week 9

Question 1

why is light so important for plants

Answer 1

it helps regulate gene expression as 1/3 of genes in the genome are regulated by light in seedlings

Question 2

what enzyme is used to visualise changes in transcription and why

Answer 2

luciferase as it is unstable - beta-glucuronidase is too stable

Question 3

how is the CAB gene transcription visualised

Answer 3

1. CAB gene promoter introduced to a transgenic pant
2. add luciferin
3. monitor luciferase activity

Question 4

how does luciferase activity fluctate over a 24 hour period

Answer 4

rises and falls, as it peaks in the middle of the day then decreases to midnight, then increases again, these rhythms mimic a plants circadian rhythm

Question 5

how aspects of light do plants detect

Answer 5

lights presence or absence
light quantity
light spectral quality
light direction
light duration

Question 6

name regulatory receptors in plants for light

Answer 6

1.phytochromes - detect red and far red light
2.crytpochromes and phototropins - both detect UV-A and blue light
3.UV-B photoreceptor UVR8 -detects UV-B

Question 7

what are photoreceptor structures

Answer 7

the apoprotein is the photoreceptor protein and the chromophore is attached to the apoprotein
a chromophore is a small organic molecule that absorbs light
together they comprise the photoreceptor

Question 8

what forms do phytochromes exist in and where are they present

Answer 8

red (Pr) and far red (Pfr)
Pr is present in dark grown plants and illumination with red light produces Pfr
Pfr form of phytochrome initiates biological responses

Question 9

what is a cryptochrome and its role

Answer 9

bind flavin and pterin chromophores that absorb UV-A and blue light
involved in controlling processes such as stem extension, gene expression and flowering time

Question 10

what is a phototropin and its role

Answer 10

bind flavin chromophores that mainly absorb UV-A and blue light
control several important plant responses including phototropism