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Plant Phys > Plant Hormones and Signal Transduction - 12 > Flashcards

Plant Hormones and Signal Transduction - 12 Flashcards

1
Q

Define signal

A

environmental input that initiates one or more plant responses

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2
Q

Define receptor

A

the physical component that biochemically responds to a signal

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3
Q

What do receptors consist of

A

proteins or pigments associated with proteins (if light receptors)

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4
Q

What are the 4 chain of events that the signal transduction pathways typically involve

A

signal -> receptor -> signal transduction -> response

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5
Q

signal transductions can cause both rapid and slow responses, explain the difference in responses

A

rapid responses involve electrochemical responses

longer/slower involve changes in gene expression

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6
Q

plant responses to environmental signals can differ ____ and/or ___

A

time or spatially

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7
Q

Define cell autonomous response vs. non-cell autonomous response (is how plant responses differ spatially) and examples

A

cell autonomous = response to environmental signal where both the signal reception and response occur in the same cell (ex. guard cell)
non-cell = signal reception occurs in one cell and the response occurs in a different cell (ex. stomata)

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8
Q

where are the 4 places receptors can be located

A

plasma membrane, cytosol, endomembrane system, or nucleus
or found in more than 1 cellular location!

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9
Q

Define kinase

A

an enzyme that catalyzes the transfer of a phosphate group from ATP to a specified molecule (most common modification)

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10
Q

Define secondary messenger and what is the most common one

A

Ca2+
released in response to the primary messengers which are transported to the site of action to evoke the main physiological response

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11
Q

What are strategies for kinases to amplify signal transduction pathways (2)

A

Kinases = elevate weak initial signaling events above the threshold of detection or to propagate throughout the cytoplasm

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12
Q

Explain the processes of activation and termination of the secondary messenger Ca2+

A

signal induced activation of Ca2+ permeable ion channels in cytoplasm, activated sensor proteins interact and link signals to changes in activity -> can activate calmodulin by binding or phosphorylate target proteins, pumps and exchangers remove Ca2+ from cytoplasm and terminate signal

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13
Q

What is the secondary messenger Ca2+ mostly involved in

A

plant defenses and symbiotic interactions

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14
Q

what other factor can regulate Ca2+ fluxes

A

membrane lipids

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15
Q

Aside from Ca2+, what is another important secondary messenger

A

protons

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16
Q

Define hormones as chemical messengers

A

chemical messengers produced in one cell and modulate cell processes in another cell. they interact with specific proteins that function as receptors linked to cell signal transduction pathways

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17
Q

Explain the pathway of hormones

A

signal perception increases hormone biosynthesis -> hormone transported to site of action -> perception of hormone occurs by the receptor -> results in transcriptional or posttranscriptional events that induce a response -> suppress synthesis by negative feedback by catabolism or sequestration -> ready for next signal input

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18
Q

Plant development is regulated by what 9 major hormones

A
  1. auxin
  2. gibberellins
  3. cytokinins
  4. ethylene
  5. abscisic acid
  6. brassinosteroids
  7. salicylic acid
  8. jasmonates
  9. strigolactones
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19
Q

Auxin function

A

plant growth, growth regulator, embryo development in seeds, lateral branching, delaying leaf senescence

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20
Q

define polar auxin transport

A

directional auxin movement that functions in development and growth responses

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21
Q

Gibberellins function

A

transition to flowering, fruit development, growth promoting regulators

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22
Q

Cytokinins function

A

breaking bud dormancy, leaf senescence, formation of apical meristems, produced during mycorrhizal formation

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23
Q

What can cytokinins do in the presence of auxins

A

can stimulate plant tissue to produce parenchyma cells in undifferentiated masses called callus (cells that cover plant wound)

24
Q

Ethylene function

A

fruit ripening, leaf and flower senescence, epinasty

25
Q

Abscisic acid function (ABA)

A

promotes senescence, stomatal closure, seed maturation, responses to pathogens

26
Q

Function of brassionosteriods (BRs)

A

sex determination, elongation growth and photomorphogenesis

27
Q

Define salicylic acid and jasmonates

A

involved in plant defence responses to herbivory and pathogen infection

28
Q

Strigolactones function

A

promote symbiotic interactions with arbuscular mycorrhizal fungi, stimulate activity of cambium and secondary growth

29
Q

What is hormone concentration determined by

A

by the balance between the rate of increase of the hormone concentration (biosynthesis, uptake, activation, release) and rate of decrease of concentration (efflux, sequestration, degradation, inactivation)

30
Q

What are the 3 factors that makes regulation of hormone levels complicated

A
  1. may be augmented by secondary or intersecting biosynthesis mechanisms
  2. variants of a hormone can cause variability in the biological activity
  3. may be multiple mechanisms for removing active hormones from the system
31
Q

What hormone is toxic at high cellular concentrations and what can it be used for

A

auxins
used for herbicides

32
Q

how is auxin regulated (2)

A
  1. by being conjugation into conjugated forms and oxidatively degraded
  2. sequestered in ER
33
Q

What is the difference between natural and synthetic auxins

A

synthetic auxins can be herbicides because they are less subject to homeostasis control (sequestration and degradation) than natural auxins

34
Q

What are the 3 regulatory mechanisms for gibberlin biosynthesis and catabolism pathway

A
  1. gibberelin inactivation (GA 2-oxidases)
  2. methylation
  3. conjugation to sugars
35
Q

hormonal signaling involves transmission from _____ to ____

A

site of synthesis
site of action

36
Q

What are the 3 types of hormones in terms of transmission

A
  1. endocrine hormones
  2. paracrine hormones
  3. autocrine effectors
37
Q

Define endocrine hormones

A

hormones transported to sites of action distant from the site of synthesis

38
Q

Define paracrine hormones

A

hormones that can act on cells adjacent to the site of synthesis

39
Q

Define autocrine effectors

A

hormones that function in the same cells in which they are synthesized

40
Q

Explain why most plants have paracrine activities

A

because plants lack a fast-moving circulatory system so they have paracrine activities which transduces to nearby cells to cause an effect

41
Q

What is the most common electrical signaling in plants

A

action potential

42
Q

Define action potential

A

depolarization of the plasma membrane of a cell generated by voltage-dependent ion channels

43
Q

What kind of system do the cellular receptors for ethylene and cytokinins resemble

A

2-component regulatory systems

44
Q

define 2-component regulatory systems

A

consist of membrane bound histidine kinase sensor protein and soluble response regulator protein

45
Q

Explain signal movement through a 2-component regulatory system

A

the sensor proteins receive the input signal, undergo autophosphorylation, then pass signal on to response regulators by transferring phosphoryl group, then bring response

46
Q

Where are cytokinin and ethylene receptors localized

A

localized to endoplasmic reticulum membrane

47
Q

What do the largest class of plant receptor kinases consist of

A

receptor-like serine/threonine kinases (RLKs)

48
Q

function of RKLs

A

relay information to the cell interior by phosphorylation of serine or threonine residues of target proteins

49
Q

Define protein phosphatases

A

enzymes that remove phosphate groups from proteins that also have a role in signal transduction pathways

50
Q

Explain why plant hormone pathways employ negative regulators

A

negative regulators are inactivating repressors which allow for faster activation of downstream response genes. the pathways function by inactivating repressor proteins

51
Q

How do auxins, jasmonates, and gibberellins signal

A

by inactivating repressor proteins, directly targeting the stability of repressor proteins and thereby inducing a transcriptional response

52
Q

What are the 4 mechanisms in which plants terminate signals

A
  1. degradation
  2. inactivation of conjugation to ligands
  3. sequestration
  4. inactivation by dephosphorylation
53
Q

How is the integration of signal transduction pathways accomplished

A

through cross-regulation

54
Q

Define agonistic and antagonistic interactions with other signals

A

agonistic = additive or positive interactions
antagonistic = negative or inhibitory interactions with other signals

55
Q

Define primary cross-regulation

A

direct signaling pathways regulating shared transduction component

56
Q

Define secondary cross-regulation

A

output of one signaling pathway regulates a second signaling pathway

57
Q

Define tertiary cross-regulation

A

outputs of 2 distinct pathways exerting influence on one another

Plant Phys (15 decks)

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