BIOL3002 EXAM STUDY SET WITH
VERIFIED SOLUTION
What is a non-cell autonomous response? - ANSWER External signals or cues from
neighboring cells or the environment that influence a cell's behavior.
Give examples of non-cell autonomous responses. - ANSWER Immune cells responding
to signals from infected cells, stem cells differentiating in response to signals from
nearby cells or tissues.
What are the common mechanistic features in hormone-regulated pathways? - ANSWER
Hormone secretion, activation, target cell interaction, receptor binding, signal
transduction, genomic and non-genomic response.
Where are receptors located in plant cells? - ANSWER Membrane-bound (e.g.
cytokinins) or soluble in the cytoplasm (e.g. ABA interacts with PYR1).
How are hormone signaling responses terminated? - ANSWER Pathways initiated when
a dynamic threshold is reached, degradation, inactivation/conjugation, sequestration,
efflux.
What precursors are used to make ABA? - ANSWER ABA is synthesized from xanthoxin,
derived from zeaxanthin, a carotenoid pigment found in chloroplasts.
How is ABA inactivated? - ANSWER Monosaccharide conjugation or oxidation.
What phenotypes would you expect in a mutant unable to synthesize ABA? - ANSWER
Reduced stress tolerance, impaired seed dormancy, stomatal regulation defects,
reduced response to wounding, altered growth and development, increased
susceptibility to pathogens, altered nutrient uptake, altered fruit ripening.
What responses would you expect in a drought-stressed plant? - ANSWER Consider
ABA signaling as a whole.
What is the role of ABA in stomatal closure? - ANSWER ABA drives efflux of ions,
decreasing turgor pressure in guard cells.
What are the effects of ABA in the long term? - ANSWER Inhibition of shoot growth,
promotion of root growth, increasing root:shoot ratio.
What is seed dormancy? - ANSWER Unable to germinate in a specified period of time
under suitable conditions.
How do ABA and GA control seed dormancy and germination? - ANSWER ABA is
catabolized and GA is synthesized for germination. ABA upregulates a protein kinase to
,inhibit germination expression.
What is the evolutionary advantage of seed dormancy? - ANSWER Plays a role in plant
evolution and adaptation to climactic changes. May determine survival during climate
change.
How does stomatal opening occur fast in response to rehydration? - ANSWER ABA is
converted to phaseic acid.
What are the effects of cytokinins on cell division? - ANSWER Stimulate lateral bud
growth and formation of new shoots and branches.
What are the effects of cytokinins independent of cell division? - ANSWER Delay leaf
senescence, regulate nutrient allocation, promote root nodule formation, and regulate
auxin action.
How do CK and auxin interact in tissue experiments using tobacco leaf discs? -
ANSWER Promote both root and shoot development.
What is the effect of high concentrations of cytokinins? - ANSWER Promote shoot
development
What is the effect of high concentrations of auxin? - ANSWER Promote root development
What determines whether tissue develops roots, shoots, or both? - ANSWER Balance
between cytokinins and auxin
Why does the plant have inactive cytokinins? - ANSWER To allow for transport and
activation
How are inactive cytokinins activated? - ANSWER Through dephosphorylation and
de-ribosylation
How can cytokinins be inactivated? - ANSWER Through conjugation with glycosylation
or acetylation, or degradation
What phenotypes occur in plants with elevated levels of cytokinins? - ANSWER Reduced
apical dominance, reduced root growth, delayed leaf senescence
What phenotypes occur in plants with reduced levels of cytokinins? - ANSWER
Accelerated senescence, reduced shoot growth, enhanced root growth
How are different types of cytokinins perceived differently in roots and shoots? -
ANSWER Through different receptors with different sensitivities
How can one demonstrate the paracrine function of cytokinins? - ANSWER By grafting
wild type plants to ipt mutant plants
What is the paracrine function of cytokinins? - ANSWER Short-distance/localized
signaling
, How can one demonstrate the long distance function of cytokinins? - ANSWER By
grafting wild type plants to ipt mutant plants and observing rescue of phenotype
throughout the entire plant
What is the long distance function of cytokinins? - ANSWER Signaling over long
distances
What is the role of the LONELY GUY enzyme? - ANSWER To activate cytokinins through
dephosphorylation and de-ribosylation
What are the two forms of cytokinins in plants? - ANSWER Active and inactive forms
What is the purpose of reversible conjugation with glycosylation or acetylation? -
ANSWER To inactivate cytokinins
What is the purpose of irreversible degradation? - ANSWER To inactivate cytokinins
What is the sensitivity of shoots to cytokinin? - ANSWER TZ cytokinin
What is the sensitivity of roots to cytokinin? - ANSWER IP cytokinin
What is the effect of IPT overexpression? - ANSWER Reduced apical dominance,
reduced root growth, delayed leaf senescence
What is the effect of IPT underexpression? - ANSWER Accelerated senescence, reduced
shoot growth, enhanced root growth
How to improve crops via cytokinin modification? - ANSWER Grafting of transgenic plant
with inducible promoter for IPT showed that lateral bud formation is promoted.
What is meant by partially redundant in Arabidopsis cytokinin receptors? - ANSWER
AHK2, AHK3, and AHK4 produce similar outcomes but have unique properties.
Explain how auxin and cytokinin work together to regulate root meristem function. -
ANSWER High auxin inhibits cytokinin biosynthesis, while high cytokinin inhibits auxin
transport and response.
What is the purpose of aquaporins? - ANSWER Aquaporins support solute transport and
separation in plants.
What is the naming convention for aquaporins? - ANSWER Species, AQP sub-family,
isoform.
What are the characteristics of the monomeric pore in aquaporin? - ANSWER The Ar/R
filter acts as a size exclusion barrier with hydrophilic and hydrophobic selectivity, and
NPA residues allow formation of hydrogen bonds.
What is the role of Loop D in aquaporins? - ANSWER Undergoes conformational
VERIFIED SOLUTION
What is a non-cell autonomous response? - ANSWER External signals or cues from
neighboring cells or the environment that influence a cell's behavior.
Give examples of non-cell autonomous responses. - ANSWER Immune cells responding
to signals from infected cells, stem cells differentiating in response to signals from
nearby cells or tissues.
What are the common mechanistic features in hormone-regulated pathways? - ANSWER
Hormone secretion, activation, target cell interaction, receptor binding, signal
transduction, genomic and non-genomic response.
Where are receptors located in plant cells? - ANSWER Membrane-bound (e.g.
cytokinins) or soluble in the cytoplasm (e.g. ABA interacts with PYR1).
How are hormone signaling responses terminated? - ANSWER Pathways initiated when
a dynamic threshold is reached, degradation, inactivation/conjugation, sequestration,
efflux.
What precursors are used to make ABA? - ANSWER ABA is synthesized from xanthoxin,
derived from zeaxanthin, a carotenoid pigment found in chloroplasts.
How is ABA inactivated? - ANSWER Monosaccharide conjugation or oxidation.
What phenotypes would you expect in a mutant unable to synthesize ABA? - ANSWER
Reduced stress tolerance, impaired seed dormancy, stomatal regulation defects,
reduced response to wounding, altered growth and development, increased
susceptibility to pathogens, altered nutrient uptake, altered fruit ripening.
What responses would you expect in a drought-stressed plant? - ANSWER Consider
ABA signaling as a whole.
What is the role of ABA in stomatal closure? - ANSWER ABA drives efflux of ions,
decreasing turgor pressure in guard cells.
What are the effects of ABA in the long term? - ANSWER Inhibition of shoot growth,
promotion of root growth, increasing root:shoot ratio.
What is seed dormancy? - ANSWER Unable to germinate in a specified period of time
under suitable conditions.
How do ABA and GA control seed dormancy and germination? - ANSWER ABA is
catabolized and GA is synthesized for germination. ABA upregulates a protein kinase to
,inhibit germination expression.
What is the evolutionary advantage of seed dormancy? - ANSWER Plays a role in plant
evolution and adaptation to climactic changes. May determine survival during climate
change.
How does stomatal opening occur fast in response to rehydration? - ANSWER ABA is
converted to phaseic acid.
What are the effects of cytokinins on cell division? - ANSWER Stimulate lateral bud
growth and formation of new shoots and branches.
What are the effects of cytokinins independent of cell division? - ANSWER Delay leaf
senescence, regulate nutrient allocation, promote root nodule formation, and regulate
auxin action.
How do CK and auxin interact in tissue experiments using tobacco leaf discs? -
ANSWER Promote both root and shoot development.
What is the effect of high concentrations of cytokinins? - ANSWER Promote shoot
development
What is the effect of high concentrations of auxin? - ANSWER Promote root development
What determines whether tissue develops roots, shoots, or both? - ANSWER Balance
between cytokinins and auxin
Why does the plant have inactive cytokinins? - ANSWER To allow for transport and
activation
How are inactive cytokinins activated? - ANSWER Through dephosphorylation and
de-ribosylation
How can cytokinins be inactivated? - ANSWER Through conjugation with glycosylation
or acetylation, or degradation
What phenotypes occur in plants with elevated levels of cytokinins? - ANSWER Reduced
apical dominance, reduced root growth, delayed leaf senescence
What phenotypes occur in plants with reduced levels of cytokinins? - ANSWER
Accelerated senescence, reduced shoot growth, enhanced root growth
How are different types of cytokinins perceived differently in roots and shoots? -
ANSWER Through different receptors with different sensitivities
How can one demonstrate the paracrine function of cytokinins? - ANSWER By grafting
wild type plants to ipt mutant plants
What is the paracrine function of cytokinins? - ANSWER Short-distance/localized
signaling
, How can one demonstrate the long distance function of cytokinins? - ANSWER By
grafting wild type plants to ipt mutant plants and observing rescue of phenotype
throughout the entire plant
What is the long distance function of cytokinins? - ANSWER Signaling over long
distances
What is the role of the LONELY GUY enzyme? - ANSWER To activate cytokinins through
dephosphorylation and de-ribosylation
What are the two forms of cytokinins in plants? - ANSWER Active and inactive forms
What is the purpose of reversible conjugation with glycosylation or acetylation? -
ANSWER To inactivate cytokinins
What is the purpose of irreversible degradation? - ANSWER To inactivate cytokinins
What is the sensitivity of shoots to cytokinin? - ANSWER TZ cytokinin
What is the sensitivity of roots to cytokinin? - ANSWER IP cytokinin
What is the effect of IPT overexpression? - ANSWER Reduced apical dominance,
reduced root growth, delayed leaf senescence
What is the effect of IPT underexpression? - ANSWER Accelerated senescence, reduced
shoot growth, enhanced root growth
How to improve crops via cytokinin modification? - ANSWER Grafting of transgenic plant
with inducible promoter for IPT showed that lateral bud formation is promoted.
What is meant by partially redundant in Arabidopsis cytokinin receptors? - ANSWER
AHK2, AHK3, and AHK4 produce similar outcomes but have unique properties.
Explain how auxin and cytokinin work together to regulate root meristem function. -
ANSWER High auxin inhibits cytokinin biosynthesis, while high cytokinin inhibits auxin
transport and response.
What is the purpose of aquaporins? - ANSWER Aquaporins support solute transport and
separation in plants.
What is the naming convention for aquaporins? - ANSWER Species, AQP sub-family,
isoform.
What are the characteristics of the monomeric pore in aquaporin? - ANSWER The Ar/R
filter acts as a size exclusion barrier with hydrophilic and hydrophobic selectivity, and
NPA residues allow formation of hydrogen bonds.
What is the role of Loop D in aquaporins? - ANSWER Undergoes conformational
