Midterm 2 - Notes 6 (Part 2) Flashcards
Auxin
A positive regulator of cell division, cell elongation and vascular differentiation
Cytokinin
Positive regulator of cell division and cell differentiation
- most likely expanded by combined actions
What do plant growth hormones often act in?
Concert
- ratio of auxin and cytokinin: undifferentiated proliferation (callus), root formation or shoot formation
What other hormones are involved in via secondary effects?
Ethylene
What are elevated levels in transformed cells sufficient to do?
Induce tumour formation and vascularization of tumours
What did infected and axenic tumour tissues produce?
Amino acid conjugates that have not been found before in plants
- called opines
What is the composition of opines dependent on?
Agrostrain
- but not on plant host infected
Where does opine specifying information come from?
Bacterium
- alongside with the TIP
What is a carbon source for bacteria?
Opines
What are strains specific to? (2)
- What they can build
2. What they can break down
What do you typically not find in plants? And why?
Typically dont find octopine and nopaline
- because plants dont make them
Where can you find octopine and nopaline?
In tumours
- the strain is specific to which compound is being made
What happens if you remove anti-bacterium after initiation?
They continue produce because they are now cancerous
What are crown gall tumours introduced by?
A. tumefaciens
What must have been transferred to the plant?
TIP
What can virulence be transferred to?
Normally non virulent strains
Why was virulence lost?
When bacterial is grown at elevated temps
What does presence of a large plasmid correlate with? (3)
- Virulence
- Tumour formation
- Opine biosynthesis
- later called the tumour inducing or Ti-plasmid
Where was there more connection between?
The ability to affect the plant and the plasmid
- ability to transfer virulent from one with it to one that doesnt have it
What happens if you heat them up?
It doesnt kill them but it can be lost and so is virulence
What is necessary for infection?
Ti plasmid
- contains a tumour inducing principle
What is Ti plasmid responsible for?
Transfer of TIP produced elsewhere
What was being looked at in the DNA hybridization study?
If the plasmid from anti-bacterium is present in the eukaryotic cells
What were the steps in the DNA hybridization study? (6)
- Labelled single strands of plasmid DNA (radioactive labels)
- used hybridization - Mix with excess tumour DNA
- Denatures DNA at 100C
- allowed for it to denature and renature - Allow to re-associate at 65C
- labelled double strand only formed if cDNA present in target DNA - Separate single and double stranded DNA on hydroxyapatite columns
- would expect if the DNA is present that you would get dsDNA with the radioactive labelled strand - Count radioactivity in each fraction
What was used as a positive control in the DNA hybridization study?
Took labelled strand with on labelled strand and hybridized it with itself
What was used as a negative control in the DNA hybridization study?
Mixed Ti plasmid with plant DNA
Why was the DNA hybridization study not convincing?
Because the whole plasmid is not incorporated into plant tumour DNA
What did they discover in the DNA hybridization study?
3B was the only band that was present in plant DNA from tumours
What are some additional experiments that were being performed? (2)
- Genomic southern blots
- Recovery of T-DNA from genomic DNA of tumours
- ect…
What is the part of the plasmid that gets transferred?
T-DNA
