Shoot meristem self-organization and identity. Vegetative shoot apical meristem (SAM)
-
date post
23-Jan-2016 -
Category
Documents
-
view
222 -
download
1
Transcript of Shoot meristem self-organization and identity. Vegetative shoot apical meristem (SAM)
Shoot meristem self-organization and identity
Vegetative shoot apical meristem (SAM)
(from Long et al., 1996, Nature 379: 66-69)
Wild-type shoot apex shootmeristemless apex
Gene expression in embryonic SAM
WUSCHEL (WUS) SHOOTMERISTEMLESS (STM)
(from Laux et al., 1998, Cell 95: 805-815)
wuschel mutant
(from Laux et al., 1998, Cell 95: 805-815)
Wild type
Gene expression in embryo SAM
WUSCHEL (WUS) SHOOTMERISTEMLESS (STM)
(from Laux et al., 1998, Cell 95: 805-815)
WUS expression in adult shoot meristems
(from Laux et al., 1998, Cell 95: 805-815)
(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
Expression of CLV1 in Arabidopsis inflorescence shoot meristem
Clark et al., Cell 89: 575-585 (1997)
CLV3 (A-D) and CLV1 (E) expression
(from J. C. Fletcher et al., Science 283, 1911 -1914 (1999))
CLV3 expression in a clv1 mutant meristem
(from J. C. Fletcher et al., Science 283, 1911 -1914 (1999))
Model for CLV3 peptide signaling
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
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
Sarkar et al. (2007) Nature 446: 811-814
Root cap stem cells differentiate in a wox5 mutant.
Similar regulation in shoot and root meristems
Inflorescence meristem:
Makes flowers instead of leaves and branches
Stem elongates more
Vegetative SAM
Inflorescence SAM
Flower meristems
Leaves, branches (lateral meristems)
Sepals, petals, stamens, carpels
Induction of flowering
Shoot meristem identities
Vegetative SAM (indeterminate)
Inflorescence SAM (indeterminate)
Flower meristems (determinate)
Leaves, branches (lateral meristems)
Sepals, petals, stamens, carpels
Induction of flowering
Shoot meristem identities
Vegetative shoot apical meristem (SAM)
Flower meristems
Shoot apical meristem (SAM)
Flower meristem Flower
Arabidopsis flower
Sepal
Stamen
Gynoecium(fused carpels)Petal
Vegetative SAM (indeterminate)
Inflorescence SAM (indeterminate)
Flower meristems (determinate)
Leaves, branches (lateral meristems)
Sepals, petals, stamens, carpels
Induction of flowering
Shoot meristem identities
1 2 3 4
4 sepals
4 petals
6 stamens
2 carpels
Whorls
Arabidopsis mutants with altered flowers
apetala1apetala1cauliflower
pistillata
Wild type
agamous
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
leafy mutants:partial conversion of flowers to lateral branches and leaves
leafy mutant flowers have no petals or stamens
leafy
Wild type
LEAFY is expressed throughout the flower meristem
(from Weigel et al., 1992, Cell 69: 843-859)
apetala1 mutant flowers lack sepals and petals and have a new flower where a petal should be
Wild type apetala1
Flowers are converted intoleafy shoots in leafy apetala1 mutants
Flower meristems behave like inflorescence meristems in the apetala1 cauliflower double
mutant
ap1 cal
ap1 cal
Fig. 20.41
ap1 cal
Why did they call this mutant cauliflower?
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