shoot meristem self-organization and identity
DESCRIPTION
Shoot meristem self-organization and identity. Vegetative shoot apical meristem (SAM). Wild-type shoot apex shootmeristemless apex. (from Long et al., 1996, Nature 379: 66-69). Gene expression in embryonic SAM. WUSCHEL ( WUS ) SHOOTMERISTEMLESS ( STM ). - PowerPoint PPT PresentationTRANSCRIPT
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Shoot meristem self-organization and identity
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Vegetative shoot apical meristem (SAM)
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(from Long et al., 1996, Nature 379: 66-69)
Wild-type shoot apex shootmeristemless apex
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Gene expression in embryonic SAM
WUSCHEL (WUS) SHOOTMERISTEMLESS (STM)
(from Laux et al., 1998, Cell 95: 805-815)
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wuschel mutant
(from Laux et al., 1998, Cell 95: 805-815)
Wild type
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Gene expression in embryo SAM
WUSCHEL (WUS) SHOOTMERISTEMLESS (STM)
(from Laux et al., 1998, Cell 95: 805-815)
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WUS expression in adult shoot meristems
(from Laux et al., 1998, Cell 95: 805-815)
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(from J. C. Fletcher et al., Science 283, 1911 -1914 (1999))
Wild type clavata3 mutant
clv1 and clv3 mutants look similar
clavata mutants have enlarged meristems
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Expression of CLV1 in Arabidopsis inflorescence shoot meristem
Clark et al., Cell 89: 575-585 (1997)
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CLV3 (A-D) and CLV1 (E) expression
(from J. C. Fletcher et al., Science 283, 1911 -1914 (1999))
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CLV3 expression in a clv1 mutant meristem
(from J. C. Fletcher et al., Science 283, 1911 -1914 (1999))
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Model for CLV3 peptide signaling
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Support for model:
In clv mutant, WUS expression domain expands.
clv wus double mutants resemble wus single mutants.
If you overexpress WUS, CLV genes are activated and new meristems form.
Model for shoot apical meristem (SAM) maintenance
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Sarkar et al. (2007) Nature 446: 811-814
WOX5 is similar in sequence to WUSCHEL.WOX5 is expressed in the root quiescent center.
Similar regulation in shoot and root meristems
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Sarkar et al. (2007) Nature 446: 811-814
Root cap stem cells differentiate in a wox5 mutant.
Similar regulation in shoot and root meristems
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Inflorescence meristem:
Makes flowers instead of leaves and branches
Stem elongates more
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Vegetative SAM
Inflorescence SAM
Flower meristems
Leaves, branches (lateral meristems)
Sepals, petals, stamens, carpels
Induction of flowering
Shoot meristem identities
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Vegetative SAM (indeterminate)
Inflorescence SAM (indeterminate)
Flower meristems (determinate)
Leaves, branches (lateral meristems)
Sepals, petals, stamens, carpels
Induction of flowering
Shoot meristem identities
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Vegetative shoot apical meristem (SAM)
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Flower meristems
Shoot apical meristem (SAM)
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Flower meristem Flower
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Arabidopsis flower
Sepal
Stamen
Gynoecium(fused carpels)Petal
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Vegetative SAM (indeterminate)
Inflorescence SAM (indeterminate)
Flower meristems (determinate)
Leaves, branches (lateral meristems)
Sepals, petals, stamens, carpels
Induction of flowering
Shoot meristem identities
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1 2 3 4
4 sepals
4 petals
6 stamens
2 carpels
Whorls
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Arabidopsis mutants with altered flowers
apetala1apetala1cauliflower
pistillata
Wild type
agamous
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Vegetative SAM
Inflorescence SAM
Flower meristems Meristem identity genes (LFY, AP1, CAL)
Leaves, branches (lateral meristems)
Sepals, petals, stamens, carpels
Induction of flowering
Shoot meristem identities
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leafy mutants:partial conversion of flowers to lateral branches and leaves
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leafy mutant flowers have no petals or stamens
leafy
Wild type
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LEAFY is expressed throughout the flower meristem
(from Weigel et al., 1992, Cell 69: 843-859)
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apetala1 mutant flowers lack sepals and petals and have a new flower where a petal should be
Wild type apetala1
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Flowers are converted intoleafy shoots in leafy apetala1 mutants
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Flower meristems behave like inflorescence meristems in the apetala1 cauliflower double
mutant
ap1 cal
ap1 cal
Fig. 20.41
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ap1 cal
Why did they call this mutant cauliflower?
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Vegetative SAM
Inflorescence SAM
Flower meristems
Leaves, branches (lateral meristems)
Sepals, petals, stamens, carpels Organ identity genes (AP1, AP2, PI, AP3, AG SEP1, SEP2, SEP3)
Induction of flowering
Shoot meristem identities