#Question id: 10462
#Unit 6. System Physiology – Plant
During an experiments mutating the conserved cysteine in the LOV1 domain of phot1 does not affect phototropic responsiveness (the seedlings bend toward blue light) whereas the equivalent mutation in LOV2 abolishes the response. What will be the conclusion has been drawn from this experiments?
a) LOV1 domain is secondarily responsible (primarily responsible is LOV2 domain) for kinase activation and LOV1 is not is coupled with the protein region Jα-helix that’s why it does not affect phototropic responsiveness
b) These studies have demonstrated that LOV2 domain is primarily responsible for kinase activation in response to blue light
c) This is due in part to the position of LOV2 within the phototropin molecule, where it is coupled to a protein region known as the Jα-helix
d) The function of LOV2 domain is thought to play a role in receptor dimerization by accomplishing the kinase activation in response to blue light
Which of the correct conclusion drawn from the above experiment?
#Question id: 10463
#Unit 6. System Physiology – Plant
LOV1 and LOV2, each binding a chromophore flavin mononucleotide (FMN), which one of the following statements shows incorrect prediction about LOV domains?
#Question id: 10464
#Unit 6. System Physiology – Plant
As with cryptochrome and phytochrome, the N-terminal photosensory region of the phototropins controls the activity of the C-terminal half of the protein, which contains a serine/threonine kinase domain. Following are some statements about photosensory region of the phototropins.
a) The activation of the C-terminal kinase domain then leads to receptor autophosphorylation on multiple serine residues that is required for all phototropin-mediated responses
b) In the dark, the N-terminal region, including the LOV domains, “cages” and inhibits the activity of the kinase domain
c) In the light, the N-terminal region, including the LOV domains, “cages” and inhibits the activity of the kinase domain
d) Absorption of blue photons by the LOV domains results in primary photochemical changes that lead to the uncaging of the kinase domain and its activation by the unfolding of the Jα-helix
Which one of the following combination of above statements is correct?
#Question id: 10465
#Unit 6. System Physiology – Plant
This feature is an adaptive, as the redistribution of
chloroplasts within the cells modulates light absorption and prevents
photodamage, diagram shows of chloroplast distribution patterns in Arabidopsis
palisade cells in response to different light intensities;
m) A-low light, B-high light, C-darkness
n) A-high light, B-darkness, C-low light
Based on the above light intensities, each shows
different chloroplasts position such as,
i) chloroplasts avoid sunlight by migrating to the
side walls of palisade cells
ii) chloroplasts move to the bottom of the cell,
although the physiological function of this position is unclear
iii) chloroplasts optimize light absorption by
accumulating at the upper and lower sides of palisade cells
Which of the following correct combinations shows light intensities and chloroplast movements?
#Question id: 10466
#Unit 6. System Physiology – Plant
In Arabidopsis, phot1 mutants have a normal avoidance response and a poor accumulation response, phot2 mutants lack the avoidance response but retain a fairly normal accumulation response, while phot1/phot2 double mutant lack both the avoidance and accumulation responses. These results indicate that,
#Question id: 10467
#Unit 6. System Physiology – Plant
The COP1-SPA complex acts as a positive regulator as well as acts as negative regulator by shown in statements;
a) Act as negative regulator−that targets transcription factors for degradation during phytochrome and cryptochrome responses
b) Acts as a positive regulator−that targets transcription factors for degradation during phytochrome and cryptochrome responses
c) Acts as a negative regulator− during UV-B signaling by interacting with the C-terminal region of UVR8 in the nucleus UVR8- COP1-SPA complex then activates the major transcription factor HY5, which controls the expression of many of the genes induced by UV-B
d) Acts as a positive regulator during UV-B signaling by interacting with the C-terminal region of UVR8 in the nucleus UVR8- COP1-SPA complex then activates the major transcription factor HY5, which controls the expression of many of the genes induced by UV-B
Whichof the following combination from avbove statements of UVR8 is true?