Hormones Flashcards
Why is the MAPK cascade effect necessary?
To amplify effect of hormone. If this did not occur, it would simply get diluted in the cytosol.
What is the role of MAPK in animals vs plants?
In animals, has mainly mitogenic effects - growth. In plants it is much more broad.
What is the MAPK cascade?
Series of phosphorylation and dephosphorylation reactions with the gamma phosphate from MAPK3 to MAPK1 increasing in magnitude each time.
Where are plant receptors placed?
Can be internal or external
What is autocrine and paracrine?
Auto - self the hormone is synthesised in the same cell that recieves it. Para - hormone generated in other area of plant.
Describe hormone pathway
Environmental or programmed trigger Synthesis of hormone Transport to action site Hits receptor - signal transduction response until threshold is hit breakdown process by catabolism or put in vacuole
Effect of ABA on stomata?
Results in closure (regulated by drought stress)
How are plant hormones different to animal signal transduction pathways?
They are usually degrading repressor proteins so they cut the rope and goes faster like a horse on a rope. QUICKER RESPONSE
Describe the ubiquitin degredation pathway
Ubiquition activated by phosphorylation passed on to three proteins (E1, E2, E3). Target protein then ubiquitinated to act as signal for degradation. Done by 26S proteosome.
How many combos of these E proteins exist and why is this important?
2400 must be specific for each protein
Where is auxin active
At the tip of growth
How does addition of auxin result in a change of gene expression?
Genes are constantly bound to auxin response factors (transcription factors). But in turn these tfs are being repressed by IAA/AUX. These IAA repressors have active site that is specific to auxin and results int he release of the tf and hence transcription.
This bound auxin molecule then forms an E3 ligase complex which results in degradation of auxin.
This acts as a negative regulator and means the repressor will be activated again.
Example of membrane bound receptor?
Brassinosteroids.
Structure and process of brassinosteroid receptor?
Extracellular signal receptor recieves brass. Intracellular BRI1 and BAK1 become phosphorylated. This signals BSKs (signalling kinases) and MAPKs and goes to BIN2 and degrade its phosphate group.
Why is it useful to degrade phosphate group on BIN2?
Because under non brass conditions it would go on to pass through the nucleus and degrade tfs. Since this is not happening tfs can build up and result in transcription of new genes. Negative repression
Explain green revolution
By Norman Boulaug
Between 1960s and 70s
Involved production of a semi dwarf increase grain yield variety
Saved 1 billion people from hunger
What causes the short wheat variety?
Gibberelins mutant in synthesis and response.
Describe gibberelic acid
Stimulates plant growth and development so stopping it makes a plant shorter.
Why are DELLA proteins called this and what is their role?
contains motif of amino acids: asp, glut, leu, leu, ala they are repressors of plant development
Where is gibberelins receptor located?
In the nucleus
What is the relationship between DELLA and GA?
DELLA inhibits seed growth/flower development, GA promotes this - they’re opposites.
How does DELLA repress these transcription factors?
Stopping their binding to DNA or actually degrading them.
What is the GA receptor called and how does this then promote growth?
GID1 undergoes N-Terminal conformational change in the presence of GA which then binds to repressor and releases the DNA to begin transcription.
How is the DELLA/GA complex changed in dwarf wheat?
Repressor is GA insensitive so constantly bound to DNA
What is the main limiting step in the production of ehtylene (that results in fruit ripening)?
Conversion of SAM to ACC
Two methods of reducing ethylene production in tomatoes?
Insert antisense gene to affect ACS gene. Sequester ACC
