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w Biology of Regeneration > 2. Plant regeneration > Flashcards

2. Plant regeneration Flashcards

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1
Q

How has plants’ ability to regenerate been exploited in industry?

A

Plant regeneration properties - microporpagation - can regenerate whole body from individual tissues -> most plant cells are totipotent

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2
Q

Explain plant in vitro regeneration

A

In vitro regeneration - process of regenerating a whole plant from a certain tissue - placed in nutrient-rich medium - process relies on the inherent totipotency of plant cells = plant cloning

Explant takne - sterilized - placed into nutrient rich medium - added hormones auxin and cytokinin - explant dedifferentiates - forms callus (mass of unorganized cells) - organogenesis -> plantlet

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3
Q

What types of plant cells exist?

A
  • Zygote: only embryonic stem cell - only totipotent stem cell

Specified in specific niches:
- Root meristem
- Shoot meristem

Apical / lateral meristems

Additional cambial stem cells - produce phloem and xylem tissues in secondary growth

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4
Q

Explain the structure of root meristem

A

Consists of non-stem cells, stem cells and organizing center (OC) = quiescent center

Highly regulated signalling to maintain cells in different pluripotency states

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5
Q

Explain the structure of shoot meristem

A

Consists of the bud - in the center central zone (CZ) + peripheral zone (PZ)

CZ - slowly dividing reservoir of stem cells - self-renew + differentiate cells into PZ
PZ - more differentiated, more rapidly dividing cells - eventually differetiate into organs

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6
Q

Are the same genes used for root and shoot meristem maintenance?

A

No, genes for root and shoot meristem formation and maintenacne are related but not identical

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7
Q

Explain what are cambial stem cells

A

Cambial stem cells - in cambium - thin layer of meristematic tissue between the xylem and phloem in vascular plants - conatin xylem and phloem precursors - develop in secondary growth - cambial stem cells have indeterminate growth - can continue dividing through lifetime

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8
Q

What is plant secondary growth

A

Secondary growth - increases the diameter of the stem and root - cambial stem cells are responsible for the secondary growth

This is different from primary growth, which increases the length of the plant and is driven by the apical meristems

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9
Q

What is plant primary growth

A

Primary growth - increases the length of the plant and is driven by the apical meristems

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10
Q

Why is the definition of toti/pluripotency with respect to regeneration so vague in plants?

A

Definition of toti/pluripotency with respect to regeneration so vague in plants because stem cells in plants are organised differently than animals - normally niche specific stem cells don’t perform totipotency but they can if need to (micropropagation)

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11
Q

Do plant tissue stem cells have similar function to animal tissue stem cells?

A

No, in plants niche specific stem cells can become any other tissue - animal stem cells are confined to the niche

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12
Q

Why lifestyle is an important consideraition when reflecting on different “nature” of stem cells in different phyla and kingdoms?

A

Because plants don’t move - are expected to regenerate what they loose - need oto change capacity, not damage

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13
Q

What are the two types of regeneration trajectories that reveal regenerative capacity of a plant?

A

Regeneration after trauma
- maintain tissue context
- from single, isolated cells

Regeneration without trauma

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14
Q

Explain plant regeneration without trauma

A

Plant regenerationw without trauma:
- plant development - indeterminate - # of organs not pre-determined
- in perennial plants growth resumes after dormancy periods
- this regeneration mediated by apical and lateral meristems and re-capitulates organogenesis and ifferentiation from embryogenesis
=> this is not regeneration - normal plant lfie

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15
Q

Explain plant regeneration after trauma

A

Regeneration after trauma:
- several plant vascular tissues resume proliferation and replace severed connection
- distinct vascular cells undergo trans-differentiation into missing vascular cells
- other cell types can resume division but produce scar tissue but not regenerate

BUt trauma in root meristems dealt differently

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16
Q

Explain the role of PIN1

A

PIN1 - auxin transporte in plant cekks

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17
Q

What role does PIN1 play in regeneration

A

Pin1 - tranpsoter - tranpsortes sxin
- auxin directionally transported to repair wounded tissue

18
Q

What is the pathway triggered in plant wounding

A
19
Q

Would plants be able to regenerate if their stem cell niches were compromised?

A

Yes, stem cell niches would be restored by new cells - mechanism must be ensured because if get severely daamaged cause can’t move to escape

20
Q

What drives root stem cell niche regeneration?

A

Root stem cell niche (SCN) regneration driven by not only by root SCN genes

21
Q

What is the role of plant stem cells in tissue repair and maintenance?

A

Tissue repair: plant stem cells regenerate even if stem cell niche cut off

Maintenance: stem cells maintained by meristems - stem cell niches - stem cells divide and produce new cells

=> plant stem cells not needed for rgeneration - they can dedifferentiate to become stem cells - with only one condiiton - need to be closer to the tip thn 200um - otherwise lost potential to dedifferentiate into stem cells

22
Q

Which cell types are involved in tissue repair?

A

Tissue repair is done by the cells of the tip - up ot 200um from the tip - still have the capacity to dedifferentiate and give rise to new cell types

23
Q

How does auxin flux contribute to repair of severed vascular tissues?

A

When tissue damaged - directional auxin transport to the site - new vasculature differentiates

24
Q

Why can the root tip regenerate even if all stem cells are excised?

A

Bceause plant cells are pluripotent - can dedifferentiate and redifferentiate into a new cell type to replace the lost - this mechanism evolved because plants are not dynamic - can’t run way form predators - need good regeneration systems to survive

25
Q

Explain what is lateral root development

A

Lateral roots grow out from the primary root - develop from pericycle cells - layer of cells found just inside the root endodermis, adjacent to the vascular tissues (xylem and phloem)

26
Q

What is callus?

A

Plant callus - mass of undifferentiated, proliferating cells - forms when plant tissues are subjected to certain conditions - particularly in response to wounding or during in vitro culture

27
Q

How is callus formation related to lateral root development?

A

These two processes use similar pathway - callus initiates a regeneration pathway similar ti lateral root development

28
Q

Explain the mechanism of callus formation

A

Callus resembles tip of root meristem - callus formation requires lateral root genetic programme - depending on auxin level lateral root growth vs callus formation - strong auxin triggers regeneration (callus) - weaker auxin lateral root formation

29
Q

Explain callus induction experiments in vitro

A

Callus induction by genetic experiment
- alf4-1: wt, het, homo -> alf4-1 needed for root development - otherwise callus
- ABA +/- -> similar results - doesn’t affect callus induction - no mersitem activation in callus formation

In callus formation - a blob formed
In root growth - directional growth

But overall callus formation requires laetral root genetic programme - auxin signalling

30
Q

Do all plant cells regenerate by callus formation?

A

No, only those tissues which have lateral root growth ability - others dedifferentiate and respecify into the needed tissue

31
Q

What are the barriers to plant regeneratino?

A

Barriers to plant regeneration:
- epigenetic: does epigenetic modification change inn regeneration
- ploidy: are all cells of all ploidy equally competent to regenerate

32
Q

What is required to form shoot from callus tissue

A

Epigenetic changes are needed - specifically in WUS gene

33
Q

Plants are not observed to form tumours, what are the mechanisms that block this?

A

Plants don’t get cancer because of epigenetic specifics + cell divisions very controlled + have more DNA damage response genes

Also, elephants, even tho larger and higher chance of cancer - don’t get cancer as oftne as expected becaus have more DNA damage response genes

34
Q

Explain the significance of the finding that all callus, irrespective of the tissue of origin, goes through a developmental pathway resembling lateral root development

A

Lateral leaves, lateral roots take different mechanisms to grow but callus formation which used lateral root growth mechanism is done both in leaves and roots - ??

35
Q

What does it tell you about the origin of organising centre of a callus with respect to its cell types

A

??

36
Q

What is endoreplication?

A

Endoreplication - modified cell cycle - cell undergoes DNA replication without subsequent cell division - increase in the cell’s nuclear DNA content - polyploidy

37
Q

How are endoreplication and trichome formation related?

A

Endoreplication is a natural process in differentiated plant cells - BUT endoreplication may prevent regeneration from all plant cell types

-> suppression of endoreplication prevents differentiation and/or maintenance of differentiation pathway for trichomes - transformation into trichomes can’t be sustained

Low ploidy is aborting trichomes
===> endoreplication drives trichome formation

38
Q

Is endoreplication a barrier to regeneration in differentiated cells?

A

Yes, the mor eendreplication the more restricted/locked in the dfferentiated state - loss of division potential, terminal differentiation

only can be reversed in case of wounding / hormonal signalling

read more

39
Q

Regeneration in plants summary

A
40
Q

How could it be proved that endoreplication is a barrier to plant cell regeneration in toher tissue contexts?

A

Create inducable deletions of endoreplication genes -> edit non-regenerating cells to see if would regenerate

41
Q

How could it be proved that non-pericycle like cells are not capable of regeneration?

A

Try over-expressing needed genes for regeneration

42
Q

Does the statement that endoreplicated cells are unable to regenerate contradict the finding that leaf margin cells are able to resume division after trauma?

A

Did’nt form callus - different callus type - not all can form any tissues

Callus = scar tissue in this case

?? read

w Biology of Regeneration (7 decks)

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