Lecture 17 - Meristem development Flashcards

1
Q

What is the shoot apical meristem (SAM)?

A

A region in the growing shoot containing meristematic cells

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2
Q

What are the three parts of a shoot apical meristem? [3]

A
  • Leaf primordium
  • Apical meristem
  • Lateral branch bud
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3
Q

What are the two parts of a apical meristem? [2]

A
  • Central zone

- Peripheral zone

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4
Q

How are the cells arranged in the apical meristem?

A
  • Tunica (L1 and L2)
  • Corpus (L3)
  • Initial cells (stem cell organiser)
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5
Q

What happens to a shootmeristemless1 (STM1) mutant?

A

The shoot apical meristem is not formed

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6
Q

Where is shootmeristemless1 expressed?

A

In the shoot apical meristem

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7
Q

What happens during over expression of shootmeristemless1?

A

There are too many shot apical meristems being formed

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8
Q

What is the role of WUSCHEL in the meristem?

A
  • Expressed in meristem initial cells -

- Helps meristems to form

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9
Q

What is the role of clavata in the meristem?

A

Maintaining the meristem

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10
Q

Where are STM and WUS expressed?

A

In the central zone

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11
Q

Where is Clavata1, 3 expressed?

A

In the peripheral zone

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12
Q

What is phyllotaxy?

A

The arrangement of leaves

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13
Q

What are the ways leaves can be arranged along a stem? [6]

A
  • Alternate
  • Opposite
  • Whorled
  • Distichous (180’)
  • Descussate (90’)
  • Spiral
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14
Q

How is phyllotaxy determined?

A
  • Inhibitory field hypothesis
  • Biophysical hypothesis
  • General control of genes
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15
Q

What are two common features for the development of leaf primordia?

A
  • The position of the existing primordia are important for the position of the new primordia
  • Pre-existing primordia inhibit new primordium formation in adjacent area
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16
Q

What is the Inhibitory field hypothesis?

A

Signals from the emerging leaf primordium inhibits the formation of new new leaf primordium in the neighbouring area

17
Q

How can the formation of Primordia be induced?

A

Expansins loosen the cell wall so primordia can form there

18
Q

What happens to Auxin at low pH?

A
  • It is protonated

- Can move through the plasma membrane

19
Q

What happens to Auxin at a higher pH?

A
  • Loses the proton

- Can no longer move through the plasma membrane

20
Q

How is the charged auxin moved through the plasma membrane?

A
  • Through PIN1

- An auxin efflux carrier

21
Q

What does NPA do?

A
  • It is a auxin transporter inhibitor

- Inhibits leaf primordium formation

22
Q

What happens to a PIN1 mutant?

A

They can not form leaf primordia

23
Q

How is auxin moved within a shoot apical meristem?

A

It is moved towards a centre site

24
Q

Where is the auxin concentration at its highest?

A

Right where primordium will form

25
How does PIN1 distribution change after primordium initiation?
Changes to direct auxin flow into developing midvein
26
How does Cytokinin contribute to phyllotaxy patterning?
Sets up inhibitory fields to provide robustness in the meristem