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Developmental control and biotechnology of floral pigmentation

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  1. Introduction.
  2. The biosynthesis of plant pigments.
    1. Flavonoid and betalain pigments.
    2. The requirement for appropriate enzyme complexes to be formed.
  3. The biosynthesis of flavonoids.
    1. Formation of flavonoid pathway precursors.
    2. Formation of chalcones and aurones.
    3. Formation of flavones and dihydroflavonols.
    4. Formation of flavonols and leucoanthocyanidins.
    5. Formation of anthocyanins.
    6. B-ring hydroxylation.
    7. Vacuolar import.
    8. The biosynthesis of carotenoids.
    9. Formation of IPP.
    10. Formation of phytoene.
    11. Formation of carotene pigments.
    12. Formation of xanthophyll pigments.
    13. Pigments derived from carotenoid catabolism.
  4. The biosynthesis of betalains.
  5. Conclusion.

For many angiosperms, pigment formation is a key part of flower development. At least 200 plant genera contain species that show color change during flower development. Thus, variation in flower color associated with a change in nectar and pollen availability may be a common occurrence. The production of pigments in complex patterns that are coincident with fertility and localized to particular cell types within the flower requires the coordinated induction of the genes for the pigment biosynthetic enzymes. In addition to the developmental signals, the pigment biosynthetic genes may respond to environmental factors such as the light quality and quantity.

[...] Floral pigmentation is under strict developmental control and is commonly linked to fertility status. The developmental signalling involved can be complex, as more than one pigment pathway, and other pathways regulating other components that affect color like vacuolar pH, may be coordinately controlled. SUMMARY This text reviews the knowledge on the regulation of pigment production during flower development, with an emphasis on the transcriptional regulation of the biosynthetic genes. It also provides a brief overview of the major flower pigment biosynthetic pathways. [...]

[...] Furthermore, esterification is a common characteristic of floral carotenoids, and may aid in the accumulation of the high levels of pigment found in chromoplasts. Pigments derived from carotenoid catabolism The vividly colored apocarotenoids are formed by cleavage of the normal C40 carotenoid structure. They occur in various plant tissues including roots, stems and flowers. Saffron, an expensive spice made from the dried red styles of saffron flowers, derives its distinctive color from C20 apocarotenoid crocetin glycosides. These are probably formed by cleavage of zeaxanthin by zeaxanthin 8(7', 8')-cleavage dioxygenase, a plastid- localized enzyme that removes the cyclic rings from both ends. [...]

[...] The following sections briefly describe the formation of carotenoid precursors, the branches of the carotenoid pathway common to all plants and the biosynthesis of carotenoid cleavage products, with emphasis on aspects pertaining to chromoplasts and floral pigmentation. Formation of IPP The plastidic 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway is the main source of IPP used in carotenoid synthesis. However, the cytosolic mevalonic acid pathway also produces IPP, and in some instances this is linked with carotenoid production. In the MEP pathway, 1-deoxy-D-xylulose phosphate which is derived from the condensation of pyruvate and glyceraldehyde-3-phosphate, is converted to MEP through the action of deoxy-D-xylulose 5-phosphate reductoisomerase (DXR). [...]

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