Leaf Development And Evolution 3: Morphogenesis Flashcards

1
Q

Size

A

Uniform growth

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2
Q

Shape

A

Differential growth

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3
Q

Cell expansion and division are co-ordinated to produce

A

Growth

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4
Q

Growth can be anisotropic

A
  • orientation; different structure
  • must be specified
  • simple principles lead to different shapes
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5
Q

How do genes control leaf shape?

A

Specifying growth rates and orientations

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6
Q

Progressive changes in cell division orientation in maize leaf development

A
  • early: isotropic
  • P5: division in base and upper middle are oriented
  • at the tip: just expansions
  • P7: expansion thru majority of leaf
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7
Q

Division in maize

A

Contributes to formation of leaf sheath length

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8
Q

Maize leaf general progression

A

1) wide structure: primordial encircle meristem
2) transition to longer structure
3) v. long and narrow
- all achieved by changes in orientation and division cessation from tip -> base

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9
Q

Differential gene expression regulates

A

Cell division vs expansion domains

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10
Q

Late development determinants

A

Duration, rate and size

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11
Q

Cell division arrest has

A

Feedback regulation at the arrest front

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12
Q

Feedback regulation at the arrest front

A
  1. TCP proteins
  2. miRNAs reinforce boundary
  3. Arrest front moved basipetally
  4. Cell division -> expansion
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13
Q

TCP proteins

A
  • promote cell expansion
  • activate in expanding part of leaf
  • activate miRNA396
  • GRF inhibited
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14
Q

Basipetal

A

Tip -> base

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15
Q

GRF TFs

A

Promote cell proliferation

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16
Q

Complex shapes

A
  • serrations, lobing
  • arise from persistent growth in isolated blade regions
  • superimposition
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17
Q

Lobing

A
  • restricted growth in sinus?
  • accelerated growth in lobe?
    Both?
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18
Q

Serrations

A

Lobes + sinuses

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19
Q

Lobing in A. species’

A
  • associated w STM activity in leaf
  • high: distinct lobes emerge from central petiole
  • complexity spectrum
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20
Q

Ectopic lobing is suppressed by

A

GA

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21
Q

For the indeterminacy that leads to proliferation of lobing to be enabled

A
  • GA must be suppressed
22
Q

KNOX and GA

A
  • KNOX binds to GA20ox1 promotor
23
Q

stm1 dynamics

A
  • stm1
  • weak stm1: small meristem; some indeterminate growth
  • weak stm1 + spy : growth abolished
  • STM has to turn GA20ox1 off
24
Q

spy

A

Constitutive GA

25
Determinate
KNOX off, GA on
26
pin1 / NPA
- no serrations
27
PIN1 orientation
DR5pro + GFP
28
CUC2
- pro + GUS - critically located to sinus - cuc2: 1x serration - initiates outgrowth orientation
29
Simple leaf
- axillary bud part of phytomer - 4 = 4 leaves
30
Compound leaf
- single axillary meristem to multiple leaves - develops from a single primordium - how?
31
Kn1 OX in tomato
- super compounds!
32
Model species w compound leaves
- Solanum lycopersicum; tomato - Cardamine hirsuta; A. relative - Pisum sativum
33
Kn1 in Cardamine
- KO: simple - KI: super - necessary and sufficient
34
Cytokinin in tomato leaves
- FILpro: only active in leaf primordium - AtIPT7: cytokinin biosynthesis; ^ complexity - AtCkX3: degrades cytokinin; simple!
35
Compound leaf indeterminacy requires
Cytokinin
36
Cytokinin activity is downstream of KNOX
- FILpro>>AtCkx3: super - 35Spro>>Kn1: complex - both; super ???
37
Cytokinin is necessary for
Formation of extra leaflets
38
PAT in Cardamine leaflets
- necessary for compound leaf formation - pin1 + NPA = none
39
PIN1-generated auxin maxima precede leaflet formation
- DR5pro>>YFP
40
Angiosperm evolution of compound leaves
- multiple independent events
41
LMI1
- HD-ZIPI TF - suppresses KNOX @ leaf margins
42
RCO
- LMI1 duplicate - lost in secondarily simple brassica (A. Thaliana) - retained in complex brassica (C. hirsuta, A. lyrata) - expression shown by promotor GUS reporter transgenic - in margins + stipules of C. hirsuta - inhibits cell proliferation in sinuses
43
rco
- simples leaves - is it inhibiting KNOX? No; non-statistical expression difference; no interaction - is it inhibiting PIN1? No. - proliferation in sinuses
44
What separates LMI1 and RCO?
- divergence in enhancer elements in promoter expression patterns
45
Convergent evolution of compound leaves
- CUC2-auxin-PIN1-KNOX shoot module co-opted twice - Brassicales, Solanales
46
Fabales
3 different leaves: - stipule - leaflets - tendrils - no KNOX
47
unifoliata
Simple leaves
48
UNI
- encodes pea LFY ortholog (WGD) - diverged in function by changing TF BD
49
Convergent roles for KNOX and
LFY orthologs in compound leaf development
50
Evolution of LFY function
- Physcomotrella: induces first division in zygote; needed for proliferation - Seratroptris ricardii: maintains activity of single apical cells required for leaf formation; needed for divisions - angiosperms: promotes in->det
51
tendrilless
Sweet pea!
52
TL
- LMI1 ortholog - suppressed growth @ leaf margin in A. - expressed throughout tendril primordia in situ hybridisation for P. sativum - specifies tendril, not leaflet