Light Control Flashcards
What info does light provide?
Seasons
(Day length/int)
Time of day
(intensity)
Local Habitat
(Vegetation proximity)
What limits light availability?
Time of Year
Time of Day
Latitude
Cloud cover
(reduce 3-6x)
What has EdUni’s Geosciences weather station found?
Max solar radiation in July
Lowest in January
Correlation with temperature
No correlation with rain
Why does light intensity vary during the day?
Intensity decreases as ANGLE of incidence decreases
( ! ) What are the 5 Physiological Responses to Low Light Intensity?
- Longer INTERNODES + STEM
- Larger LEAF SA
- Thinner LEAF AND STEM
- Thinner CUTICLE
- ONE layer of palisade cells
(Below epiderm, have chloroplasts)
What range of light can plants sense?
UV to Far Red
( ! ) has What FOUR things do Phototropins do?
- Phototrophic growth (duh)
- Stomata opening
- Leaf expansion
- Chloroplast movement
accum at top - Low
hide at sides (protect) - High
retreat to bottom - Darkness
What did Briggs and Liscum identify?
Briggs - A blue-activated mem-bound protein (‘90s)
Liscum - nph1 mutant; map to PHOT1 Locus
What are Phototropins?
Serine/Threonine KINASES
PHOT1 and PHOT2
What domains to Phototropins have?
- PHOTOSENSORY domain
2. OUTPUT domain
What does the Phot PHOTOSENSORY domain do?
LOV 1 + 2 domains:
bind (flavin-based) FMN chromophores
(FMN 2 more active)
Ja is flexible alpha helix
What does the Phot OUTPUT DOMAIN do?
Has Ser/Thr Kinase
Enzyme activity (signalling)
Subcellular localisation
What does Blue Light promote in a Phot receptor?
A covalent cysteine bond
Active form - cannot absorb BLUE
What happens with activation/repression of the Phot protein?
Dark: PS and Kinase domains together
Blue: Ja Helix unfolds
Autophos by ATP
What changes with Phot active conformation change?
- SIGNALLING activation
- RELOCATION:
PHOT1 @ cyto
PHOT2 @ golgi
(Plas Mem in Dark)
( ! ) What FOUR things do Cryptochromes regulate?
- De-etiolation
- Stomata opening
- Plastid Development
- Flowering Time
What did Margaret Ahmad discover?
the cry1 mutant -
discover CRY struc/func
What are Cryptochromes?
CRY 1 + 2 + 3
All resemble photolyases
(DNA Repair Enzyme)
CRY 3 has this function
(Operates in CP/Mito)
What domains to CRY 1 + 2 have?
- Photolyase Homo Region
(PHR) Domain
binds 2 DIFFERENT chromophores
(MTHF And FAD)
- C-term extension
(CCE) Domain
What do the chromphores binding to the PHR domain do? (CRY)
FAD is main receptor
MTHF absorbs UV and transfers energy to FAD
How is CRY activated?
Blue induces neutral FAD RADICAL to form:
> FADH <
(Resting, oxidised form of FAD absorbs blue)
What happens to the CRY protein upon activation?
A DIMER forms
(Two PHR domains together)
CCE bits OPEN
(Signalling takes place)
Where does CRY accumulate when blue activates it?
I’m NUCLEAR BODIES
(many smol > few large)
CRY2 is light LABILE
