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B3.0 > Principles In Plant Development > Flashcards

Principles In Plant Development Flashcards

1
Q

Angiosperm development

A
  • low degree of tissue specialisation
  • high degree of tissue plasticity
  • organogenesis occurs throughout life @ meristems
  • rigid cell walls; morphogenesis occurs by differential growth, not cell movement
  • permanently rooted; and environment profoundly affects development
  • no permanent germline
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2
Q

Can predicable fate maps be determined?

A
  • Clonal analysis
  • The each spikelet pair is derived from a single cell
  • looking for patterns of shared mutation (e.g. virescence)
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3
Q

Induce sectors in mature maize embryo

A
  • irradiation creates random change
  • where is it?
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4
Q

Sector size in mature maize plant

A
  • grow the plants (1000s)
  • 18 leaves, tassel and ear
  • score where the green sectors are in the field
  • no compartments, overlap
  • no rigid fate map; plasticity
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5
Q

‘Fate map’ of embryonic maize meristem

A
  • first 5 leaves initiated @ embryogenesis
  • probability map
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6
Q

Assess growth plasticity

A

1) grow
2) remove leaves
3) place apex back in culture
4) count leaves that form
- plastic: more meristems would form
- time-shift assay

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7
Q

Are cells “used up” in the meristem?

A
  • “depleted” meristem produces entire set of leaves
  • probability, but not predictability
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8
Q

Is cellular differentiation lineage or position dependent?

A

Good q!

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9
Q

Maize leaf anatomy

A
  • C4
  • bundle sheath + mesophyll cells
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10
Q

white deficiency and ring chromsomes

A
  • a more contrived sector analysis
  • ring chromosomes contain wt gene copy (spontaneous loss during mitosis)
  • homozygous mutation on autosome: cells are white
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11
Q

Sectors of chlorophyll fluorescence

A
  • where is the white tissue in the cross-section?
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12
Q

Sector types

A
  • sectors are undermine about lineage relationships in leaf (3 layers)
  • indicates timing of mutation
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13
Q

Distinct cell types share a cell lineage

A
  • one internal cell divides to form a middle layer
  • middle layer forms all BS and mesophyll cells
  • positional
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14
Q

Indeterminate growth

A

Shoot/root

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15
Q

Determinate growth

A

Leaf, lateral root, floral organ

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16
Q

What regulates the switch from indeterminate to determinate growth?

A

Knotted1 gain of function promoter mutation in maize (Kn1)

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17
Q

Kn1

A
  • “knots” of indeterminate growth on the leaf due to ectopic expression
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18
Q

GOF

A
  • dominant genes can’t tell you what a gene is necessary for
  • you need a LOF recessive gene
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19
Q

Kn1 expression

A
  • in meristem, not leaves
  • isn’t switched off
  • causes aberrant division
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20
Q

KNOX in Arabidopsis

A
  • 35S constitutive promoter
  • KNAT1 = ortholog
  • Homeobox
  • LOF: shootmeristemless
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21
Q

Sufficiency experiments

A

Express a gene ectopically

22
Q

KNAT1

A
  • ectopic expression gives extra division; lobing
23
Q

What regulates organ formation?

A

Auxin gradients

24
Q

Auxin gradients in organ primordia

A
  • auxin responsive DR5 pro motor driving fluorescent reporter gene expression
  • watch organogenesis
  • proto-leaves maxima
25
Q

NPA on organs

A
  • no leaves
  • PIN-like fluorescence
26
Q

Discrete auxin foci allow

A

Organ formation

27
Q

PIN proteins

A
  • mutants = pin
  • localise to one side, outgrowth direction
28
Q

To what extent to changes in cell division planes alter morphogenesis?

A

tangled maize mutants have aberrant cell divisions

29
Q

tangled

A
  • ‘messy’ epidermal cells
  • leaves feel papery
30
Q

Quantify division plane direction in tangled mutants

A
  • transverse divisions are completely random
31
Q

tangled morphology

A
  • normal shape
  • smaller, crinklier
  • supracelullar control to balance/check
32
Q

To what extent to cells act cell-autonomously?

A
  • Sector induction in Kn1 mutant maize plants
  • does Kn1 only act where it is expressed?
33
Q

Sector induction in Kn1 mutant maize plants

A
  • genetic mosaic analysis; removing a gene product
  • wt: green
  • homozygous recessive: white
  • irradiate and look for white sectors
34
Q

Sector types in Kn1

A
  • knots on epidermis correlate with expression of mutant allele in central leaf domain
  • gene is only sufficient to make knots if it is expressed in middle layer
  • TFs move cell-> cell via plasmodesmata
35
Q

Kn1 TFs and plasmodesmata

A
  • usually: 2kDa limit
  • these are 60
  • mechanism unknown
36
Q

Accumulation of Kn1 gene products

A
  • Ab localisation
  • protein, but not mRNA accumulates in the epidermis
  • not expressed here
37
Q

Accumulation of Kn1 gene products

A
  • Ab localisation
  • protein, but not mRNA accumulates in the epidermis
  • not expressed here
38
Q

Confirming Kn1 protein mobility

A
  • fuse to a fluorescent tag and object: moves out
  • control tag stays in
39
Q

Root development in legumes

A
  • changes in presence of bacteria and fungi
40
Q

Root development in legumes process

A
  • molecular signals initiate the interactions
  • plant root exudates: flavonoids, strigolactone
  • Rhizobia: nod factor
  • fungi: myc factor
  • root redifferentiates at site of perception into nodules
41
Q

Nodules

A
  • Complex vascular network
  • pops of bacteria
42
Q

nod factors

A
  • bind to cell-surface RLKs
  • ligand recognises binding domain
43
Q

RLKs

A
  • ligand binding activated internal kinase domain
  • downstream phosphorylation
  • most interacts w / environmental cues
44
Q

Downstream of RLKs (NFR115)

A
  • membrane depolarisation due to early ion fluxes
  • root tip swelling
  • SYMRK induces calcium fluctuations/relocalisation/spiking (RLK, MLK cascades)
  • TF induction for new developmental programme
  • root hair curling, NIN activation
  • infection thread formation
  • nodule organogenesis
45
Q

Gametophyte

A
  • multicellular
  • contains gametes
46
Q

Ovule

A
  • somatic tissue
  • megaspore mother cell specification
  • meiosis: haploid tetrad (3x degenerate)
  • remaining divide mitotically to form 8x nuclei
  • one doesn’t divide: 7 cells
  • this is the multicellular gametophyte
47
Q

Anther

A
  • microscopic mother cell goes thru meiosis to form tetrad
  • mitosis forms pollen grains
  • 2x sperm nuclei
  • 1x degenerative cell
48
Q

Genes that restrict sporophyte no to remain discrete

A
  • lead to more mega/microspore mother cells
  • small peptides
  • RLKs
  • specified cell initiates a communication cascade w/ neighbouring cells to inhibit them from becoming mother cells
49
Q

What distinguishes germline from somatic tissues?

A
  • neighbour differentiation
  • epigenetic marks on megaspore mother cell goes
50
Q

Epigenetic marks on megaspore mother cell

A
  • total heterochromatin volume >
  • H8 mother cell specification
  • H1 neighbouring cells

B3.0 (23 decks)

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