This member of the AKAP family, designated mAKAP, anchors both PDE and the regulatory subunit  of PKA to the nuclear membrane, maintaining them in a negative feedback loop that provides close local control of the ATP level and PKA activity.

B- The basal level of PDE activity in the presence of hormone (resting state) keeps cAMP levels below those necessary for PKA activation. 

C- Activation of β-adrenergic receptors causes an increase in cAMP to a level in excess of that which can be degraded by PDE. 

D- The resulting binding of cAMP to the R subunits of PKA releases the active catalytic (C) subunits into the cytosol. Some C subunits enter the nucleus, where they phosphorylate and thus activate certain transcription factors . Other C subunits phosphorylate PDE, stimulating its catalytic activity.

E-  Active PDE hydrolyzes cAMP, thereby driving cAMP levels back to basal levels and causing re-formation of the inactive PKA C-R complex. Subsequent de-phosphorylation of PDE returns the complex to the resting state.

TLS Online TPP Program

#Question id: 10418

#Unit 6. System Physiology – Plant

What is the reason behind that the PAS-related domain (PRD) is only present in the Plant phytochrome, but absent in cyanobacterial Cph1 and Bacterial BphP?

TLS Online TPP Program

#Question id: 10419

#Unit 6. System Physiology – Plant

The conversion of Pr to Pfr by red light, both phyA and phyB move from the cytosol into the nucleus in a light-dependent fashion.

a) Both have nuclear localization signal (NLS) sequences

b) PRD domain of phyB can potentially serve as an NLS, but it is apparently masked in the Pr form

c) phyA dependent on other proteins, such as FAR-RED ELONGATED HYPOCOTYL1 (FHY1) facilitating phyA’s transport it into the nucleus

d) Both phyA and phyB have PRD domain serve as an NLS and responsible for import into the nucleus only in pfr form may expose the functional NLS of the PRD domain

Which of the following factors is involved for transporting phyA and B into the nucleus?

TLS Online TPP Program

#Question id: 10420

#Unit 6. System Physiology – Plant

 A toggle model has been proposed for phytochrome interconversion, according to this model which option is correct?

TLS Online TPP Program

#Question id: 10421

#Unit 6. System Physiology – Plant

The red light-induced rotation of the D ring of the chromophore causes the hairpin to become helical, which of the following β-hairpin changes conformation after rotation?

TLS Online TPP Program

#Question id: 10422

#Unit 6. System Physiology – Plant

Arabidopsis contains five genes encoding phytochromes, PHYA–PHYE, four of the five phytochromes appear mostly light-stable in the plant and function primarily in the regulation of LFRs and of shade avoidance involving changes in the R:FR ratio.

TLS Online TPP Program

#Question id: 10423

#Unit 6. System Physiology – Plant

Which of the following responses include processes such as the promotion of lettuce seed germination, inhibition of hypocotyl elongation, and regulation of leaf movements?