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How transgenic plants are made

How transgenic plants are made. Original approach used a natural plant system Current plasmid based with various delivery systems Currently many traits engineered or under development Now augmented by newer high throughput genome sequencing techniques

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How transgenic plants are made

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  1. How transgenic plants are made • Original approach used a natural plant system • Current plasmid based with various delivery systems • Currently many traits engineered or under development • Now augmented by newer high throughput genome sequencing techniques • Highly politicized, especially in EU

  2. Agrobacterium causes crown galls In the field …and in the lab

  3. A plasmid transfers DNA to the plant

  4. Used to make transgenic plants in 1983

  5. Only small part of plasmid is transferred Transferred DNA ~30 KB Growth factor stimulates gall growth in plant Transfer region controls excision and integration of DNA into plant host Direct repeats 200 KB

  6. Transferring new genes to plant cells EXCISION SITES KanR Antibiotic resistance genes included KanR INTO PLANT GENOME KanR

  7. Two classes of plants require different methods MONOCOTS Electroporation DICOTS Agrobacterium Soy Cotton Aubergine Yams Tomato Potato Corn Rice Wheat

  8. SOME ORIGINAL TRANSGENIC CROPS

  9. WHAT GENES ARE TRANSFERRED INTO PLANTS? • HERBICIDE RESISTANCE • DROUGHT RESISTANCE • SALT RESISTANCE • INHIBITORS OF RIPENING • NUTRITIONAL SUPPLEMENTS • PHARMACEUTICALS • INCREASED HEAVY METAL UPTAKE

  10. Bacillus thuringenensis (Bt) - Insect Resistance • SPORE FORMING BACTERIA • SAME AS B. anthracisAND B. cereus • PLASMIDS ONLY DISTINGUISH • PLASMIDS PRODUCE CRYSTALS OF CRYPROTEINS • MANY DIFFERENT KINDS OF CRY • SMALL PROTEIN = EASY MOLECULAR METHODS • MOST Bt HAVE SEVERAL TOXINS • TOXIC TO DIFFERENT INSECTS

  11. LONG HISTORY IN ORGANIC AGRICULTURE

  12. ONE Bt TOXIN STRUCTURE BINDS SPECIFICALLY TO A RECEPTOR INSERTS INTO GUT WALL PROTECTS THE PEPTIDE FROM DEGRADATION

  13. NO TOXIN TOXIN Bt proteins dissolve the insect gut lining TOXIN BINDS TO SPECIFIC RECEPTORS IN GUT WALL PROTEIN CLEAVED DISSOLVES GUT LINING

  14. Huge Diversity of Different Proteins SIMILAR MODES OF ACTION DIFFERENT INSECT SPECIFICITIES

  15. Bt CRYSTAL PROTEINS AND THEIR TARGET SPECIES

  16. MANY Bt-RICE VARIETIES HAVE BEEN MADE

  17. CHANGES IN GUT PROTEIN CAN MEDIATE RESISTANCE

  18. DIFFERENT TRANSGENIC GOAL – ADD NUTRIENTS • POLISHED RICE IS MAINLY CARBOHYDRATE • STAPLE FOOD IN AREAS WHERE VITAMIN • DEFICIENCIES ARE COMMON • ADD VITAMIN A TO RICE ENDOSPERM? • RICE HAS ENZYMES TO MAKE VITAMIN A PRECURSOR

  19. LIMIT IN NORMAL RICE CONVERT GGPP INTO CAROTENEWITH GENES FROM OTHER PLANTS DAFFODIL ERWINIA DAFFODIL

  20. RECENT DEVELOPMENTS • SIMPLER TRANSFORMATION • SURVEY OF PSY GENES SHOWED • MAIZE GENE MOST ACTIVE • PROTOTYPE OF PRODUCING OTHER COMPLEX MOLECULES IN EASY-TO-CULTURE PLANTS

  21. Herbicide Resistance - most common in US • Glyphosate = Roundup • Inhibits an enzyme needed to synthesize aromatic amino acids ( Phe, Tyr and Trp) • Roundup ready plants carry a bacterial version of the enzyme that is naturally resistant to Roundup • Animals do not have this system, so not toxic to humans • Resistance can evolve in a variety of ways in plants exposed to Roundup

  22. Diverse Methods & Goals, Many Controversies

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