Phytochromes Flashcards
What TWO light receptors affect PHOTOMORPHOGENESIS?
Cryptochromes (Blue)
Phytochromes (Red/FRed)
Why is seed germination R/FR reversible?
Germination depends on LAST light treatment
Grow if R
How is R/FR reversibility lost?
Longer DARKNESS hours from (grow) R to (antigrow) FR leads to MORE growing
Especially from 6h (below 10%)
to 9h (around 75%) and up
(Max around 80%)
( ! ) What What does PHOTOMORPHOGENESIS include?
- Change of form
- Germination
- Stem height + thicc
- Lefa expansion
- Flowering
What effects does light have to de-etiolate seedlings?
Hypocotyl STOP elongating
LEAVES unfold, expand and green
What does a PhyA mutant look like?
Wild Type
What does a PhyB mutant look like?
Long Petioles
Small Leaves
Root Hairs
Which PHY mediate suppression elongation?
A, D + E
Which PHY regulate compact rosette phenotype?
A, B and E
Which PHY is the predominant modulator of de-etiolation?
Phy B
Are there roles for Phy A in de-etiolation?
Yes! They are normally masked by PhyB
PhyAB mutants have slightly longer Hyp than PhyB mutants
Which photoreceptors modulate light-activated CHLOROPHYLL SYNTHESIS
PhyA, PhyB, Cry1, Cry2
Act thru regulation of HEMA 1
(Gene That encodes glutamyl tRNA Reductase)
How does PhyB relate to PhyD?
PhyD has MINOR role in de-etio
Accessory roles to PhyB in HYP elongation
PhyB + D have HIGH seq similarity
(surprisingly)
PhyBD mutant HYP longer -
SYNERGISTIC EFFECT
How does PhyB relate to PhyC?
PhyC mutants have long HYP
PhyBC mutants do NOT
PhyC operates via PhyB -
Obligate Heterodimerisation of C
What is the structure of PHY (4 domains)?
~ A DIMER!! ~
GAF - binds chromophore
PAS 1 + 2 -
Bind DNA & Proteins
Nuclear Loc Signal
HKRD - His Kinase Related Domain
