agri revision gm

agri revision gm - Genetic Modification of plants I...

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Genetic Modification of plants I Agrobacterium tumerfaciens: has a natural ability to genetically engineer plants introduces t-DNA into plant genome (transformation) – new piece of DNA added (lots of info) in nature it exploits plant to make food for itself only has to insert genetic info once because then induces a tumour – cells divide rapidly and these cells produce opine which it uses as a source of C. N and energy – plant/other bacteria don’t use opines so all for agrobacterium in nature it swims towards wounded and enters – PENETRATION The TRANFORMATION but only once cell so creates proteins. For a tumour you need 3 x the amount of auxin to cytokinin interesting the these genes are designed to work in plants and would not work in agrobacterium itself How we use this for GM: agrobacterium can do this because it contains an extra-chromosomal piece of DNA – the Ti plasmid it is very large (10% cell’s genetic info) and present on one copy – it contains a number of genes which can be put in 3 groups 1. T-DNA area – genes that encode proteins responsible for auxin and cytokinin biosynthesis to make tumours and for synthesis of opines (opine anabolism) 2. Virulence genes – genes responsible for invasion of agrobacterium e.g. detecting wound in plants. Also genes for transformation 3. opine catabolic gene so agrobacterium can digest opines BUT we don’t want tumours and opines – disarmed Ti plasmid with all genes for virulence but not t-DNA We add a small plasmid from E.coli which replicates in agrobacterium and contains engineered t- DNA (i.e. no auxin production genes anymore). It is binary plant transformation vector or a shuttle vector as it can replicate in 2 diff organisms (E.coli and agrobacterium) This means bacteria can still invade and transform cell – the changed t-DNA still has all the border genes so it knows where to cut and insert but all the stuff in between to be inserted is artificial Has to be done this way as Ti plasmid is too big to be engineered The cell still contains its chromosome, untouched Typical binary vector for plant transformation: in between border genes – where to cut and insert etc will be new gene of interest and also marker to check if gene has been added correctly these are usually things such as Ampiciline and Kanamycin resistance Infection and transformation n the laboratory: Grow plant in axenic culture – sterile. This is because agar culture is also suited to micro- organism that would outgrow plant. Also easy to grow. Transgenic plants should not be allowed into env whilst at this stage and also can just take a cutting and put on agar and will develop into a new plant axenic culture – wash seeds with thick bleach for 30mins, grow in vitro Cut “wounds” in leaves – take small sections of a leaf and put in… medium containing A-bacteria which penetrates and transforms cell 92days later some will have
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This note was uploaded on 02/22/2012 for the course AG 3306 taught by Professor Staff during the Fall '11 term at Texas State.

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agri revision gm - Genetic Modification of plants I...

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