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BIOL 3542 > Final Exam - Plant Development > Flashcards

Final Exam - Plant Development Flashcards

1
Q

Arabidopsis thaliana

A
  • a model for plant development
  • common name: canola
  • picked due to its genetics, small, easily grown in lab, short generation time (faster than mice)
  • genome has been sequenced
  • development relatively simple
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2
Q

Root apical meristem

A
  • Plants generate new tissue through stem cell populations called root and shoot apical meristems (SAM)
  • Undifferentiated stem cell population
  • Formed by the heart stage of development
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3
Q

Shoot apical meristem (SAM)

A
  • Plants generate new tissue through stem cell populations called root and shoot apical meristems (SAM)
  • Undifferentiated stem cell population
  • Formed by the heart stage of development
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4
Q

Cambium

A

-a ring of meristem in the stems of plants that gives rise to new stem tissue, which increases the diameter of the stem

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5
Q

Periclinal

A

-describes cell divisions in a plane parallel to the surface of the tissue

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6
Q

Heart stage

A
  • a stage in embryogenesis in dicotyledonous plants in which the cotelydons and embryonic root are starting to form, giving a heart-shaped embryo
  • meristem regions have formed by this stage
  • During maturation, following the heart stage, cells expand to allow for growth rather than divide
  • Start to express genes that allow for accumulation of energy reserves such as starch
  • root and shoot apical meristems are formed by this stage
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7
Q

Torpedo stage

A
  • Maturation of the embryo at the torpedo stage onward is largely due to cell expansion
  • Plant cell wall breakdown and rebuilding
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8
Q

Cambium

A
  • stem radial growth
  • distinct secondary stem cell population
  • ring of stem cells
  • a ring of meristem in the stems of plants that gives rise to new stem tissue, which increases the diameter of the stem
  • is a secondary meristemic tissue and allows for radial growth (Most plant structures are generated by meristems with the deception of stem growth)
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9
Q

FASS gene

A
  • Mutation results in a disordered pattern of cell division in the embryo
  • FASS mutants fail to produce microtubules pre-prophase which would predict the plane of cell division
  • But in Fass mutants all cell types were still present in the embryo
  • Suggests that precise cell division is not required for pattern formation in the embryo
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10
Q

Cell division patterns

A
  • precise cell division is not required for pattern formation
  • Cells can divide in two directions
    a. Parallel to the radial axis (periclinal)
    b. Right angles (anticlinal)
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11
Q

Periclinal

A
  • parallel to the radial axis

- describes cell divisions in a plane parallel to the surface of the tissue

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12
Q

Anticlinal

A
  • right angles

- describes cell divisions in planes at right angles to the outer surface of a tissue

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13
Q

Auxin

A
  • Is a major plant hormone
  • It’s trafficking within the embryo controls polarity and cell fate
  • Accumulates in the embryo proper early in development
  • The growth of lateral buds immediately below the apical shoot meristem are suppressed by auxin = apical dominance
  • Auxin diffuses to inhibit the development of the lateral shoot meristem
  • small organic molecule that is an important plant hormone in almost all aspects of plant development
  • acts by regulating the expression of auxin-responsive genes by stimulating the degradation of Aux/IAA proteins and thus enabling gene expression
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14
Q

Establishment of Cell polarity

A
  • PIN1=auxin
  • 16-cell embryo: PIN1 uniformly distributed relative to the longitudinal axis
  • mid-globular stage embryo: PIN1 accumulates at basal end of specific cells
  • heart-shaped embryo: PIN1 accumulates at the apex of epidermal cells in the cotyledons; PIN1 accumulates at the base of procambial cells
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15
Q

PIN1

A
  • A specific auxin efflux carrier (asymmetrical carrying auxin from one cell to the other)
  • Loss of PIN 1 activity results in a pin-like bolt and the complete loss of lateral organs (leaves)
  • Additional efflux carriers have since been found: PIN2, 3, 4 and 7 are required for regulated growth and development
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16
Q

Hormone traffic

A
  • genetic defects in hormone traffic or perception produce plants with altered body parts
  • hormone traffic regulated by GNOM (gn)
17
Q

GNOM

A
  • Encodes and ADP ribosylation GTP exchange factor (ARF GFFs)
  • Regulates the hormone traffic of membrane vessicles
  • Mutants in GNOM show a loss of apical basal polarity
  • GNOM is required for PIN1 localization
18
Q

Embryonic shoot meristem

A

-becomes the shoot apical meristem, mainted after germination, gives rise to all stems, leaves and flowers

19
Q

Root meristem

A

gives rise to root structures

20
Q

Internode

A
  • that portion of a plant stem between two nodes
  • sites at which a leaf or leaves form
  • Plants develop in models and consist of an internode (the cells produced by the meristem between leaf initiations)
21
Q

Meristems

A
  • Meristems are undifferentiated stem cell populations that generate the stem, leaf and flower as well as root structure of the post-embryonic plant
  • the meristem regions have formed by the heart stage of embryo development
  • Most plant structures are generated by meristems with the deception of stem growth (cambium does this)
22
Q

Axillary bud

A
  • forms the lateral shoot meristem

- a bud that grows from the axil of a leaf and may develop into a branch or flower cluster.

23
Q

Lateral shoot meristem

A
  • meristem that arises from the apical shoot meristem and gives rise to lateral shoots
  • Cell-cell interactions are a major determinant of cell fate, if the shoot apex is removed, the lateral shoot meristem becomes active to create a new shoot
24
Q

Apical dominance

A
  • The growth of lateral buds immediately below the apical shoot meristem are suppressed
  • This suppression requires the hormone auxin that is produced by the shoot apex
  • Auxin diffuses to inhibit the development of the lateral shoot meristem
  • the phenomenon in plants that buds in the axils of nodes behind the tip of a plant shoot will not form side stems when the tip is intact
  • it is due to the production of the hormone auxin by the shoot tip which suppresses outgrowth of axillary buds
25
Q

Central zone

A
  • zone of the shoot apical meristem
  • Central zone is a slowly dividing stem cell population that are self-renewing (12-20 cells that persist through the entire life of the plant)
26
Q

Rib zone

A
  • zone of the shoot apical meristem
  • Rib zone gives rise to central tissues, some of these yellow cells are an organizing centre, underly the central zone and maintain a microenvironment that maintains the stem cell identity
27
Q

Peripheral zone

A
  • zone of the shoot apical meristem
  • Peripheral zone are proliferating cells that are determined to differentiate into shoots, stems, or leaves (as well as flower organ with the right signal or cue)
28
Q

Organ initiation

A

-SAM maintenance is dependent on the coordination of two antagonistic processes: organ initiation and self-renewal of stem cell population

29
Q

Self-renewal of stem cell population

A

-SAM maintenance is dependent on the coordination of two antagonistic processes: organ initiation and self-renewal of stem cell population

30
Q

Shoot meristemless (STM)

A
  • In STM mutants, the meristem is absent by the end of embryogenesis
  • Maintains stem cells population and prevents premature determination
31
Q

Wuschel (WUS)

A
  • In wus mutants, the stem cells fail to establish in the embryo
  • Maintain the pool of stem cells
32
Q

Clavata (CLV) genes

A
  • These inhibit the size of the meristem
  • Clavata mutants have enlarged meristems at the expense of organ formation
  • Required to promote organ formation/differentiation
  • CLV1: Receptor kinase protein
  • CLV2: Receptor protein
  • CLV3: Secreted peptide ligand
  • Interaction between WUS (Wuschel) and CLV genes establishes a negative feedback loop maintaining stem cells and the underlying organizing centre
33
Q

Over-expression of STM (shoot meristemless)

A
  • increases meristematic activity in Arabidopsis
  • Increasing STM (shoot meristemless)= increase in size of SAM, increased production of flowers, therefore production of fruits and seeds
34
Q

Shoot apical meristem (SAM)

A

-Most apical node
-Is central to plant development
-Contains a few hundred undifferentiated cells that are capable of cell division
-Most cell division in the plant occurs in this meristem or as cells leave the meristem
-Cell growth outside the meristem is associated with cell enlargement and growth
-The meristem is an organizing centre and is maintained by self-renewing stem cells
3 main zones: central zone, rib zone and peripheral zone
-Central zone is a slowly dividing stem cell population that are self-renewing (12-20 cells that persist through the entire life of the plant)
-Rib zone gives rise to central tissues, some of these yellow cells are an organizing centre, underly the central zone and maintain a microenvironment that maintains the stem cell identity
-Peripheral zone are proliferating cells that are determined to differentiate into shoots, stems, or leaves (as well as flower organ with the right signal or cue)
-SAM maintenance is dependent on the coordination of two antagonistic processes: organ initiation and self-renewal of stem cell population

BIOL 3542 (10 decks)

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