transgenic crops

agronomic traits that are targets of plant biotech

yield, herbicide resistance, pest/dissease resistance, abiotic stress resistance, reproduction

quality traits that are targets of plant biotech

processing, shelf life, nutritional quality, reduced anti-nutritionals

glyphosate function

herbicide which acts by inhibiting a chloroplast enzyme (EPSP synthase) required for aromatic amino acid synthesis

how is biotech used for herbicide tolerance

mutant EPSP synthase gene (shkG) was isolated from a bacterium resistant to the herbicide and introduced to plants for glyphosate resistance

pros of herbicide tolerance

enhanced crop productivity - reduces soil erosion, fuel costs and GHG emissions

cons of herbicide tolerance

possible reduction in biodiversity

bacillus thuringiensis

Bt - soil bacterium whose spores contain a crystalline protein that kills insects - toxin is encoded by cry genes

how is Bt used for insect resistance

toxin is very specific and only binds to receptors in gut of target insect - constructs with different cry genes have been introduced to plants

Bt pros

reduced costs due to less pesticide use, reduced environmental impacts, improved farmer health, improved food quality as less fungal toxins

Bt cons

selection pressure for resistant pests, possible effect on non target insects like pollinators

how does Bt work to kill pests

larva consumes toxin - crystals solubilised and toxin activated by proteolytic cleavage in midgut - toxin binds to specific receptors - binding triggers cells death in midgut - larva dies from septicaemia

golden rice

provitamin A enriched rice variety

vitamin a =

eye pigment = retinol

retinolic acid =

growth hormone

provitamin a =

beta-carotene

symptoms of vitamin a deficiency

night blindness, xerophthalmia, increased susceptibility to death

how can transgenic golden rice be made

2 daffodil genes introduced to erwinia gene under control of endosperm-specific promoters - enhances the B-carotene

pros of golden rice

contains 50% of a childs RDA of vitamin A- potential to save millions of children from death/blindness

cons of golden rice

reinforces dependence on rice diet, better to increase diet diversity

anthocyanins

good antioxidants which provide colour in red cabbage, blueberries etc

how do arctic apples/innate potatoes reduce bruising

they have reduced polyphenol oxidase - reduces browning

innate potatoes have reduced .. levels?

asparagine - this is converted to acrylamide (carcinogen) at high temps

process of transient expression of novel products using virus vectors:

growth of plants from seed - growth of agrobacterium with construct - plant leaves infiltrated - protein expressed in leaves

leaves harvested - protein extracted and purified

how does gene editing with CRISPR-cas9 work?

there is short guide RNA and an enzyme to cut DNA - guide RNAs added to target genes of interest - random repair errors introduce mutations - can engineer specific sequence changes