Light Signal Transmission Flashcards
Where does phyBPfr localise?
Nuclear Bodies
Co-loc WITH PIF
What is “Fluence Rate”?
Light intensity
How is PhyBPfr localisation Fluence Rate Dependent?
Low Pfr level - diffuse, many small
High Pfr level - many large foci
More Pfr = PhyB action =
suppress HYP
What are PIFs?
TFs that interact with PHY
From bHLH family
PIF 1, 3, 4 + 5
What are the 2 domains of PIF?
APB - Active PhyB Binding
bHLH - Bind DNA
(promoter cis elements)
can bind to other PIFs
(Heterodimer)
What cis elements to bHLH domains often bind to?
G box
CAC GTG
How does PHY try to (-) regulate PIFs?
- Sequester + prevent promoter binding
- Trigger their Phosphorylation
(So they are degraded by E3 Ligase Deg)
How does E3 Ligase Mediated Deg work (with PIF?)
E3L has F-Box protein
This recognises PIF + adds U
E1 carrier gives U to E2
E2 cattier gives U to E3
E3 adds this TAG to protein
U chain is degradation target
Proteosome eats PIF (yum)
When are PIFs abundant? What happens?
In DARKNESS and low R:FR
(because low Pfr)
More PIF = ELOMGATION
What did ChIP-Seq experiments show about PIF5?
Hornitschek et al, 2012
They bind to G-BOXES
Binding loci had at least 1
G-Box (55%) or
E-Box (a variant - 41%)
PIL 1 promoter strongly upregulated
What did PIL1-GUS expression analysis show?
PIL1 strongly UPREGULATED in FR environments
(PHY is OFF)
GUS staining lets us visualise where promoter is expressed
What are PIF4 + 5 known to control?
AUXIN Genes:
YUC 8
IAA 29
What does the Yucca 8 gene do?
In AUX biosynthesis pathway
Convert TRP-AUX intermediate
into AUXIN
How is Auxin regulated with PIFs?
Low R:FR = More Pr than Pfr
Less Pfr = More PIFs
Yucca 8 upregulated
= More Auxin!
How is Auxin regulated?
Aux/IIA represses ARF.
ARF represses Aux Synthesis.
Aux/IIA detected by
E3L protein TIR 1
E3 Ligase adds U -
Targeted for Deg
Aux Responsive Gene can start Auxin synthesis
