#Question id: 11810
#Unit 6. System Physiology – Plant
An experiment was done to see the effect of auxin: cytokinin ratios on morphogenesis can also be seen in crown gall tumors by mutation of the T-DNA of the Agrobacterium Ti plasmid,
I) Mutating the ipt gene (the tmr locus) of the Ti plasmid blocks zeatin biosynthesis in the infected cells
II) mutating either of the genes for auxin biosynthesis (tms locus)
Given some results about these above mutations ,
a) equal auxin to cytokinin ratio form undifferentiated callus tissue
b) high auxin:cytokinin ratio in the tumor cells causes the proliferation of roots instead of undifferentiated callus tissue
c) lowers the auxin:cytokinin ratio and stimulates the proliferation of shoots
What would be the result of these two mutation ?
#Question id: 11811
#Unit 6. System Physiology – Plant
The expression of IPT gene in the stress is driven by___
#Question id: 11812
#Unit 6. System Physiology – Plant
The nitrogens at the 3, 7, and 9 positions of the adenine ring of cytokinins can be conjugated to glucose residues, Alanine can also be conjugated to the nitrogen at the 9 positon, forming
#Question id: 11813
#Unit 6. System Physiology – Plant
Cytokinin-overproducing plants exhibit several
characteristics that point to roles played by cytokinin in plant physiology and
development:
a) shoot apical meristems of cytokinin-overproducing plants
produce more leaves.
b) Adventitious shoots may form from unwounded leaf veins
and petioles.
c) Leaf senescence is retarded.
d) more extreme cytokinin-overproducing plants are stunted,
with greatly shortened internodes.
e) Apical dominance is greatly increased
Which of the following statements of above given overproducing cytokinin plants is correct?
#Question id: 11814
#Unit 6. System Physiology – Plant
Simplified biosynthetic pathway for cytokinin biosynthesis
followed given such steps;
a) isopentenyl transferase (IPT), is the addition of the
isopentenyl side chain from DMAPP (dimethylallyl diphosphate) to an adenosine
moiety (AMP)
b) iPRTP or iPRDP is converted to ZTP or ZDP respectively by
cytochrome P450 monooxygenase and
eventually is converted to zeatin
c) The ribotide and riboside forms of trans-zeatin can be
interconverted, and free transzeatin can be formed from the ribotide by the
LONELY GUY (LOG) family of cytokinin
Which of the following steps is true of the cytokinin biosynthesis?
#Question id: 11815
#Unit 6. System Physiology – Plant
Some given statements about
the cytokinin signalling pathway;
a) Cytokinin receptor
CRE1 probably functions as a monomer
b) Two other hybrid sensor kinases (AHK2 and AHK3) may also
act as cytokinin receptors in Arabidopsis
c) Activated receptor activates their histidine kinase
activity, The phosphate is transferred to an aspartate residue (D) on the fused
receiver domains
d) The phosphate is then transferred to a conserved
histidine present in an AHP protein that transfer the phosphate to an aspartate
residue located within the receiver
domain of type-B ARRs only
e) The phosphorylation of the type-B ARR activates the
output domain to induce transcription of genes encoding type-A ARRs.
f) The phosphorylated type-A ARRs feed back to negatively
regulate cytokinin signaling, thus dampening cytokinin responses
Which of the following are the correct prediction about cytokinin signalling?