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Floral Organ Development in Arabidopsis: Morphological Series and Gene Mutations

Explore the morphological series and gene mutations in Arabidopsis flower development, including the ABC model and the role of SEPALLATA genes. Discover how gene changes can impact flower phenotype.

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Floral Organ Development in Arabidopsis: Morphological Series and Gene Mutations

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  1. Morphological series Stamen series from leaf-like to a slender filament.

  2. Carpels from leaf-like (conduplicate carpel) to carpels with a highly defined stigma, style and ovary.

  3. Basic “ABC Model of Floral Organ Development

  4. Normal wild-type Arabidopsis thaliana (Brassicaceae)

  5. Arabidopsis showing 4 floral organs Carpels-C StamensB&C Petals-A&B Sepals-A

  6. apetala 2 mutant No A(Ca -St-St - Ca)

  7. St St Ca Ca Apetala mutant No A (Ca -St-St - Ca) Wild Type Flower

  8. apetala or pistillata mutant, No B (Se-Se-Ca-Ca)

  9. Side View Top View C- Class Mutants AGAMOUS mutant No Gametes (Se-Pe-Pe-Se-Pe-Pe)

  10. The name of a gene describes the flower when that gene is not functional. A-Class Mutant No APETALA 1 or APETALA2 No Petals (only carpels and stamens) B-Class Mutant APETALA 3 or PISTILLATA No petals or a lot of Pistils

  11. Side View Top View C- Class Mutants AGAMOUS mutant No Gametes (Se-Pe-Pe-Se-Pe-Pe)

  12. The SEPALLATA genes alone cannot direct flower development. If you turn on the SEPALLATA genes in vegetative plants you get petal-like structures where leaves should be, but none of the other flower parts were present. If you turn on the ABC genes without SEPALLATA genes, you also do not get a flower. So BOTH sets of genes are necessary for normal flower development.

  13. Flower structure and the “quartet model” of floral organ specification in Arabidopsis (From Nature409, 469 - 471 (2001)

  14. Ancient Gene ABC plus model Note addition of SEPALLATA genes and others (green, blue and black). Even though it is more complex-- a gene change here or there can have a profound effect on flower phenotype.

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