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Trinity Term 1 > Plant development IV - Epigenetics and plant reproduction > Flashcards

Plant development IV - Epigenetics and plant reproduction Flashcards

1
Q

Why is flowering advantageous?

A
  • pollinator attraction
  • increased fertilisation chances
  • further development (fruit) allows improved seed dispersal
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2
Q

Describe the promoters of the floral transition

A
  • hormonal signalling
  • light quality
  • photoperiod
  • warm temperature
  • nutrients
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3
Q

Describe enablers of the floral transition

A
  • vernalisation
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4
Q

Characterise a plant’s life cycle

A
  • adulthood
  • insensitive phases
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5
Q

Describe adulthood in plants

A

stage at which the SAM is receptive to flowering stimuli

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6
Q

Describe what allows the transition to adulthood in plants

A

sugar levels in the leaf stimulate expression of a microRNA that inhibits a class of TFs

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7
Q

What is leaf sugar quantity a measure of?

A

amount reserved for reproduction

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8
Q

What might stop a plant from flowering?

A
  • cold
  • stress
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9
Q

Describe circadian rhythms - the basics

A

oscillations of biological parameters within a 24h period, entrained by exogenous cues

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10
Q

Describe circadian rhythms - the specifics

A
  • environmental inputs lead to entrainment pathways
  • circadian gating of entrainment and outputs
  • circadian oscillation
  • output pathways
  • changes in gene rhythm of transcription, physiology and biochemistry
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11
Q

Describe short-day plants

A

flower when an uninterrupted period of darkness exceeds a critical night length

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12
Q

Describe long-day plants

A

flower when a period of darkness is less than a critical night length threshold

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13
Q

Which wavelengths of light promote flower transitions?

A

red (via phytochromes) and blue (via FKF1)

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14
Q

FKF1

A

LOV-domain containing photoreceptors

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15
Q

Describe the doincidence model of plant response to light change

A

plant should be receptive.on circadian bases, to the floral light stimulus
- internal clock sets the light sensitivity of the plant

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16
Q

How do plants perceive the photoperiod?

A
  • Pr is synthesised
  • Pr becomes Pfr on exposure to red light
  • Pfr either goes to enzymatic destruction, or is slowly converted to darkness (under far-red light)
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17
Q

How is light and temperature detected by a plant?

A

phytochrome B

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18
Q

Describe active phytochrome B

A
  • represses floral transition in Arabidopsis
  • 27°C stimulates reversion to the inactive form
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19
Q

Describe the relationship between phyB and temperature

A

positively correlated (not linear).

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20
Q

Give examples of day-neutral plants

A
  • Phaseulus vulgaris
  • Abronia villosa
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21
Q

Describe day-neutral plants

A
  • species adapted to live at tropical/equatorial latitudes where day and night length does not change
  • species that need to flower when conditions are permissive
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22
Q

Describe the hormonal control of flowering

A
  • gibberellin-deficient mutants exhibit delayed flowering, dependent upon DELLA proteins
  • long-day photoperiods induce an increase in active GA levels.
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23
Q

List some GAs

A

GA1, GA8, GA20

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24
Q

Describe the effect of long photoperiods on GA1

A

500%. change

25
GA1
active GA, responsible for growth
26
Describe the effect of long photoperiods on GA8
1450% increase
27
GA8
inactive GA1 metabolite
28
Describe the effect of long photoperiods on GA20
1700% increase
29
GA20
inactive GA1 precursor
30
Describe plants under long day (LD) conditions
- spraying leaves with GAs accelerates flowering - promoting catabolism of active GAs in the SAM or vasculature inhibits flowering
31
Describe plants under short day (SD) conditions
Promoting catabolism of active GAs in the SAM (not in the vasculature) inhibits flowering.
32
How have grafting experiments been used in plant development
reveal the existence of a transmissible signalling molecule able to promote flowering
33
Describe the florigen
- moves with a speed of approx 50 cm h-1 - in the phloem
34
FT
florigen protein
35
Describe FT
- produced in the leaf vasculature - travels to the phloem to induce SAM conversion to inflorescence meristem and induction of bract primordia
36
Describe the molecular function of FT
- once in the SAM, forms a complex with FD and 14-3-3 - induces expression of floral meristem identity genes - complex represses FD expression in a feedback loop
37
FD
a TF
38
14-3-3
adaptor protein
39
Give a gene that codes for floral meristem identity
APETALA1
40
Describe the transcriptional control of FT
- autonomy - vernalisation - warm temperature - photoperiod and clock
41
Describe the transcription level of the FT gene
- controlled by two main regulators: FLC and CO - integrate several regulatory pathways
42
FLC
- flowering locus C - repressor - upstream of CO
43
CO
- constans - activator - downstream of FLC
44
Give a molecular explanation of the coincidence model
- the circadian clock and light regulate the CO transcriptor - light signals regulate CO protein stability - transcriptional and post-translational regulation enable CO (and thus FT) accumulation in LD conditions only
45
Describe coincidence in rice
- Hd1 represses the florigen signal - SD is required for flowering
46
Hd1
CO ortholog
47
Describe the vernalisation pathway
- required due to high FLC activity in and after germination - vernalisation silences FLC
48
How is vernalisation effects studied?
flc mutants appear the same as an annual winter ecotype post-vernalisation
49
Describe the epigenetic control of vernalisation
- FLC locus regulated by alternative histone modifications shifting chromatin locally from an open to a closed state - regulatory small RNA produced at the FLC locus control the mRNA level
50
How is FLC expression reset in the embryo
- PRC2 complices trimethylates the Lys-27 residue of H3 (silencing) - PRC1 complex monoubiquitinates H2A, stably repressing expression - trithorax trimethylates Lys-4 of H3; induces the expression of target loci - during fertilisation, LEC1 complex opens FLC chromatin again
51
Describe FT control of tubers in potatoes
- FT identity conserved among solanaceae - grafting a scion on potato rootstock causes Mobile Flowering signal to induces tuberisation - meristematic activity of potato stolons is under photoperiodic control of a CO/FT couple - flowering and tuberisation are coordinated
52
scion
flowering tobacco
53
How can flowering time be controlled by humans?
- EID1 variant induced late flowering and more chlorophyll in long days - seen in domestiction of wild tomato from Mesoamerica to northern latitudes - spread of barley from the fertile crescent: winter barley to spring barley
54
EID1
light signalling
55
winter barley
photoperiod sensitive
56
spring barley
- prr7 mutant - insensitive to the photoperiod
57
Describe sugarbeet breeding
for seed/sugar production
58
Describe sugarbeet
- biennial crop cycle - flowers and root compete for sugars - seed production is preferably annual - global warming prevents flowering
59
Combined effect of global warming and night lighting may
induce premature flowering or delayed senescence.

Trinity Term 1 (38 decks)

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