Genetically Modified Organisms Tobacco plant with firefly gene © Keith Wood (of DeLuca lab) for Science Magazine 1986

Bt Maize  Bacillus thuringiensis produces a bacterial toxin (Delta-endotoxin)  The bacterium has been used as an insecticide since 1938  It stops the insect from feeding by attacking the insect gut lining Image Credit: Bacillus thuringiensis Bacillus thuringiensis © 2010 Paul Billiet ODWSODWS

Cry gene  The toxin is produced by the Cry gene  Found on plasmids in the bacterium  The gene is added to the genomes of crop plants using a bacterium that forms root nodules in plants (Agrobacterium tumificiens)  Bt crops produced from 1996 onwards: maize, potato, cotton, soybean © 2010 Paul Billiet ODWSODWS Image Credit: GMO Compass BT Maize BT Maize

Advantages  Only insects attacking the crop will be poisoned Environmentally friendly  All tissues are protected even the roots  Biodegradable – does not accumulate in the food chain © 2010 Paul Billiet ODWSODWS

Disadvantages  Pollinators may be killed too  Pesticide resistance in insects is rapid – but crop management could limit this  Pollen grains could spread the gene to wild relatives of the crop plant – but terminator genes could prevent this - but terminator genes considered unethical in developing nations  Technology expensive © 2010 Paul Billiet ODWSODWS

Spider silk  Spider’s silk is 5 times stronger than a thread of steel of the same thickness 3 times stronger than Kevlar (carbon fibre)  Spiders are carnivores and cannot be raised  Transgenic animals can produce the spider protein Aculepeira ceropegia a European orbweb spider © P. Billiet © 2010 Paul Billiet ODWSODWS

Spider silk  The gene for spider silk protein was isolated from the golden orb weaver (Nephila clavipes)  Not easy, it is a fibrous protein so it has a very repetitive gene sequence Nephila clavipes © C. Frank StarmerC. Frank Starmer © 2010 Paul Billiet ODWSODWS

Web-based kid  Gene (plus regulator genes) inserted into goat mammary gland cells  Genetically transformed cells could be made to secrete spider silk protein  Transformed goat cells fused to enucleated oocyte  Genetically transformed goat embryos produced Spider goat © Sean O'Neill © 2010 Paul Billiet ODWSODWS

 Goat grows up, females produce spider silk protein in their milk  Silk protein purified  Extruded through nozzle to produce silken thread  Not easy as the conditions are not quite the same a spider’s spinneret  Transformed goats can be bred together perpetuating the trait © 2010 Paul Billiet ODWSODWS

Applications  Super strong surgery thread  Artificial ligaments  Light bullet proof body armour  Biodegradable fishing line © 2010 Paul Billiet ODWSODWS