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L3 Plant Sciences > Week 13 L3: Plant Development - Branching > Flashcards

Week 13 L3: Plant Development - Branching Flashcards

1
Q

What is an axillary bud?

A

the precursor of a branch or lateral shoot.

Formed at the junction between a leaf and the stem.

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2
Q

What are axillary buds?

A

Axillary meristems

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3
Q

What is an axillary meristem?

A

Can go on and form branches

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4
Q

What does activation of axillary meristems lead to?

A

more shoots

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5
Q

What are the axillary shoots?

A

side shoots

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6
Q

What is the structure of the axillary side shoots?

A

mimic that of the main stem

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7
Q

Do all buds form flowers?

A

no, not all buds flower

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8
Q

What determines if a bud will form a flower?

A

if it becomes active or not is highly regulated, dictates whether the plant is an ultra-branched plant or a plant with no branching

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9
Q

What is the difference between teosinte and modern corn?

A

their degree of branching

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10
Q

What type of corn has more branching?

A

ancestral maize (teosinte)

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11
Q

How would you describe a plant with limited branching with a clear central stem?

A

apically dominant over axillary shoots

apical dominance

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12
Q

What is the traditional view of what causes apical dominance?

A

an inhibitory signal from the shoot tip

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13
Q

How do we know that apical dominance is due to a signal in the shoot tip?

A

Decapitate the shoot tip and get bud outgrowth

inhibition relieved

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14
Q

Why is it advantageous to grow buds when root tip is decapitated?

A

If an animal eats the top of the plant, it can have a plan B.

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15
Q

Is decapitation followed by bud growth an example of canalise trait?

A

NO, it is an example of plasticity. As the environment changes, the plant adapts

Changing their architecture in response

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16
Q

How do you inhibits a decapitated plant from branching? Initially thought

A

Add auxin to the tip

no bud outgrowth

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17
Q

How was auxin as an axillary branch inhibitor proven wrong?

A

auxin application does not suppress axillary branching in max mutants

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18
Q

What is a max3 mutant?

A

multiple axillary branches mutant

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19
Q

How was it found that shoot and root suppress branching in max3?

A

a reciprocal experiment

a max3 shoot with a WT root
a max3 root with a WT shoot

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20
Q

What was concluded from the reciprocal experiment?

A

the branch controlling signal can be made in either tissue and can move from root to shoot

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21
Q

What is the hormone responsible for axillary bud inhibition?

A

strigalactone (SL)

22
Q

What is strigalactone?

A

a biosynthetic signalling component.

caretenoid-derived plant hormone

23
Q

How was strigalactone known?

A

From various pathogens which infect plants and plants themselves.

24
Q

What is the effect of strigalactone in max1?

A

SL treatment repressed axillary bud outgrowth in mutants. As the inhibitory SL is added so branch growth is less that max 1 with control.

25
Q

What is the relationship between strigolactone and auxin?

A

auxin up-regulates SL synthesis

26
Q

Are SLs conservered?

A

YES

27
Q

What hormones promote shoot outgrowth?

A

cytokinin in the meristem

28
Q

How does auxin regulate strigolactone?

A

stimulates CCD7 AND CCD8 to activate SL which inhibits bud growth

29
Q

How does auxin inhibit cytokinin?

A

it inhibits IPT which usually stimulates cytokinin to stimulate bud growth

30
Q

How does auxin inhibit cytokinin?

A

it inhibits IPT which usually stimulates cytokinin to stimulate bud growth

31
Q

Does auxin directly inhibit bud growth too?

A

yes

32
Q

Where is auxin located?

A

shoot tip SAM

33
Q

Where is strigolactone located?

A

Root tip meristem

34
Q

Where is cytokinin located?

A

root rip meristem

35
Q

What abiotic factors inhibit branching?

A

low light

high density

36
Q

What abiotic factors promote branching?

A

sugars and fertiliser

37
Q

What are other repressor mutants in plants for shoot branching?

A

BRC 1 and 2

38
Q

What kind of mutants is ycc1?

A

auxin over-producing mutant

39
Q

What are all the mutant types of branching?

A

brc1
yyc1
max1

40
Q

How do you set up a qPCR experiment?

A

BRC1 gene with an endogenous control gene between species.
Allow to compare genotypes between individuals

e.g. ACTIN8

41
Q

What is the purpose of the qPCR?

A

compare levels of BRC1 in brc-1, max mutants and ycc1

42
Q

What were the levels of BRC1 mRNA in max mutants?

A

low, as the mutant of max is defective in the strigolactone gene so will be branching. Thus low levels of branching inhibitory gene (low BRC1)

43
Q

What are levels of BRC1 in yyc1 branching mutants like?

A

ycc1 overproduce auxin so will have very little branching this high levels of BRC1 which inhibits branching

44
Q

What does a BRC mutant cause to plant branching?

A

Highly branched

45
Q

What does this tell us about hormone signalling pathways?

A

The hormone signalling pathways signalling the expression of these genes in the axillary but and that is correlating to whether that bud is active or not.

46
Q

What causes apical dominance in maize?

A

up-regulation of single gene, teosinte branched 1 (Tb1), encoding a TCP transcription factor - an orthologue of branched1/2 in arabidopsis.

47
Q

What are the similar mutants in arabidopsis and maize which cause a decrease in branching?

A

maize: Tb1 mutant
arab: BRC1 mutant

48
Q

Why does the upregulation of Tb1 mutant cause an apical architecture?

A

As it encodes TCP TF which acts like BRC1&2 to decrease axillary branching and cause an apical structure.

growth and little branching

49
Q

What are the inhibitoey branching hormones?

A

MAIZE: Tb1
Arab: BRC1/2

50
Q

What does a plant look like which has a mutant version of Tb1/BRC1?

A

Lots of leaves

BEACUSE the mutant hormones are not repressing branching.

L3 Plant Sciences (17 decks)

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