Plant Physiology I

Frage	Antworten
Problems w/ crop research	Big plants Long generation times Often complex genomes Difficult to genetically manipulate
Arabidopsis thaliana	Small short generation time small genome easy to genetically manipulate
Germination	Requires water, O2, light Cotyledon Hypocotyl root
Etiolated plant	If seed germinates and doesn't detect light Extended hypocotyl Cotyledons don't unfold Seedling still thinks it's underground, seed reserve runs out
Phytochrome	Photoreceptor Abrobs red and far-red light(600-750nm) Can also absorb blue light (350-500nm) and UV-A (320nm-400nm)
Phytochrome structure	N-terminal Phytochromobillin Photosensory domain Regulatory domain C-terminal
Phytochromobillin	Chromophore Red light=Pfr (active) Far red light=Pr (inactive/dark)
Phytochrome overview	Pr converted to Pfr by red light Induces conformation change Translocates to nucleus from cytosol influences gene expression Germination initiated
PhyA mutant	Plants w/ knockout PHYA (phytochrome) can't detect light Look etiolated Proof that phytochromes have a key role in light sensing
Differing light quality	Light available at canopy Not at understory seedlings wait until gap in canopy to start germinating
Why living on a rotating planet is biologically stressful	Large variation in enviro conditions including: 'C/L.I./humidity
Circadian clocks	Biological oscillators w/ ~24hr period
What defines a circadian rhythm?	Three parameters: Period - time between comparable points Amplitude-height btw. peak+troughs Phase-any point in cycle that's distinct
Clock mechanism	Night: Gene 2 is active, producing 2 protein. Dawn: Accumulation of 2 until it reaches a level where it activates expression from gene X and gene Y. Day: X and Y protein accumulate. Inhibit expression of gene 2. NEGATIVE FEEDBACK LOOP.
Requirements for identifying clock components	Luciferase - luminescent reporter protein from fireflies Promoter crontolled by clock
Method	Put promoter controlled by clock in front of gene you think responds to clock effect.
Reporter complex	Look at luciferase expression through a microscope, pulsing of luciferase in fluorescent dye Randomly mutate plant and look l ook at changes circadian oscillations
Temperature compensated	Circadian clock runs at same speed regardless of temperature Subject to physics, each step will run faster as temp ^, however responses will compensate each other i.e. ^rate of synthesis = ^rate of degradation
Entrainment	In constant darkness clock begins to run out of sync In natural conditions clock checks the natural environment to 'reset' itself This is called entrainment
What entrains the clock in plants?	Phytochrome
Components of the circadian clock	Central oscillator - a -FDBCK loop Input for entrainment to local conditions - phytochrome Output to effect responses - alter gene expession

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