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#Question id: 12400

#Unit 6. System Physiology – Plant

Given  some  statements  about auxin  signal  transduction  pathway;

a) ARFs bind the AuxRE stably, must form dimers promote transcription by binding to two AuxREs arranged in a palindrome

b) inactive heterodimers may act to inhibit ARF–AuxRE binding, thereby blocking either gene activation or repression

c) Protein encodes the AUX/IAA gene family can inhibit the transcription of early auxin response genes by forming inactive heterodimers with ARFs

d) Auxin induces the transcription of the early response genes by promoting the proteolytic degradation of the inhibitory AUX/IAA proteins so that active ARF dimers can form

e) AUX/IAA turnover to involve ubiquitination by a ubiquitin ligase and proteolysis by the massive 26S proteasome complex

f) A negative feedback loop is introduced into the pathway by virtue of the fact that one of the gene families turned on by auxin is AUX/IAA, which inhibits the response.

Find out the correct sequence from the following above statements;

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#Question id: 12395

#Unit 6. System Physiology – Plant

In theory, auxin could increase the rate of proton extrusion by two possible mechanisms:

I) H+-ATPase activation

II) H+-ATPase synthesis

a) Auxin involves in the activation of ATP-driven proton-pump (H+-ATPase) indirectly

b) ABPs appear to be able to activate the plasma membrane H+-ATPase in the presence of auxin

c) Activity of the H+- ATPase is repressed by the C-terminal domain of the enzyme, which can block the catalytic site  in absence of auxin

d) The protein is synthesized on the rough endoplasmic reticulum and targeted via the secretory pathway to the plasma membrane

Find out the correct explanation of given mechanisms.

TLS Online TPP Program

#Question id: 12201

#Unit 6. System Physiology – Plant

ARF dependent signalling are regulated by auxin concenteration, given some condition followed;

I) In the absence of auxin

 II) In the presence of auxin

Find the statements that are correctly matched with given certain condition,

a)  AUX/IAA repressor proteins containing interaction domains similar to those found in the ARFs form heterodimers with the ARFs and thus repress transcriptional activation

b)  AUX/IAA repressors are recruited to the TIR1/AFB receptor complex and are tagged with ubiquitin for degradation by the 26S proteasome

c) ARFs form homodimers via conserved interaction domains and recruit chromatin remodelling

Which of the following combination is correct?

TLS Online TPP Program

#Question id: 12200

#Unit 6. System Physiology – Plant

Given some observation of the auxin signalling pathway, which one of the following are the incorrect prediction about signalling?

TLS Online TPP Program

#Question id: 12199

#Unit 6. System Physiology – Plant

Some given statements about Auxin signalling pathways are listed;

a) The auxin receptor is composed of two proteins: the SCF complex component TIR1 and the repressor protein AUX/IAA

b) The binding of auxin to its receptor complex initiates ubiquitin-dependent degradation of the AUX/ IAA repressor protein by the 26S proteasome 

c) TIR1 recruits AUX/ IAA proteins to the SCFTIR1  complex in an auxin-independent manner

d) AUX/IAA proteins are ubiquitinated by the E3 ligase activity of the SCFTIR1 complex, which marks the protein for destruction by the 26S proteasome

Which of the following is correct explanation of Auxin signalling pathways?

TLS Online TPP Program

#Question id: 12198

#Unit 6. System Physiology – Plant

In theory, auxin could increase the rate of proton extrusion by some possible mechanisms such as:

a) Activation of pre-existing plasma membrane H+- ATPases

b) Synthesis of new H+-ATPases on the plasma membrane

c) Auxin-Induced Proton Extrusion May Involve Both Activation and Synthesis