Golden Rice.

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16 Δεκ 2012 (πριν από 4 χρόνια και 7 μήνες)

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GOLDEN RICE.

A possible end to vitamin A deficiency.

BACKGROUND.


hundreds of millions of people are starving and
suffering from micronutrient malnutrition.


Using genetic engineering technology, we have
the potential to prevent this.


Every day 24,000 people die because of
poverty
-
based lack vitamins, minerals and
essential amino
-
acids.


BACKGROUND.


the majority of the world’s poor try to survive on
staple foods.


Rice, for example, is the basic staple crop for
half the humankind.


VITAMIN A DEFICIENCY.


VAD for short


Responsible for around one to two million
deaths worldwide.


Five hundred thousand cases of blindness


Fifty percent of individuals who became blind
die within a year.


Impacts the immune system.

VAD


coronary heart disease.


certain cancers (e.g., cancer of the lungs, prostate,
etc.)


various childhood diseases which result in death
(e.g., due to a weakened immune system).


childhood blindness (estimated to afflict 350,000
-

500,000 children per year).


macular degeneration, a leading cause of
blindness in older people.


GOLDEN RICE


Designed to produce beta carotene.


Precursor to vitamin A.


Normally not found in rice.


Problematic because places such as
Bangladesh, 80 percent of people’s energy
intake comes from rice.

CHALLENGE.


Until then, only single gene transfers had been
done.


The entire biochemical pathway, from
geranyl
-
geranyl
-
pyrhophosphate
, to beta
-
carotene had
to be engineered.


Final goal to produce beta
-
carotene in rice
endosperm.


GOLDEN RICE.


Ingo
Potrykus

and Peter Beyer.


Utilized
Agrobacterium

tumefaciens

bacteria to
genetically engineer rice plant.




T
-
DNA’, part of the tumor
-
inducing (
Ti
) plasmid
of the soil bacterium,
Agrobacterium
.


The
Ti

plasmid naturally invades plant cells,
inserting the
T
-
DNA into the plant cell genome,
and causing the cell to develop into a plant
tumor or gall.



The artificial gene construct is spliced in
between the left and right borders of the
T
-
DNA
vector.


The borders of the
T
-
DNA are ‘hotspots’ for
recombination.


Ultimately why the vector can invade the plant’s
genome and carry its hitch
-
hiker gene construct
along with it.


ENZYMES.



Psy

(
phytoene

synthase
) from daffodil


(Narcissus pseudo narcissus)


Crt1 (carotene
desaturase
) from the soil bacterium
Erwinia

uredovora


Catalyze the biosynthesis of beta
-
carotene from
geranyl
-
geranyl

diphosphate
.


The insertion of a
lyc

(
lycopene

cyclase
) gene was
thought to be needed, but research showed it was
already being produced in wild
-
type rice endosperm

1.
Phytoene

synthase
-

from daffodil (narcissus) which converts
geranylgeranyl
-
diphosphate

into
phytoene
.


2
. "CRTL" gene
-

from
Erwinia

uredovora
, which codes for
phytoene

desaturase
, which causes the rice plant to convert
phytoene

(a "light harvesting"
carotenoid

involved in
photosynthesis) into
lycopene

(a
carotenoid

which is then
utilized by the rice plant in the production of beta carotene).



3
.
Lycopene

beta
-
cyclase

-

from daffodil, which converts
lycopene

into beta carotene.


FINAL GENE
CONSTUCT
.

Ubi1, maize
polyubiquitin

promoter


Glu
, rice endosperm
-
specific
glutelin

promoter to ensure that the gene was only
expressed in the endosperm of the rice
.


tpSSU
, a small subunit transit peptide for chloroplast
localization


Crt1 and
Psy
.


Pmi
,
phosphomannose

isomerase

gene from E. coli for positive selection.


Nos
, as the terminator



The original golden rice was called SGR1, and
under greenhouse conditions it produced 1.6
µg/g of
carotenoids
.


In 2005 researchers at the biotechnology
company
Syngenta
. Created a variation on
golden rice


Golden rice 2 produces 23 times more
carotenoids

than golden rice.


Golden rice was developed to provide a low
cost vitamin supplement in countries with
individuals suffering from vitamin A deficiency.


Vitamin A supplementation programs take
place internationally through pills and
injections.



No single (or even a few) food items can
provide all the nutrients we need.




Golden Rice can now provide 20
-
40%of the
daily requirement of vitamin A


The United Nations (UNICEF) estimates that 1
to 2 million deaths of children age 1
-
4 years old
could be prevented annually around the world.




References


Ye X, Al
-
Babili

S,
Klöti

A, Zhang J, Lucca P, Beyer P,
Potrykus

I
(2000) Engineering the
provitamin

A (beta
-
carotene)
biosynthetic pathway into (
carotenoid
-
free) rice endosperm.
Science 287: 303
-
305.





the science behind golden rice
<
http://www.goldenrice.org/Content2
-
How/how1_sci.html
>





the golden rice scandal unfolds <
http://www.i
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>