legislations for GM derived and
conventional products


Co
-
existence and traceability

Genetically Modified Alfalfa

Cultivation of Genetically Modified
Alfalfa has been approved by United
States Agriculture Secretary Tom
Vilsack , as of January 2012…



The New Anti
-
Christ
-
Ghanaian Priest

A Ghanaian priest has warned his followers
against the consumption of Genetically Modified
foods because according to him these are not only
harmful but upset God’s divine plan for the
world…


The Ecological Risks and Benefits of
Genetically Engineered Plants



L. L.
Wolfenbarger

and P. R.
Phifer


Abstract:

Discussions

of

the

environmental

risks

and

benefits

of

adopting

genetically

engineered

organisms

are

highly

polarized

between

pro
-

and

anti
-
biotechnology

groups,

but

the

current

state

of

our

knowledge

is

frequently

overlooked

in

this

debate
.

A

review

of

existing

scientific

literature

reveals

that

key

experiments

on

both

the

environmental

risks

and

benefits

are

lacking
.

The

complexity

of

ecological

systems

presents

considerable

challenges

for

experiments

to

assess

the

risks

and

benefits

and

inevitable

uncertainties

of

genetically

engineered

plants
.

Collectively,

existing

studies

emphasize

that

these

can

vary

spatially,

temporally,

and

according

to

the

trait

and

cultivar

modified
.


Foreign Gene Expression and Challenges


Gene

expression

is

the

process

by

which

information

from

a

gene

is

used

in

the

synthesis

of

a

functional

gene

product
.


These

products

are

often

proteins,

but

in

non
-
protein

coding

genes

such

as

ribosomal

RNA

(rRNA),

transfer

RNA

(tRNA)

or

small

nuclear

RNA

(snRNA)

genes
.



The

product

is

a

functional

RNA
.


Any

rational

programme

of

plant

improvement

by

gene

transfer

method

must

be

based

on

how

genes

are

organized

in

a

plant

genome

and

how

their

expression

is

regulated
.



DNA/RNA

hybridization

experiments

which

compare

mRNA

sequences

on

a

tobacco

plant

show

that

some

mRNAs

are

organ

specific



Some

are

expressed

in

more

than

one

organ

and

some

are

expressed

in

all

organs
.



Regions

of

DNA

are

involved

in

transcriptional

and

translational

control

of

a

gene
.



The

5
`

prime

end

of

promoter

region

is

involved

in

initiation

of

transcription
.



Other

elements

include
:

enhancer

or

silencer

regions

are

also

involved

in

regulation

of

expression
.


Factors determining regulation of gene



Factors

determine

temporal

and

spatial

regulation
:

1.
A

gene

must

be

delivered

to

all

cells

and

stably

maintained

for

transmission

to

progeny
.


2.
The

promoter

region

must

be

recognized

by

host

cell

so

that

RNA

polymerase

binds
.


The

promoter

can

be

regulated

or

constitutively

expressed

depending

on

the

type

of

gene

and

desired

outcome
.


3
.

Termination

and

polyadenylation

signal

must

also

be

provided
.


Thus,

consideration

of

apropriate

regulatory

region

of

foreign

gene

introduced

into

plant

cells

is

important
.

Regions

include

enhancers

and

promoters

as

well

as

terminator

of

transcription

and

3
`

polyadenylation

signals
.

Challenges



Different

promoter

regions

are

used

for

different

outcomes
.



for

strong

constitutive

expression

the

cauliflower

mosaic

virus

35
S

promoter

is

often

used
.



a

highly

regulated

promoter

responds

to

certain

signals

e
.
g

heat,

light

and

nutrients

by

turning

the

genes

on
.



the

promoter

for

the

gene

encoding

1
,
5

bisphosphate

carboxylase

small

subunit

is

light

regulated

,

that

is

activated

n

the

presence

of

light
.


If

a

gene

product

is

to

be

produced

in

a

specific

region

of

the

plant,

tissue

specific

regulatory

regions

must

be

included

in

the

construct
.


Another

challenge

to

be

considered

is

the

codon

usage
.




the

codons

and

amino

acids

used

by

an

organism,

some

codons

are

used

more

than

others

depending

on

the

species

of

plants

or

other

organism
.



genes

from

nonplant

sources

especially

may

specify

amino

acids

that

do

not

match

the

plant’s

tRNA

and

amino

acids

pools
.



researchers

use

codon

engineering
:

they

resynthesize

the

donor

genes

if

the

codons

or

amino

acids

do

not

match

the

host

system
.


Codon

engineering

helps

ensure

that

the

host

plant

will

have

the

appropriate

tRNAs

and

amino

acids

to

synthesize

the

protein
.


To

increase

the

production

of

Bacillus

thuringienesis

toxin

by

potato,

tomato,

rice

and

cotton,

the

Bt

toxin

gene

has

been

engineered

to

match

the

host

plants

translation

machinery

and

to

remove

incompatible

sequences
.

Challenges


Some

genes

are

organ
-
specific
.

The

phaseolin

storage

protein

gene

from

the

French

bean,

Phaseolus

Vulgaris
.

This

gene

is

normally

expressed

in

the

embryo

of

the

developing

bean

seed
.



the

gene

is

expressed

at

very

low

levels

in

other

organs
.



expression

of

seed

storage

protein

of

soybean

has

been

examined
.

The

gene

containing

8
.
5

kb

of

the

5
`

flanking

sequence

was

expressed

in

immature

embryos

but

not

in

leaves
.



the

expression

of

a

number

of

genes

is

modulated

by

environmental

or

biological

stimuli

in

higher

plants
.



expression

of

soybean

and

maize

heat

shock

genes

has

been

found

to

be

heat

inducible

in

heterologus

plant

tissue

Agronomically Useful Genes



Genetic

engineering

has

a

great

impact

on

the

improvement

of

crop

species
.



Plant

breeding

has

played

a

major

part

in

providing

plants

with

better

resistance

to

insect

pests

and

with

enhanced

yields
.



Some

degree

of

success

has

already

been

realized

in

:



Engineering

selective

resistance

to

herbicides,

herbicides

inhibit

plant

growth

by

blocking

the

biosynthesis

of

important

amino

acids
.

Knowledge

of

the

sites

of

inhibition

has

lead

to

the

use

of

gene

transfer

strategies

to

engineer

resistance
.



Engineering

resistance

to

viral

diseases

and

insect

pests,

insect

resistance

in

transgenic

plants

has

been

achieved

through

the

expression

in

plants

of

the

insect

toxin

gene

of

bacillus

thurengenesis
.



Learning Means
Enlightenment