维生素A生物工程作物

1、What do you get when you cross a rice plant and a daffodil?Riddle:a frankenfooda solution to malnutrition Vitamin AVitamin A has many roles in the body: sight differentiation of epithelial cells sustenance of the immune system supports growth of bones anti-oxidantThe recommended daily allowance is 8

2、00 1000 ug RE/dayThis is easily achieved for Americans.3 raw carrot sticks cup cooked carrots cup broccoli1 medium sweet potato2/3 cup fortified oatmeal cup tomato juice100 million children are suffering from vitamin A deficiencySymptoms of vitamin A deficiency (VAD) include: night blindness inabili

3、ty to recover from a flash of light clumping of skin cells around hair follicles irreversible progressive blindness due to corneal ulcers anemia reduced bone growth generally increased mortality1.31.080.100.060.06250,000-500,000 children go blind each year Half of these children die within one year

4、of becoming blind In communities with VAD, a child is 23% more likely to die and 50% more likely to suffer acute symptoms of measles VAD is an important factor in maternal mortality, poor pregnancies and lactation In some populations night blindness is 10-20% among womenImproving the Vitamin A statu

5、s among these children can: Reduce the risk of mortality from measles by 50% Reduce the risk of mortality from diarrhoeal diseases by 40% Reduce overall mortality by 25-35% Increases iron uptake Improve response to vaccines Reduce birth-defects and cancerHow can we increase the amount of Vitamin A i

6、n the diet of children and women in poverty stricken countries? Must be something that they can grow themselves Inexpensive Easily stored Must be something that they eat a lot of Goal:Genetically modify rice to be a source of Vitamin AThree steps to genetically engineering rice to make Vitamin AUnde

7、rstand the biologyCollect the necessary pieces Engineer the piecesBiology of -carotene production in plantsLycopene (40C) phytoene desaturasez-carotene desaturaseb-carotene (40C)lycopene b-cyclasePhytoene (40C)phytoene synthaseIPP (5C)GGPP (20C)chlorophyllgiberillic acidsterolscell of a flower petal

8、Four enzymes are required to make -carotenephytoene synthasephytoene desaturasez z-carotene desaturaselycopene b b-cyclaseFrom Annual Review of Plant Physiologyand Molecular Biology. Vol. 49, 1998Biology of -carotene production in plantsIPP (5C)GGPP (20C)chlorophyllgiberillic acidsterolscell of a ri

9、ce seedriceStrategy for re-creation of a Vitamin A pathwayphytoene (40C)phytoene synthase Phytoene synthase gene isolated from N. psuedonarcissus This gene is usually turned on only in cells of leaves and of flower petals Goalget this gene to be turned on in the cells of the seed endosperm IPP (5C)G

10、GPP (20C)chlorophyllgiberillic acidsterolsThe controlling element determines thelocation, timing, amount and duration of gene expression control elementcoding regiongene productOverexpression of phytoene synthase throughout the plant is detrimental to normal plant growthUsing a specific controlling

11、element provides expression in desired locationseedphytoene synstorage proteinFlower petal+controllingelementphytoene synthase protein coding regionphytoene synseedphytoene synthaseStrategy for re-creation of a biosynthetic pathwayphytoene synthasephytoene (40C)lycopene (40C) phytoene desaturase-car

12、otene desaturasebacterial phytoene desaturasephytoene synseedIPP (5C)GGPP (20C)chlorophyllgiberillic acidsterolsCollecting the necessary genesseedstorage proteinbacteriabacterial phytoene desaturase+phytoene desseedphytoene desStrategy for re-creation of a biosynthetic pathwayphytoene synthasephytoe

13、ne (40C)bacterial phytoene desaturaselycopene (40C) -caroteneseedphytoene desphytoeneseed lycopene -cyclaseseedlycopeneIPP (5C)GGPP (20C)chlorophyllgiberillic acidsterolsDoes it work?Growth of engineered plants appeared to be normalNon-transformed controlpsy, crtI, lcy transformed plantsNon-transformed controlLine z11bIs the yellow color is due to the presence of carotenoids?Absorbance (450 nm) Do plants produce enough b-