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Trinity Term 1 > Plant development III - Plants develop throughout their life > Flashcards

Plant development III - Plants develop throughout their life Flashcards

1
Q

Embryo development of
angiosperms

A

zygote proceeds though series of transverse and longitudinal divisions that establish axial and radial polarity.

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2
Q

Describe mutant use to study embryo development

A
  • mutants that produce seedlings that lack part of the plant body can be used to infer genetic control over the embryonic development of plant organs.
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3
Q

Describe gene modification

A

indels and substitution can determine loss of function, acquisition of a new one or abolish protein translation

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4
Q

Describe the early embryo establishment of polarity

A
  • established by vacuole/nuclear positioning
  • transmitted to the multicellular embryo via asymmetric division
  • at the 2-cell stage, polarity is maintained by auxin fluxes
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5
Q

Describe the radial development of the embryo

A

auxin induces periclinal divisions that establish radial expansion, which shifts from sink to source of auxin through the activation of biosynthetic and transport genes

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6
Q

Describe the molecular control of SAM and RAM activity

A
  • marked already in the embryo by the expression homeotic genes
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7
Q

Describe some homeotic genes

A

Wuschel and WOX

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8
Q

Describe WUS

A
  • expressed in the OC of the SAM
  • diffuses to the upper layers
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9
Q

OC

A

organizing centre

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10
Q

Describe the WUS signalling pathway

A
  • CLV3
  • CLV1/CORYN
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11
Q

Describe how the WUS signalling pathway was elucidated

A

identification of mutants with increased inflorescence and flower organ size

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12
Q

CLV3

A

CLAVATA3

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13
Q

Describe WUS and the CLAVATA genes

A
  • regulate each other (in a cell non-autonomous manner)
  • establish domains: the Organizing Centre and Stem Cell pool
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14
Q

Describe CLV3 and CLV1

A
  • CLV3: peptide hormone
  • CLV1: receptor
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15
Q

Describe gene expression in plant development

A
  • secreted peptides produced via translation and subsequent proteolytic trimming and additional modifications perceived by membrane receptors
  • initiate a phosphorylation cascade that affects gene expression
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16
Q

Describe some modifications

A
  • sulfylation
  • hydroxylation
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17
Q

Describe peptide activation

A

series of protease hydrolyses

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18
Q

Describe the stm mutation

A
  • prevents SAM maintenance
  • partly due to the activation of cytokinin biosynthesis (via the IPT gene)
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19
Q

stm

A

§shoot meristemless

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20
Q

Describe the production of primordia from the SAM

A
  • ARP genes specify primordial identity and exclude STM expression,
  • in the central zone STM prevents ARP expression
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21
Q

Describe ARP proteins

A
  • transcription factors
  • control primordium identity
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22
Q

Describe primordia localisation

A
  • depends on the existing primordia
  • activator is depleted around the primordium
  • PINs canalise auxin towards the apex of the primordial
23
Q

Describe pin mutants

A
  • fails to create primordia
  • local auxin application (shown through red fluorescent staining) induces production of a new leaf primordium
24
Q

Describe primordia budding

A
  • depends on auxin distribution
  • PINs inactivate STM expression
  • promotes proliferation and expression of ARP genes
25
Q

Describe the molecular determination of leaf shape

A
  • PIN directs auxin to form a maximum that precedes bud outgrowth
  • KNOX genes promote leaflet and lobe production
  • leaf complexity based on outgrowths is determined by the establishment of auxin maxima
26
Q

In which plant are KNOX genes studied?

A

Cardamine hirsuta

27
Q

What establishes auxin maxima?

A

PIN proteins

28
Q

Describe the establishment of leaf polarity

A
  • removal of L1 layers of cells in the primordium (abaxialisation)
  • deletion KANADI in the primordium (adaxialisation)
  • intermediate layer of WOX expression genes required for leaf blade expansion
29
Q

KANADI

A

MYB gene

30
Q

Describe establishment of leaf polarity in snapdragon

A

genetic inactivation of PHANTASTICA causes complete abaxialization.

31
Q

PHANTASTICA

A

HD-ZIP III gene

32
Q

Describe development of the RAM

A
  • main cell types of the RAM are present in the embryo
  • post-germination, RAM undergoes rapid expansion
  • subsequently balanced by the cell expansion rate
33
Q

Describe molecular regulation of the RAM

A
  • PLETHORA TFs regulate RAM identity partly by directing auxin synthesis and transport in the RAM
  • signaling peptides specify WOX5 activity in the QC that prevents differentiation of root cap cells
  • gradients
34
Q

Describe the gradients that regulate the RAM

A
  • diffusible small RNAs
  • auxin
  • diffusible TFs
  • signaling peptide gradients
35
Q

Describe the diffusible small RNAs that regulate the RAM

A

microRNA165/166 target HD-ZIP III TFs

36
Q

Describe the auxin gradients that regulate the RAM

A
  • local IAA synthesis
  • transporters: PIN efflux carriers, influx carriers
37
Q

Describe the diffusible TFs that regulate the RAM

A
  • GRAS type TFs
  • WOX-type TFs
38
Q

Describe the signalling peptide gradients that regulate the RAM

A
  • transcription/translation
  • post-translational modification
  • export
39
Q

Describe cell elongation in the elongation zone

A
  • cell wall modifying enzymes relax the cell wall
  • needs pressure turgor produced by water uptake in the vacuole
  • direction constraints by cellulose fibrils place growth perpendicularly to the growth axis
40
Q

Give a class of cell wall modifying enzymes

A

expansins

41
Q

Describe aquaporins

A

tonoblast intrinsic proteins

42
Q

Describe the differentiation zone

A
  • nutrients and water are taken up by root hairs
  • localised in the proximity of the RAM
  • travel to the xylem via the apoplast and the symplast
43
Q

apoplast

A

cell wall system

44
Q

symplast

A

cytoplasm system

45
Q

Describe the root stele

A
  • above the hair zone
  • impermeabilised by suberin enrichment in the cell walls and lignin deposition
  • forms the Casparian strip
46
Q

Describe the specification of root hair fate in the epidermis

A

diffusible signal coming from edges of cortex cells

47
Q

Describe the Casparian strip

A
  • lignification in a belt along the endodermis
  • ensured by localised deposition and polymerization of monolignols
  • directed by CASP proteins.
48
Q

Describe monolignol depositou and polymerisation

A

peroxidase and NADPH oxidases

49
Q

Describe lateral root development

A
  • pericycle cells determined by auxin peaks at intervals become initials of LRPs
  • activated at distance in the differentiation zone
50
Q

pericycle

A

External cells of the stele

51
Q

LRPs

A

lateral root primordia

52
Q

Describe formation of the LRP

A
  • auxin maxima direct anticlinal and periclinal cell divisions
  • auxin export in the above-laying cells softens their cell walls to enable penetration and emergence of the lateral root
53
Q

Most meristem types of a plant are

A

already specified in the mature embryo of angiosperms

54
Q
  • Molecular gradients (hormones, peptides, RNAs and proteins) establish functional domains that
    exclude each other
  • Shoot and root development mainly require concerted auxin and cytokinin activity
  • Leaf complexity and root meristem maintenance depend on the establishment of auxin maxima
  • Leaf and root patterning requires the intertwined activity of a large number of transcriptional regulators
A

Trinity Term 1 (38 decks)

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