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Shoot meristem self-organization and identity

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 ).

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Shoot meristem self-organization and identity

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  1. Shoot meristem self-organization and identity

  2. Vegetative shoot apical meristem (SAM)

  3. Wild-type shoot apex shootmeristemless apex (from Long et al., 1996, Nature 379: 66-69)

  4. Gene expression in embryonic SAM WUSCHEL (WUS) SHOOTMERISTEMLESS (STM) (from Laux et al., 1998, Cell 95: 805-815)

  5. Wild type wuschel mutant (from Laux et al., 1998, Cell 95: 805-815)

  6. Gene expression in embryo SAM WUSCHEL (WUS) SHOOTMERISTEMLESS (STM) (from Laux et al., 1998, Cell 95: 805-815)

  7. WUS expression in adult shoot meristems (from Laux et al., 1998, Cell 95: 805-815)

  8. clavata mutants have enlarged meristems Wild type clavata3 mutant clv1 and clv3 mutants look similar (from J. C. Fletcher et al., Science 283, 1911 -1914 (1999))

  9. Expression of CLV1 in Arabidopsis inflorescence shoot meristem Clark et al., Cell 89: 575-585 (1997)

  10. CLV3 (A-D) and CLV1 (E) expression (from J. C. Fletcher et al., Science 283, 1911 -1914 (1999))

  11. CLV3 expression in a clv1 mutant meristem (from J. C. Fletcher et al., Science 283, 1911 -1914 (1999))

  12. Model for CLV3 peptide signaling

  13. Model for shoot apical meristem (SAM) maintenance 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.

  14. Similar regulation in shoot and root meristems WOX5 is similar in sequence to WUSCHEL. WOX5 is expressed in the root quiescent center. Sarkar et al. (2007) Nature 446: 811-814

  15. Similar regulation in shoot and root meristems Root cap stem cells differentiate in a wox5 mutant. Sarkar et al. (2007) Nature 446: 811-814

  16. Inflorescence meristem: Makes flowers instead of leaves and branches Stem elongates more

  17. Shoot meristem identities Sepals, petals, stamens, carpels Flower meristems Inflorescence SAM Leaves, branches (lateral meristems) Induction of flowering Vegetative SAM

  18. Shoot meristem identities Sepals, petals, stamens, carpels Flower meristems (determinate) Inflorescence SAM (indeterminate) Leaves, branches (lateral meristems) Induction of flowering Vegetative SAM (indeterminate)

  19. Vegetative shoot apical meristem (SAM)

  20. Flower meristems Shoot apical meristem (SAM)

  21. Flower meristem Flower

  22. Arabidopsis flower Stamen Gynoecium (fused carpels) Petal Sepal

  23. Shoot meristem identities Sepals, petals, stamens, carpels Flower meristems (determinate) Inflorescence SAM (indeterminate) Leaves, branches (lateral meristems) Induction of flowering Vegetative SAM (indeterminate)

  24. 1 2 3 4 4sepals 4 petals 6 stamens 2 carpels Whorls

  25. Arabidopsis mutants with altered flowers Wild type apetala1 cauliflower apetala1 agamous pistillata

  26. Shoot meristem identities Sepals, petals, stamens, carpels Flower meristems Meristem identity genes (LFY, AP1, CAL) Inflorescence SAM Leaves, branches (lateral meristems) Induction of flowering Vegetative SAM

  27. leafy mutants: partial conversion of flowers to lateral branches and leaves

  28. leafy mutant flowers have no petals or stamens Wild type leafy

  29. LEAFY is expressed throughout the flower meristem (from Weigel et al., 1992, Cell 69: 843-859)

  30. apetala1 mutant flowers lack sepals and petals and have a new flower where a petal should be Wild type apetala1

  31. Flowers are converted into leafy shoots in leafy apetala1 mutants

  32. Flower meristems behave like inflorescence meristems in the apetala1 cauliflower double mutant ap1 cal ap1 cal Fig. 20.41

  33. Why did they call this mutant cauliflower? ap1 cal

  34. Shoot meristem identities Sepals, petals, stamens, carpels Organ identity genes (AP1, AP2, PI, AP3, AG SEP1, SEP2, SEP3) Flower meristems Inflorescence SAM Leaves, branches (lateral meristems) Induction of flowering Vegetative SAM

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