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Bio 2D03 > Lecture 6 > Flashcards

Lecture 6 Flashcards

(57 cards)

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1
Q

what external signals do plants respond to?

A

temperature, wind, CO2, pathogens, water status, mineral nutrients, light levels, light quality, day length, gravity, humidity, herbivores, O2 levels in soil

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2
Q

ability to perceive light and hormones affects what developmental responses?

A

seed germination, seedling development, shade avoidance, phototropism, stomatal opening, chloroplast movements, flowering,

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3
Q

Role of light:

A

energy: photosynthesis
information: photomorphogenesis

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4
Q

photoreceptors

A

detect different wavelengths of light; photoreceptors, signal transduction pathway, response

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5
Q

skotomorphogenesis

A

light seeking response, etiolated, grow towardslight

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6
Q

etiolation:

A

hypocotyl becomes long and spindly, seedling is pale yellow (no chloroplast), apical hook forms in dicots,

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7
Q

exposure of skotomorrphogenesis plant to light

A

etiolated sidelight switches to photomorphogenesis and becomes de-etiolated

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8
Q

de-etiolation

A

chloroplast development, hypocotyl stops growing, SAM initiates leaf production

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9
Q

SAM

A

shoot apical meristem

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10
Q

phytochrome receptors:

A

apoprotein and chromophore

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11
Q

Pr phytochrome

A

chromophore absorbs red light

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12
Q

Pfr phytochrome

A

chromophore absorbs far-red light

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13
Q

phytochrome interconversion

A

in the presence of red or far red light, Pr and Pfr forms interconvert in which the chromophore undergoes a cis-trans isomerization leading to conformational change in the protein part of the phytochrome

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14
Q

R:FR

A

ratio of red to far red light which is perceived by phytochrome to elicit a response

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15
Q

phytochrome receptor functions

A

germination–small seeds with small endosperm require light to germinate

seedling establishment–etiolated to de-etiolated or non photosynthetic to photosynthetic or skotomorphogenesis to photomorphogenesis

architecture of plant–shade avoidance

initiation of flowering and seed dormancy

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16
Q

PIFs

A

polychrome interacting factors; small gene family of transcription factors

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17
Q

competitive shade avoidance response

A

grow out of shade into sunlight to promote photosynthesis, growth, and reproduction. triggered by low R:FR values because chlorophyll absorbs red light and reflects far-red light

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18
Q

features of shade avoidance response

A

growth of stem, growth of petioles, inhibition of leaf expansion, early flowering

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19
Q

Trigger of shade avoidance:

A

in shade a plant will have more Pr than Pfr because of the low R:FR indicating that reduction in active Pfr initiates shade avoidance

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20
Q

what phytochrome are involved in shade avoidance?

A

PHYB, PHYD, PHYE all act redundantly and have a major role in shade avoidance

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21
Q

PHYB

A

is a major contributor to shade response in shade and it inhibits shade response in daylight

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22
Q

PHYD and PHYE

A

contribute less to shade response in shade and they are not involved in inhibiting shade response in daylight

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23
Q

PHYB mutant arabidopsis plant

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A

shade response reduced but still observed in shade

shade responce observed in daylight

24
Q

response pathway in daylight

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A

R>FR – PHYB Pr absorbs light – interconverts to PHYB P fr – negative regulation occurs – PIFs do not facilitate shade response

25
response pathway in shade
R
26
Phototropism
directional growth towards a light source more cell growth on one side of the stem to bend it increases opportunity for light capture + photosynthesis triggered by blue light
27
PHOT1 and PHOT2 function
gene products of PHOT1 and PHOT2 are required for phototropic response, chloroplast movement and stomatal opening responses. Evidence from PHOT1&2 double mutant which failed to present any of these responses
28
Phototropic 1&2 receptors description
blue light photoreceptors with redundant functions plasma membrane associated kinase domain phosphorylates itself after blue light absorbed auxin gradient produced by higher auxin on shaded sides promoting cell elongation bending stem towards light
29
phytohormone ethylene gas functions
``` seedling germination abscission of leaves and fruits senescence of leaves and fruits response to pathogen attack regulation of fruit ripening ```
30
ethylene phytohormone in seedling development
seedling is wounded while pushing through soil, ethylene is produced, ethylene signal transduction pathway is initiated, seedling triple response occurs
31
seedling triple response
allows seedling to force its way through soil and provides protection for Shoot Apical Meristem SAM
32
features of seedling triple response
hypocotyl becomes shorter and thicker roots become shorter and thicker apical hook becomes exaggerated
33
genetic mutant screens
screen through many seedling with different but unknown mutations looking for seedlings with a specific mutant such as mutant triple response phenotype
34
etr1 mutant
no triple response when exposed to ethylene; ethylene-insensitive mutant; encodes a receptor kinase protein that binds to ethylene
35
ctr1 mutant
triple response in absence of ethylene; constitutive triple response mutant
36
ethylene stp
(signal transduction pathway) no ethylene--ethylene receptors active--activate CTR1, a negative regulator of ethylene response
37
CTR1
negative regulator of ethylene STP
38
describe what happens when ethylene is present
ethylene binds to ethylene receptors, ethylene receptors phosphorylate making them inactive. Inactive receptors are unable to activate CTR1 so CTR1 is in turn unable to inhibit the downstream ethylene STP function resulting in an ethylene response occurring
39
is ethylene response positively or negatively regulated?
the ethylene receptors negatively regulate CTR1 which negatively regulates the STP. each step is negatively regulated, however the presence of ethylene overall positively regulates the ethylene response.
40
RAN1
probably supplies ETR1 with copper ions required in ethylene binding site
41
EIN2
membrane spanning protein downstream of CTR1, function unknown
42
senescence
aging resulting in deterioration of biological function
43
what would be observed in a EIN2 loss-of-function mutant in the presence of ethylene for the seedling triple response?
because ein2 is located downstream of CTR1, loss of its function would result in the signal not being transduced causing the seedling to be unable to display the triple response. CHECK THIS ANSWER
44
temperate climate seeds
undergo maturation drying to promote dormancy and seed longevity. become dormant at end of seed development to prevent fall germination allowing overwinter. embryo survives in seed for long time without water due to seed desiccation and drought tolerance
45
tropical plant seeds
germinate as soon as seeds mature
46
ABA
abscisic acid; promotes dormancy and inhibits germination
47
GA
gibberellin or gibberellin acid; promotes: germination, mobilization of seed reserves, cell expansion in growing seedlings, glowering
48
VP1
regulates expression of ABA inducible genes during seed maturation in corn and arabidopsis
49
GA biosynthesis mutant
seeds that don't germinate
50
GA insensitive mutants
seeds that germinate poorly
51
ABA biosynthesis mutants
seeds that germinate sooner than wt
52
ABA insensitive mutants
seeds that germinate when wt does not
53
ga mutants
low GA--no germination unless GA is added
54
aba ga mutants
low GA and low ABA levels--germination occurs without adding GA
55
ratio of GA to ABA
it is a balance of GA and ABA that regulates germination, not absolute levels; GA and ABA act antagonistically
56
Outline the process from seed development to seedling development in reference to GA and ABA
- ABA promotes desiccation tolerance and dormancy - ABA is reduced and GA is increased causing dormancy to end - GA promotes reserve mobilization - GA promotes growth and cell expansion during development of seedling
57
what is actively repressing the triple response genes
Etr1 and CTR1 both actively repress the triple response genes

Bio 2D03 (10 decks)

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