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Etiolated plant

Etiolated plant. Light grown. Effective Light Qualities = Red & Blue Spectral Region s. Blue = Cryptochrome - Phototropin - Zeaxanthin Red = Phytochrome. Red Light (650-680 nm). Far-Red Light (710-740). Phytochrome = Blue Protein- Pigment (125 kDa) Pr = Red Light-Absorbing Form

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Etiolated plant

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  1. Etiolated plant

  2. Light grown

  3. Effective Light Qualities= Red& BlueSpectral Regions Blue= Cryptochrome - Phototropin - Zeaxanthin Red = Phytochrome

  4. Red Light (650-680 nm)

  5. Far-Red Light (710-740)

  6. Phytochrome = Blue Protein-Pigment(125 kDa) Pr = Red Light-Absorbing Form Pfr = Far-Red Light-Absorbing Form Phytochrome = PhotoReversible Blue Form (Pr) absorbs Red Light Blue Green Form (Pfr) absorbs Far Red Light  Blue Form (Pr) absorbs Red Light Blue Green Form (Pfr) absorbs Far Red Light  P660_____ P695_____P710_____P730 P730________P650______P660

  7. There are two basic types of Phytochrome called Type I and Type II. • Type Ipredominates in Etiolated tissues. • Type I Phytochrome is the gene product of PHYA. • Type I is unstable in the light. • Type II phytochrome is produced by PHYB-E. • Type II is stable in the light. • Type I phytochrome responses are typical for Etiolated plants while Type II phytochrome is responsible for most other responses

  8. Phytochrome A is light-labile • Phytochrome A accumulates in etiolated seedlings, but is depleted • when plants are grown in the light • Phytochromes B, C, D and E are light-stable • The levels of phytochromes B, C, D and E are more-or-less constant • throughout plant development

  9. Pr Pfr Far-Red Light P660/P730 •red/far red absorbance •peaks in red and blue •studied by difference spectra •reach photoequilibrium because of overlap of spectrum •85% red/15% far red

  10. Phytochrome structure protein •chromophore: open chain tetrapyrrole •dimer

  11. Photo-transformations

  12. Protein: 125 kD (~1200 aa’s) with 2 domains Protein kinase: catalyzes the rxn Protein-OH +ATP 􀃆 Protein-OPO3

  13. Distribution Phtyochrome is a cytosolic protein

  14. A partner protein is identified for PhyB called PIF3 (PhyB-Interacting Factor #3). Red light causes PhyB to move into nucleus and interact with PIF3, a transcription factor that activates the genes encoding other transcription factors for activation of photosynthetic genes.

  15. Light Pr to Pfr pfr

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