BLGY1211 Crop improvement and genetic engineering
Agrobacterium tumefaciens can transform plants
Natural ability to genetically engineer plants
Introduces T-DNA into the plant Genome (=transformation)
Causes Tumor formation (= cloning)
Forces plants to synthesize opines (= genetic engineering)
Uses opines as carbon and nitrogen source (= purposeful exploitation)
Crop pests (get examples)
Viruses
Bacteria
Fungi
Insects
Nematodes
Weeds
Slugs
Vertebrates
Natural openings of plants
The way to get inside for microbial pathogens
Stomata -transpiration
Lenticels -gas exchange
Hydrathodes -guttation
Lateral roots (easily damaged)
Wound sites (i.e. created by insect bites
Koch’s Postulates
Pathogen is always present in diseased tissue
Pathogen must be cultured pure on defined medium or in a susceptible host
Pathogen must be transmissible to healthy host and give same symptoms
Pathogen must be re-isolated from purposefully infected host and shown to be the
same as above
Braun’s hypothesis
It was possible to isolate tumours from Agrobacterium-infected plants that
continued to proliferate even in the absence of the bacterium.
The tumor inducing principle (TiP) could be DNA (1947)
Discovery that Agrobacterium-induced tumours produce opines, these are amino
acid derivatives (i.e. arginine condensed with α-ketoglutarate) that Agrobacterium
uses as food (carbon and nitrogen source), not normally found in healthy plants.
Key findings
Tumor inducing Agrobacterium strains had a giant extrachromosomal plasmid, not
found in non-pathogenic strains (Van Montagu’s lab 1974).
Establishment of the Tumor-inducing (Ti) plasmid
, Within a few years, it was shown that a portion of the Ti plasmid (the T-DNA) was
transferred to the plant cells and could be detected in tumours free of bacteria (at
the on-set of hybridization techniques).
Other important key-players were discovered via mutagenesis and more detailed
analysis.
Agrobacterium tumefaciens can transform plants
Agrobacterium tumfaciens virulence genes
How Agrobacterium infects and transforms plants in nature;
Agrobacterim is a soil bacterium that infects wounded parts of a plant the tumor
tissue produced opines and the Agrobacteria grow on the surface of the tumor
Agrobacterium genes
Natural Agrobacterium strains are not useful for biotechnology as we don’t want
cancer tissue and are not interested in opines
Agrobacterium tumefaciens can transform plants
Natural ability to genetically engineer plants
Introduces T-DNA into the plant Genome (=transformation)
Causes Tumor formation (= cloning)
Forces plants to synthesize opines (= genetic engineering)
Uses opines as carbon and nitrogen source (= purposeful exploitation)
Crop pests (get examples)
Viruses
Bacteria
Fungi
Insects
Nematodes
Weeds
Slugs
Vertebrates
Natural openings of plants
The way to get inside for microbial pathogens
Stomata -transpiration
Lenticels -gas exchange
Hydrathodes -guttation
Lateral roots (easily damaged)
Wound sites (i.e. created by insect bites
Koch’s Postulates
Pathogen is always present in diseased tissue
Pathogen must be cultured pure on defined medium or in a susceptible host
Pathogen must be transmissible to healthy host and give same symptoms
Pathogen must be re-isolated from purposefully infected host and shown to be the
same as above
Braun’s hypothesis
It was possible to isolate tumours from Agrobacterium-infected plants that
continued to proliferate even in the absence of the bacterium.
The tumor inducing principle (TiP) could be DNA (1947)
Discovery that Agrobacterium-induced tumours produce opines, these are amino
acid derivatives (i.e. arginine condensed with α-ketoglutarate) that Agrobacterium
uses as food (carbon and nitrogen source), not normally found in healthy plants.
Key findings
Tumor inducing Agrobacterium strains had a giant extrachromosomal plasmid, not
found in non-pathogenic strains (Van Montagu’s lab 1974).
Establishment of the Tumor-inducing (Ti) plasmid
, Within a few years, it was shown that a portion of the Ti plasmid (the T-DNA) was
transferred to the plant cells and could be detected in tumours free of bacteria (at
the on-set of hybridization techniques).
Other important key-players were discovered via mutagenesis and more detailed
analysis.
Agrobacterium tumefaciens can transform plants
Agrobacterium tumfaciens virulence genes
How Agrobacterium infects and transforms plants in nature;
Agrobacterim is a soil bacterium that infects wounded parts of a plant the tumor
tissue produced opines and the Agrobacteria grow on the surface of the tumor
Agrobacterium genes
Natural Agrobacterium strains are not useful for biotechnology as we don’t want
cancer tissue and are not interested in opines
