Creation of Bt plants

creation of Bt plants,golden rice& flvr savr

1. WELCOME TOPIC: CREATION OF BT PLANTS,GOLDEN RICE &FIAVR SAVR TOMATO SIJI SKARIAH PG 2 BOTANY ST.THOMAS COLLEGE KOZHENCHERRY

2. Improvement in agricultural production and the food and nutrition situation depends on land water and energy resources. From 1970 a new type of research started with the aim of producing new varieties of plants by genetic recombination techniques. They are genetically engineered plants They have acquired a new trait from the introduced DNA and inherit the trait for many generations.

3. The new plants produced by such techniques are supposed to be:- Virus resistant plant Insect resistant plants, Herbicide resistant plant

4. BACILLUS THURINGIENSIS (BT) Soil bacterium; ubiquitous Different strains produce their own insecticide proteins. The protein is called as cry protein for its crystal form. Each cry protein selectively affects insects belonging to a particular order ( Lepidoptera( moths,butterflies ), Diptera (flies and mosquitoes) etc)

5. Bt Crops Bt plants are generally said that insect resistant transgenic plants. Insect attack is a serious agricultural problem leading to yield losses and reduced product quality. Each year, insects destroy about 25 percent of food crops worldwide. many transgenic plant with insect resistantance have been developed by adopting gene transfer methods.

6. The gene helps the plants produce proteins that are toxic to certain insects They reduced the use of chemical pesticides in agriculture The genetically modified crops is called Bt-crops, because the insect-killing gene in the plant comes from the bacteria  Bacillus thuringiensis . This gene encodes a protein(cry toxin),that is toxic to many insects.

7. This bacterium is only weakly toxic to insects as a vegetative cell,but during sporulation.it produces an intracellular toxic protein crystal.the parasporal body, that can act as a microbial insecticide for specific insect groups [Lepidoptera( moths,butterflies ), Diptera (flies and mosquitoes) etc].

8. The parasporal crystal,after exposure to alkaline conditions in the insect hindgut,fragments to release the protoxin . After it react with a protease enzyme,the active toxin is produced. Six of the active toxin units integrate into the plasma membrane to form a hexagonal shaped pore through out the mid gut cell.

9. This leads to the loss of osmotic balance and ATP and finally to cell lysis . The insect resistant genetically modified crops are produced by inserting the Bt gene(cry gene) from Bacillus thuringiensis into a crop through genetic engineering techniques and get the gene expressed.

10. Such plants can produce the toxic crystal protein and protect themselves from insects without any external application of pesticides. Bt GM crops are protected specifically against cotton boll worm ,pink bollworm, colorado potato beetle,European corn borer,tobacco bud worm etc.

11. EXAMPLES OF Bt CROPS Bt cotton Bt Brinjal Bt corn Bt potato

12. GOLDEN RICE In 2000,Ingo Potrykus (Swiss Federal Institute of Technology)and Peter Beyer (University of Freiburg),created “GOLDEN RICE” - a trasgenic rice capable of producing beta carotene , a precursor of vitamin A in the edible part of rice,endosperm , by using recombinant DNA technology. Deficiency of this vitamin cause night blindness.

13. The research was conducted with the aim of producing a fortified food to be grown and consumed in areas with a shortage of dietary vitamin A. Golden rice was created by transforming rice by the addition of 2 beta carotene biosynthesis genes 1 . 2 Daffodil genes ( Narcissus pseudonarcissus ) - psy ( phytoene synthase & phytoene desaturase ) and 2. 1 bacterial gene - crt 1 ( Lycopene beta cyclase ) from the soil bacterium Erwinia uredovora .

14. The psy and crt 1 genes were transferred into the rice nuclear genome and placed under the control of an endosperm specific promoter. Hence they are expressed only in the endosperm. The presence of beta carotene in the rice endosperm gives a characteristic yellow or orange colour to the rice and hence the name “GOLDEN RICE”.

15. The orginal golden rice was called SGR1 In 2005,a new genetically modified strain of Golden rice called Golden rice 2, which is capable of producing 23 times more beta carotene than the orginal variety,was produced by combining the phytoene synthase gene from maize with crt1 gene from the orginal Golden rice (Biotechnology Company,Syngenta,U.K )

16. BIOSYNTHESIS Biosynthetic pathway of provitamin A is a continuation of Lycopene pathway The starting point of this pathway is the production of GGDP ( Geranyl Geranyl Di Phosphate) Immature rice endosperm is capable of synthesizing GGDP but subsequent stages not expressed in tissues.

17. Early transformation with phytoene synthase gene to rice endosperm, specific promoter indicated that phytoene could be synthesized from GGDP in the rice grain.( phytoene is the precursor of beta carotene) The phytoene is converted into lycopene by phytoene desaturase . This lycopene is converted to beta carotene by using lycopene beta cyclase .

18. Flavr Savr Tomato

19. Flavr Savr Tomato Flavr Savr Tomato (also known as CGN-89564-2) is a genetically modified tomato with slow ripening and improved shelf life,produced by Calgene Company, California(1992). It is the first commercially grown genetically engineered food to be granted a license for human consumption.

20. Fruit softening is promoted by an enzyme Polygalactouronase (PG). It degrades pectin In the transgenic Flvr Savr Tomato,the gene that synthesizes Polygalactouronase is blocked and thus prevented it from softening,while still allowing the tomato to retain its natural colour and flavour .

21. Antisense RNA technology used to develop Flavr Savr tomato. Antisense RNA is a single stranded RNA that is complementary to a messenger RNA(mRNA). The novel variety was developed by insertion of an additional copy of the polygalactouronase encoding gene in the antisense orientation, resulting in reduced translation of the PG messenger RNA.

22. The PG enzyme is the chief mechanism of pectin degradation in tomato fruit leading to fruit softening. The transgenic variety ripens normally but experiences less pectin breakdown and, therefore, has increased thickness and consistency that benefits all stages of harvesting and processing.

23. Development of the Modified Plant The FLAVR SAVR™ tomato was created by  Agrobacterium -mediated transformation in which the transfer-DNA (T-DNA) contained a copy of the tomato PG encoding gene in the antisense orientation. In addition, the T-DNA contained sequences encoding the enzyme neomycin phosphotransferase II (NPTII). The expression of NPTII activity was used as a selectable trait to screen transformed plants for the presence of the antisense-PG gene.

24. Transcription of the antisense-PG gene did not result in the expression of any novel protein. The antisense PG gene is essentially a reverse copy of part of the native tomato PG gene that supresses the expression of endogenous PG enzyme prior to the onset of fruit ripening. The mechanism of decreased PG activity in FLAVR SAVR™ tomato is likely linked to the hybridization of antisense and sense mRNA transcripts, resulting in a decreased amount of free positive sense mRNA available for protein translation.

25. Reduced PG expression decreases the break down of pectin and leads to fruit with slowed cell wall breakdown,and delayed softening.