The epidermis Flashcards
What is the epidermis?
The one cell thick layer around the organs of the plant (the skin)
What are the three cell types of the epidermis?
- Pavement cells
- Stomatal guard cells
- Trichomes
What are the cell types of the root epidermis?
Hair cells and non-hair cells
What three types of trichome mutants can you look at to find out about WT gene function?
Trichomes mutant in
- Number
- Distrubution
- Morphology
How many genes have been linked to trichome development?
25
What two mutants have no trichromes?
GLABRA1 and TTG1
What does the WT GL1 gene encode?
A transcription factor
What does TTG1 encode?
a protein that binds to GL1 and activates it
What is the phenotype of the mutant in GLABRA3?
Fewer trichomes than the WT
What does GL3 gene encode?
A transcription factor that forms a protein complex with the GL1 transcription factor and the TTG1 protein
What is the function of of the GL1/GL3/TTG1 complex?
It regulates genes involved in trichome development
What kind of pathway is the GL1/3/TTG1 complex involved in?
A positive regulatory pathway as it PROMOTES trichome development
Why are trichomes evenly distrubuted if its a random process?
They cell that turns into a trichome produces a negative signal to the cells around it to stop them becoming trichomes
How could you find genes that are involved in the spatial distrubutuion of trichomes?
Look for mutants with clusters of trichomes where the gene is obviously defective
What two mutants have clusters of trichome and therefore are defective the genes that allow the trichome producing cell to give off negative signals to the cell around it?
Triptycon and caprice
What are the wildtype triptycon (TRY) and caprice (CPC)
Transcription factors that are involved in a negative regulatory pathway
What is the phenotype of mutants overexpressing TRY and CPC?
No trichomes
What is the phenotype of a dis (distored) mutant?
Normal number and spacing of trichome but have a deformed morphology
What is the phenotype of a mutant in GL1 and DIS1?
No trichomes
What does the fact a GL1/DIS1 double mutant shows no trichomes instead of deformed morphology of show?
That gl1 is epistatic to dis1 (it predominates)
What does the GL1/DIS1 mutant tell you about the pathway in which the genes are expressed?
That GL1 must be expressed upstream of DIS1 so therefore cell commitment to making trichome comes before their morphology
What are Arp2/3 proteins required for/
Normal actin filament production
What is the phenotype of the too many mouth mutants (tmm)
Clusters of stomata
What does the tmm mutants tell you about the function of the WT gene?
It is involved in spatial distrubutuion of the stomata
What is it about the tmm mutants that tells you that trichome and stomatal development are not linked?
The tmm mutants has too many stomata but normal spacing of trichomes so you can see they are controlled independently
What is different about the formation of root hairs are compared to trichomes and stomata?
Whether a root hair forms ins position dependent
What decides where a root hair forms?
The cell that is in the junction between two cortical cells will become a root hair cell
What is ectopic root hair production?
When cells that were not supposed to become hair cells become them
What can the weerwolf mutant tell you about the WT function of the gene?
It is involved in specifying non-hair cell fate rather than specifying hair cell fate
Apart from wer1 what other mutant shows ectopic root hair formation?
TTG1 (involved in trichome commitment)
How do wer1 and ttg1 function together to specify non-hair cell fate?
They repress the action of adjacent cells to stay as a non-hair cells and causes it to be a hair cell
