Leaf Development And Evolution 3: Morphogenesis

Question 1

Size

Answer 1

Uniform growth

Question 2

Shape

Answer 2

Differential growth

Question 3

Cell expansion and division are co-ordinated to produce

Answer 3

Growth

Question 4

Growth can be anisotropic

Answer 4

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

Question 5

How do genes control leaf shape?

Answer 5

Specifying growth rates and orientations

Question 6

Progressive changes in cell division orientation in maize leaf development

Answer 6

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

Question 7

Division in maize

Answer 7

Contributes to formation of leaf sheath length

Question 8

Maize leaf general progression

Answer 8

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

Question 9

Differential gene expression regulates

Answer 9

Cell division vs expansion domains

Question 10

Late development determinants

Answer 10

Duration, rate and size

Question 11

Cell division arrest has

Answer 11

Feedback regulation at the arrest front

Question 12

Feedback regulation at the arrest front

Answer 12

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

Question 13

TCP proteins

Answer 13

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

Question 14

Basipetal

Answer 14

Tip -> base

Question 15

GRF TFs

Answer 15

Promote cell proliferation

Question 16

Complex shapes

Answer 16

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

Question 17

Lobing

Answer 17

• restricted growth in sinus?
• accelerated growth in lobe?
  Both?

Question 18

Serrations

Answer 18

Lobes + sinuses

Question 19

Lobing in A. species’

Answer 19

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

Question 20

Ectopic lobing is suppressed by

Answer 20

GA

Question 21

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

Answer 21

• GA must be suppressed

Question 22

KNOX and GA

Answer 22

• KNOX binds to GA20ox1 promotor

Question 23

stm1 dynamics

Answer 23

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

Question 24

spy

Answer 24

Constitutive GA

Question 25

Determinate

Answer 25

KNOX off, GA on

Question 26

pin1 / NPA

Answer 26

- no serrations

Question 27

PIN1 orientation

Answer 27

DR5pro + GFP

Question 28

CUC2

Answer 28

- pro + GUS - critically located to sinus - cuc2: 1x serration - initiates outgrowth orientation

Question 29

Simple leaf

Answer 29

- axillary bud part of phytomer - 4 = 4 leaves

Question 30

Compound leaf

Answer 30

- single axillary meristem to multiple leaves - develops from a single primordium - how?

Question 31

Kn1 OX in tomato

Answer 31

- super compounds!

Question 32

Model species w compound leaves

Answer 32

- Solanum lycopersicum; tomato - Cardamine hirsuta; A. relative - Pisum sativum

Question 33

Kn1 in Cardamine

Answer 33

- KO: simple - KI: super - necessary and sufficient

Question 34

Cytokinin in tomato leaves

Answer 34

- FILpro: only active in leaf primordium - AtIPT7: cytokinin biosynthesis; ^ complexity - AtCkX3: degrades cytokinin; simple!

Question 35

Compound leaf indeterminacy requires

Answer 35

Cytokinin

Question 36

Cytokinin activity is downstream of KNOX

Answer 36

- FILpro>>AtCkx3: super - 35Spro>>Kn1: complex - both; super ???

Question 37

Cytokinin is necessary for

Answer 37

Formation of extra leaflets

Question 38

PAT in Cardamine leaflets

Answer 38

- necessary for compound leaf formation - pin1 + NPA = none

Question 39

PIN1-generated auxin maxima precede leaflet formation

Answer 39

- DR5pro>>YFP

Question 40

Angiosperm evolution of compound leaves

Answer 40

- multiple independent events

Question 41

LMI1

Answer 41

- HD-ZIPI TF - suppresses KNOX @ leaf margins

Question 42

RCO

Answer 42

- 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

Question 43

rco

Answer 43

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

Question 44

What separates LMI1 and RCO?

Answer 44

- divergence in enhancer elements in promoter expression patterns

Question 45

Convergent evolution of compound leaves

Answer 45

- CUC2-auxin-PIN1-KNOX shoot module co-opted twice - Brassicales, Solanales

Question 46

Fabales

Answer 46

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

Question 47

unifoliata

Answer 47

Simple leaves

Question 48

UNI

Answer 48

- encodes pea LFY ortholog (WGD) - diverged in function by changing TF BD

Question 49

Convergent roles for KNOX and

Answer 49

LFY orthologs in compound leaf development

Question 50

Evolution of LFY function

Answer 50

- 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

Question 51

tendrilless

Answer 51

Sweet pea!

Question 52

TL

Answer 52

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

Question 53

Structure

Answer 53

1. Size vs shape 2. (In)determinism 3. Simple vs compound leaves