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B3.0 > Leaf Development And Evolution 3: Morphogenesis > Flashcards

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
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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
Q

Determinate

A

KNOX off, GA on

26
Q

pin1 / NPA

A
  • no serrations
27
Q

PIN1 orientation

A

DR5pro + GFP

28
Q

CUC2

A
  • pro + GUS
  • critically located to sinus
  • cuc2: 1x serration
  • initiates outgrowth orientation
29
Q

Simple leaf

A
  • axillary bud part of phytomer
  • 4 = 4 leaves
30
Q

Compound leaf

A
  • single axillary meristem to multiple leaves
  • develops from a single primordium
  • how?
31
Q

Kn1 OX in tomato

A
  • super compounds!
32
Q

Model species w compound leaves

A
  • Solanum lycopersicum; tomato
  • Cardamine hirsuta; A. relative
  • Pisum sativum
33
Q

Kn1 in Cardamine

A
  • KO: simple
  • KI: super
  • necessary and sufficient
34
Q

Cytokinin in tomato leaves

A
  • FILpro: only active in leaf primordium
  • AtIPT7: cytokinin biosynthesis; ^ complexity
  • AtCkX3: degrades cytokinin; simple!
35
Q

Compound leaf indeterminacy requires

A

Cytokinin

36
Q

Cytokinin activity is downstream of KNOX

A
  • FILpro»AtCkx3: super
  • 35Spro»Kn1: complex
  • both; super
    ???
37
Q

Cytokinin is necessary for

A

Formation of extra leaflets

38
Q

PAT in Cardamine leaflets

A
  • necessary for compound leaf formation
  • pin1 + NPA = none
39
Q

PIN1-generated auxin maxima precede leaflet formation

A
  • DR5pro»YFP
40
Q

Angiosperm evolution of compound leaves

A
  • multiple independent events
41
Q

LMI1

A
  • HD-ZIPI TF
  • suppresses KNOX @ leaf margins
42
Q

RCO

A
  • 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
Q

rco

A
  • simples leaves
  • is it inhibiting KNOX? No; non-statistical expression difference; no interaction
  • is it inhibiting PIN1? No.
  • proliferation in sinuses
44
Q

What separates LMI1 and RCO?

A
  • divergence in enhancer elements in promoter expression patterns
45
Q

Convergent evolution of compound leaves

A
  • CUC2-auxin-PIN1-KNOX shoot module co-opted twice
  • Brassicales, Solanales
46
Q

Fabales

A

3 different leaves:
- stipule
- leaflets
- tendrils
- no KNOX

47
Q

unifoliata

A

Simple leaves

48
Q

UNI

A
  • encodes pea LFY ortholog (WGD)
  • diverged in function by changing TF BD
49
Q

Convergent roles for KNOX and

A

LFY orthologs in compound leaf development

50
Q

Convergent roles for KNOX and

A

LFY orthologs in compound leaf development

51
Q

Evolution of LFY function

A
  • 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
52
Q

tendrilless

A

Sweet pea!

53
Q

TL

A
  • LMI1 ortholog
  • suppressed growth @ leaf margin in A.
  • expressed throughout tendril primordia in situ hybridisation for P. sativum
  • specifies tendril, not leaflet

B3.0 (23 decks)

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