Hello Friends
Topic of discussion is Agrobacterium tumifaciens
It is gram negative bacteria.
The agrobacterium causes crown gall disease and hairy root syndrome.
A. tumifaciens causes crown gall and A. rhizogenes causes hairy root syndrome.
The bacteria enter plant through cuts and wounds.
Most of these bacteria have plasmids. The size of plasmid is variable and the ability to synthesize the opines and virulence is plasmid borne traits.
This plasmid is called the Ti plasmid.
Only a segment (which is called t DNA) of this plasmid enters the plant on infection and integrated into host genome at non specific site.
The ends of tDNA are specialised as they are flanked by 25 bp repeats called as border sequence.
These border sequence are involved in tDNA transfer but they themselves do no get transffered.
The genes which regulate the trasfer of tDNA are present at some other sites in plasmid DNA and are called vir genes.
vir A and vir G are important and constituvely expressed and their product are required for expression of other vir genes.
vir A product is a protein kinase.
The wounded plant also secrete acetosyringone for vir gene expression.
vir G product is soluble protein which is phosphorylated by vir A product.
vir G product is transcription factor required for activation of rest of vir genes.
vir B produces component of pilus.
virD1 encodes for endonuclease which act on border sequence to create nicks and initiate transfer of tDNA.
vir D2 remain attached to processed DNA.
vir C1 and C2 product act on enhancer sequence.
vir E codes a DNA binding protein which provide stability to DNA.The processed DNA is called "Fire Cracker Complex".
The vir D2 product are attached to processed tDNA and protect this DNA from host nucleases.
vir D2 protein also has nuclear localising signal and are required for recombination evennts.
The cell in which tDNA enters have high level of phytohormones, the genes called tms1 and tms2 synthesize auxin, tmr synthesize cytokinin, ocs synthesize octopine and nos synthesize nopaline.
This tDNA is also used as vector by removing tms1, tms2 and tmr region.
It is even used to express in eukaryotic system as promoter sequence and polyadenylation sites of tDNA are very similar to eukaryotic system.
Many monocots are not infected by this bacteria as they do not sectrete acetosyringone.
Hope this will help you all. See you all with next topic.
Thnkyou for reading.
Topic of discussion is Agrobacterium tumifaciens
It is gram negative bacteria.
The agrobacterium causes crown gall disease and hairy root syndrome.
A. tumifaciens causes crown gall and A. rhizogenes causes hairy root syndrome.
The bacteria enter plant through cuts and wounds.
Most of these bacteria have plasmids. The size of plasmid is variable and the ability to synthesize the opines and virulence is plasmid borne traits.
This plasmid is called the Ti plasmid.
Only a segment (which is called t DNA) of this plasmid enters the plant on infection and integrated into host genome at non specific site.
The ends of tDNA are specialised as they are flanked by 25 bp repeats called as border sequence.
These border sequence are involved in tDNA transfer but they themselves do no get transffered.
The genes which regulate the trasfer of tDNA are present at some other sites in plasmid DNA and are called vir genes.
vir A and vir G are important and constituvely expressed and their product are required for expression of other vir genes.
vir A product is a protein kinase.
The wounded plant also secrete acetosyringone for vir gene expression.
vir G product is soluble protein which is phosphorylated by vir A product.
vir G product is transcription factor required for activation of rest of vir genes.
vir B produces component of pilus.
virD1 encodes for endonuclease which act on border sequence to create nicks and initiate transfer of tDNA.
vir D2 remain attached to processed DNA.
vir C1 and C2 product act on enhancer sequence.
vir E codes a DNA binding protein which provide stability to DNA.The processed DNA is called "Fire Cracker Complex".
The vir D2 product are attached to processed tDNA and protect this DNA from host nucleases.
vir D2 protein also has nuclear localising signal and are required for recombination evennts.
The cell in which tDNA enters have high level of phytohormones, the genes called tms1 and tms2 synthesize auxin, tmr synthesize cytokinin, ocs synthesize octopine and nos synthesize nopaline.
This tDNA is also used as vector by removing tms1, tms2 and tmr region.
It is even used to express in eukaryotic system as promoter sequence and polyadenylation sites of tDNA are very similar to eukaryotic system.
Many monocots are not infected by this bacteria as they do not sectrete acetosyringone.
Hope this will help you all. See you all with next topic.
Thnkyou for reading.
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