Calcium Signaling and Indicators Quiz

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Questions and Answers

What is the name of the calcium indicator that uses a single fluorescent protein with different colors for distinguishing calcium signals in different compartments?

  • GECO (correct)
  • CaM
  • GCaMP
  • GFP

The calcium response from a caterpillar biting a leaf is localized to the bite site.

False (B)

What are two ways calcium signals can vary based on the stimulus?

Calcium signals can vary in their lag phase (time delay before the signal starts), rise time (how long it takes to reach its peak), total transient length, shape, and location within the cell.

The GCaMP indicator relies on the binding of calcium to ______ for generating light.

<p>calmodulin</p> Signup and view all the answers

Match the following calcium indicator types with their primary components:

<p>GCaMP = GFP, calmodulin GECO = Single fluorescent protein GFP = Green fluorescent protein</p> Signup and view all the answers

Calcium sensor proteins can have enzymatic activity.

<p>True (A)</p> Signup and view all the answers

Which of the following is NOT a characteristic of calmodulin (CaM)?

<p>It is primarily involved in regulating gene expression. (C)</p> Signup and view all the answers

Calcium sensor proteins undergo a ______ change upon binding calcium, exposing hydrophobic regions that interact with target proteins.

<p>conformational</p> Signup and view all the answers

What are the two main types of calcium sensor proteins?

<p>Sensor relays and sensor responders</p> Signup and view all the answers

Match the following calcium sensor proteins with their characteristics:

<p>Calmodulin (CaM) = Has 4 EF hands and acts as a sensor relay. Calcium-dependent protein kinases (CDPKs) = Has both calcium binding and kinase activity. Calmodulin-like proteins (CMLs) = Can have different numbers of EF hands and act as sensor relays. Sensor responders = Possess both calcium binding and enzymatic activity.</p> Signup and view all the answers

What is the primary function of calcium-dependent protein kinases (CDPKs)?

<p>To phosphorylate target proteins. (A)</p> Signup and view all the answers

Calmodulin-like proteins (CMLs) are only found in plants.

<p>False (B)</p> Signup and view all the answers

What is the significance of the variable sequence in CDPKs?

<p>The variable sequence in CDPKs is responsible for their membrane association, allowing them to localize to different cellular compartments.</p> Signup and view all the answers

Which of the following molecules is the intermediate in the IAM pathway?

<p>indole-3-acetamide (B)</p> Signup and view all the answers

The IPA pathway is identical to the canonical pathway for auxin synthesis.

<p>False (B)</p> Signup and view all the answers

What is the primary function of auxin conjugation?

<p>Storage or degradation of auxins</p> Signup and view all the answers

The ______ transport of auxins is directional and occurs from the shoot apex to the root apex.

<p>polar</p> Signup and view all the answers

Match the following auxin synthesis pathways with their corresponding intermediates:

<p>IPA = indole-3-pyruvic acid IAN = indole-3-acetonitrile IAM = indole-3-acetamide Tryptophan-independent = indole-3-glycerol phosphate</p> Signup and view all the answers

Which of the following is NOT a common method of auxin storage?

<p>Conjugation with lipids (A)</p> Signup and view all the answers

Apolar auxin transport is a passive process that occurs through the xylem.

<p>False (B)</p> Signup and view all the answers

What is the significance of the tryptophan-independent auxin synthesis pathway?

<p>It demonstrates that auxin synthesis can occur even in the absence of tryptophan.</p> Signup and view all the answers

Which of these is NOT a factor that regulates gibberellin metabolism?

<p>DNA replication (C)</p> Signup and view all the answers

The hydroxylation pathway of gibberellin synthesis uses different enzymes than the non-hydroxylation pathway.

<p>False (B)</p> Signup and view all the answers

What is the effect of high concentrations of active gibberellins on the expression of the GA20ox and GA3ox genes?

<p>High concentrations of active gibberellins inhibit the expression of GA20ox and GA3ox genes.</p> Signup and view all the answers

The ______ mutant is very tall because there is no inactivation of gibberellin.

<p>slender</p> Signup and view all the answers

Match the gibberellin-related enzymes with their corresponding functions:

<p>GA20 oxidase = Oxidative reactions leading to 19C GA GA3 oxidase = Hydroxylation at C3 GA2 oxidase = Gibberellin inactivation</p> Signup and view all the answers

What is the final product of the non-hydroxylation pathway of gibberellin synthesis?

<p>GA with 19C (B)</p> Signup and view all the answers

Gibberellins are only produced in the shoot apex.

<p>False (B)</p> Signup and view all the answers

Describe the role of the GUS reporter gene in studying gibberellin synthesis.

<p>The GUS reporter gene produces a blue color when added with the right substrate, allowing researchers to visualize the location and activity of gibberellin biosynthesis pathways. For instance, GUS can be used to determine the locations where gibberellins are produced within a plant.</p> Signup and view all the answers

What is the primary difference between cis and trans forms of cytokinins?

<p>The orientation of the double bond in their structure (C)</p> Signup and view all the answers

Cytokinins can be inactivated by the addition of sugar or phosphate groups.

<p>True (A)</p> Signup and view all the answers

What is the name of the enzyme that catalyzes the transfer of an isopentenylic group to adenine, leading to the formation of transzeatin?

<p>Isopentenyl transferase (IPT)</p> Signup and view all the answers

The uncontrolled growth of lateral buds due to cytokinin activity can lead to the development of a phenomenon known as ______, characterized by the formation of bundles of branches along the stem.

<p>fasciation</p> Signup and view all the answers

Match the following processes with their effect on cytokinin activity:

<p>Oxidative cleavage = Irreversible inactivation N-glucosylation = Irreversible inactivation O-glucosylation = Reversible inactivation</p> Signup and view all the answers

Which of the following is NOT a common site of cytokinin production in plants?

<p>Leaf blades (C)</p> Signup and view all the answers

Pathogenic bacteria and fungi can produce cytokinins that affect plant growth.

<p>True (A)</p> Signup and view all the answers

Name a bacterial species that produces cytokinins and causes the formation of crown galls on plants.

<p>Agrobacterium tumefaciens</p> Signup and view all the answers

Ethylene, a gaseous plant hormone, is synthesized from the precursor molecule ______ through a series of enzymatic steps.

<p>methionine</p> Signup and view all the answers

Which of the following is NOT a characteristic of the triple response exhibited by plants treated with ethylene?

<p>Promotion of upright growth (A)</p> Signup and view all the answers

What is the name of the chemical used to mimic the effects of ethylene in plants?

<p>Ethephon</p> Signup and view all the answers

Ethylene is only produced by ripening fruit, not by other parts of the plant.

<p>False (B)</p> Signup and view all the answers

Match the following enzymes involved in ethylene biosynthesis with their corresponding functions:

<p>AdoMet synthase = Converts methionine to S-Adenosylmethionine ACC synthase = Transforms S-Adenosylmethionine to ACC ACC oxidase = Oxidizes ACC to ethylene</p> Signup and view all the answers

Which of these is the direct precursor to ethylene biosynthesis?

<p>ACC (B)</p> Signup and view all the answers

Briefly describe how ethylene was discovered as a plant hormone.

<p>Scientists observed that etiolated seedlings grew abnormally short and thick in enclosed spaces. When ventilation was introduced, the plants recovered. Analysis of the air revealed the presence of ethylene, which was later confirmed to be produced by ripening apples, indicating its biological activity in plants.</p> Signup and view all the answers

Ethylene is very effective in promoting plant growth at high concentrations.

<p>False (B)</p> Signup and view all the answers

Flashcards

GCaMP

A genetically encoded calcium indicator that fluoresces in response to calcium binding with calmodulin.

Calcium Response

The increase in calcium ions concentration signaling a cellular response.

Calcium Transient

A temporary increase in calcium ion concentration in response to stimuli.

GECO

Genetically Encoded Calcium Indicator that uses different colors to indicate calcium levels in different compartments.

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Calcium Signature

The unique pattern of calcium signaling specific to different stimuli characterized by lag phase, rise time, and shape.

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Stimulus Specificity

The ability of calcium signals to vary based on the type of stimulus received.

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Calcium Sources

Origins of calcium influx in cells, such as from the ER, vacuole, or mitochondria.

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Calcium Propagation

The means by which a calcium signal spreads through a plant or cell, possibly via floem or ROS.

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Binding Site

A region on a protein with high affinity for calcium.

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Conformational Change

A structural alteration of a protein after binding calcium.

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Calcium Sensor Proteins

Proteins that detect calcium and mediate cellular responses.

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Calmodulin (CaM)

A small protein with 4 EF hands that binds calcium and regulates targets.

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Calmodulin-like Proteins (CMLs)

Proteins similar to CaM with variations in EF hands and identity.

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Sensor Responders

Proteins that combine calcium binding with enzymatic activity.

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Calcium-dependent Protein Kinases (CDPKs)

Plant-specific kinases activated by calcium that phosphorylate target proteins.

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IPA

Indole-3-pyruvic acid, an auxin precursor in plants.

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IAN

Indole-3-acetonitrile, lacks the final oxidation step.

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IAM

Indole-3-acetamide, an intermediate in Agrobacterium infections.

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Tryptophan-independent pathway

A plant pathway producing IAA without producing Trp.

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Auxin metabolism

Involves conjugation for storage or degradation.

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Apolar transport

Hormone movement through phloem, passive and quick.

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Polar transport

Directional auxin transport from shoot apex to root apex.

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Conjugation in auxins

Reversible for storage, irreversible if oxidized.

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Ethylene

A plant hormone that influences growth, particularly in response to stress.

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Triple response

The three effects of ethylene on plant growth: reduced elongation, increased lateral growth, and horizontal growth.

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AdoMet synthase

An enzyme that converts methionine into S-Adenosylmethionine, a precursor in ethylene biosynthesis.

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ACC synthase

An enzyme that converts S-Adenosylmethionine into 1-Aminocyclopropane-1-carboxylic acid (ACC).

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ACC oxidase

An enzyme that converts ACC into ethylene in the presence of oxygen.

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Ethephon

A chemical compound that releases ethylene and is used in agriculture to promote ripening.

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Ethylene's concentration effect

Ethylene is active even at very low concentrations in plants.

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Phase of growth in seedlings

Ethylene causes seedlings to grow short, thick, and horizontally under stress.

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Gibberellins (GAs)

Hormones that promote plant growth and development, particularly in elongation.

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Hydroxylation Pathway

A metabolic route producing active GAs through hydroxylation of C13.

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Non-Hydroxylation Pathway

Alternative metabolic route producing GA with 19C that has biological activity.

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GA20 oxidase

An enzyme that catalyzes reactions producing active gibberellins.

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Feedback Regulation

Process where high GA levels repress their own synthesis.

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GA2 oxidase

An enzyme that inactivates gibberellins, leading to decreased growth.

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Photoperiod Regulation

Control of GA production based on day length, influencing plant growth.

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Transgenic Reporter GUS

A gene used as a marker that produces a blue color when activated, indicating GA presence.

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CIS and TRANS isomers

Two configurations of molecules with a double bond, commonly found in cytokinins.

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Cytokinins

Plant hormones that promote cell division and growth.

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Isopentenylic group

A molecular group derived from adenine, essential for biosynthesis of cytokinins.

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Transzeatine

A type of cytokinin first produced from adenine in plants.

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Cytokinin inactivation

The process of reducing or eliminating the effect of cytokinins in plants.

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Fasciation

Abnormal growth in plants causing lateral branches to proliferate uncontrollably.

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IPT enzyme

Isopentenyl transferase that facilitates the biosynthesis of cytokinins.

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N-glucosylation

Modification of the adenine ring that leads to irreversible inactivation of cytokinins.

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Study Notes

Calcium-Mediated Signal Transduction in Plants

  • Calcium is a crucial intracellular messenger, playing a key role in plant signal transduction in response to both biotic and abiotic stimuli.
  • Signals can be physical (e.g., temperature, light, touch) or chemical (e.g., pathogens, symbionts).
  • Calcium signals trigger physiological responses like defense mechanisms or adaptation strategies.
  • Changes in cytosolic calcium concentration, usually an increase, are the primary triggers for various physiological responses.

Calcium Homeostasis and Signal Transduction

  • Resting cytosolic calcium concentration is low (10−7 M) but increases dramatically in response to stimuli (0.5-5µM).
  • Apoplastic calcium concentration is high (10−3 M).
  • Organelles like the vacuole store significant calcium (e.g., 80mM).
  • Membrane proteins, including channels and pumps, maintain calcium homeostasis, transporting calcium into and out of the cytosol.

Calcium Transporters and Channels

  • Calcium permeable channels, which don't use energy, allow calcium movement along its concentration gradient.
  • Voltage-gated, mechanosensitive, and ligand-gated channels are different types of calcium channels.
  • Active calcium transporters, powered by ATP, regulate calcium levels against the gradient, in the plasma membrane, ER, vacuole, and nuclear envelope.
  • Calcium pumps are secondary transporters that use the energy from other ions to move calcium against the gradient

Methods to Measure Calcium

  • Fluorescent dyes (e.g., Calcium Green, Fluo-3, Indo-1, Fura-2) change fluorescence intensity in response to calcium.
  • Protein-based calcium indicators (e.g., Aequorin, Cameleon) convert calcium binding into light emission.
  • GECIs (genetically encoded calcium indicators), a newer technology, allow direct observation of calcium in living cells.

Protein Targeting

  • Proteins are specifically targeted to different cellular compartments (e.g., cytosol, vacuoles, mitochondria) to execute specialized functions.
  • Targeting sequences (e.g., signal peptides, transit peptides) direct proteins to designated destinations within the cell.

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