Plant physiology Flashcards
Why is Arabidopsis Thaliana a model organism?
1) Small
2) first diploid genome that has been completely sequenced
3) Rapid life cycle
4) short generation time
5)Prolific seed production and easy cultivation
6) easy to manipulate
7) Self-pollination (hermaphroditic)
what are the parts of a germinating seed?
cotyledon (mono or dicot), hypocotyl (initial stem) and root
what is etiolation?
Elongated, pale green to yellowish growth due to low light intensity or darkness, extended hypercotyl, unfolded cotyledon
what is a phytochrome?
a chemical photo-receptor in plants that is used to detect light, a photoreceptor to detect light, absorbs red and far-red light most strongly (600-750nm) as most useful for photosynthesis, can also absorb blue light (350-500nm) & UVA radiation
what are the parts of a phytochrome?
photosensor domain (contains chromophore phytochromobilin) and regulatory domain
what is photochromobilin?
a chromophore, sense if light is far red or red, converts between pr and pfr version (photoreversiblity), these are cis/trans isomers, pi bond
what happens to phytochrome in red light?
red goes to pr, causes cis/trans isomerisation, this changes protein structure so that NLS is exposed, it moves to nucleus, and changes gene expression, triggers germination
what is evidence for phytochrome changes?
GFP - in light
what is photo reversibility?
pr - inactive form (dark and far-red light), switches to pfr - active form (light and red light), shifts based on light, its an equilibrium, some in each form
what is phyA mutant?
plant has a mutated phytochrome so can’t detect light
- has a dark phenotype, looks etiolated, but could also be linked to whether it can isomerise and move to nucleus
when will seeds germinate?
in red light
- chlorophyll absorbs red light but can’t reach ground bc absorbed by higher trees so unproductive to germinate until a gap in trees otherwise only far-red light will reach ground which keeps phytochrome in pr inactive form, so will stay in cytosol and move to nucleus so won’t affect gene expression
What are circadian rhythms?
biological clock, respond to external factors to conserve energy, clock genes are activated and protein builds up, it is a negative feedback mechanism
what is the period?
time between peak to peak
what is the amplitude?
height from trough to peak
what is the phase?
specific point in a cycle
what is a northern blot?
Analyzes RNA fragments (mRNA) on a gel electrophoresis using a probe, tracks how fast genes switched on or off
how to identify clock components?
use reporter protein e.g luciferase, add a promoter used in the clock so can see when its active and then create mutants to track which proteins used and changed
what is entrainment?
the process of taking external signal and feeding it into biological system, if plant in dark, clock gets out of sync, each cell has a clock of its own
how does phytochrome entrain the clock?
it senses presence of light (dawn) and moves into nucleus, acts as a transcription factors, if no light then doesn’t happen and gets out of sync
