(A) Light-grown corn (B) Dark-grown corn (c) Light-grown bean (D) Dark-grown bean Figure g-1
Figure 9-1
Dark Red Far-red Figure 9-2 数 FIGURE 17.2 Lettuce seed germination is a typical photore- versible response controlled by phytochrome. Red light promotes lettuce seed germination, but this effect is reversed by far-red light. Imbibed(water-moistened)seeds were given alternating treatments of red followed by far red light. The effect of the light treatment depended on the Red Far-red Red Red Far-red Red Far-red last treatment given. (Photos O M B. Wilkins
Figure 9-2
First node 12 长10 FIGURE 17.6 Phytochrome is 20 most heavily concentrated in Root the regions where dramatic developmental changes are 20 curring: the apical meristem of the epicotyl and root Shown 10 here is the distribution of ph chrome in an etiolated pea seedling, as measured spec Concentration of phytochrome Kendrick and Frankland 1983) Figure 9-3
Figure 9-3
Chromophore: phytochromobilin P His ser B N 1 ys Leu Thioether Cis isomer GIn linkage Red light converts cis to trans Pro R R 15 se 1 Trans isomer His Leu GIn igure 9-5 FIGURE 17. 4 Structure of the Pr and pfr forms of the chro mophore (phytochromobilin) and the peptide region bound to the chromophore through a thioether linkage. The chro- mophore undergoes a cis-trans isomerization at carbon 15 in response to red and far-red light. (After Andel et al. 1997.)
Figure 9-5
Chromophore-binding domains A A B IIB FIGURE 17.5 Structure of the phytochrome dimer. The monomers are labeled I and Il. Each monomer consists of a chromophore-binding domain(A)and a smaller nonchro mophore domain(b). The molecule as a whole has an elli soidal rather than globular shape. (After Tokutomi et al 1989) Figure g-5-1
Figure 9-5-1
(A) Phytochrome chromophore Cys) HO,C CO2H 3C HC ANH B C D O N H Figure 9-5-2 (B) Phytochrome protein Ser- Chromophore TKD2 TKD1 NoI B■ C
Figure 9-5-2
(C) Absorption spectra of PR and PFR 0.8 O.4 Figure 18.23 Structure and func- tion of phytochromes. (A) The phytochrome 300 40O SOO 600 70O 8O0 chromophore is a tetra- pyrrole that binds to the Wavelength (nm) phytochrome protein (B) The C termini of plant phytochromes may contain two distinct (D) Phytochrome activities transmitter kinase do- mains, TKD2 and TKDI 660nm lopmental (C) Absorption spectra R f Pr and PFR show 730nm responses peaks for red (66o nm) and far-red (730 nm) light, respectively. (D)Phytochromes can 660nm exist as either of two interconvertible forms 730nm germination Isolated phytochromes in a concentrated solu- tion can undergo re- 660nm versible changes in absorbance induced by 730nm illumination with red or far-red light. These light-induced structural Greening of changes are coincident with physiological and seedling developmental changes Figure 9-5-3 induced by red light or blocked by far-red light
Figure 9-5-3
NUCLEUS PLASTID -PHYA mRNA Phytochromobilin Phytochrome apoprotein Figure 9-6 Phytochrome Red holoprotein Pr Far-red Pfr CYTOSOL Figure 17.6 Phytochromobilin is synthesized in plastids and released into the cytosol, where it assembles with the phy tochrome apoprotein (After Kendrick et al. 1997.)
Figure 9-6
(A) Bacterial phytochrome Red light (Chromophore) ensor protein CInput Transmitte His ID Response requlator protein (Chromophore) 式ATP I Asp ReceiveroutputDD CI Input Transmitter His I 1. After receiving a signal from th Asp Receiver Output sensor protein autophosphorylates a histidine 2. The phosphorylated sensor protein phosphorylates the response regulator output protein at an aspartate 3. The phosphorylated espon (B) Plant phytochrome stimulates the response Red light (Chromophore HN I Kinase domain Phytochrome 1. Phytochrome is aTPA on serine ()(Chromophore) Kinase donain COOH FIGURE 17.21 Phytochrome is an autophospho- rylating protein kinase (A) Bacterial ph tochrome is an exanple of a two-component signaling system, in which phytochrome func ions as a sensor protein that phosphorylates response regulator (see Chapter 14 on the weh 2. Phytochrome may phosphorylate other igure 9-11 site).(B) Plant phytochrome is an autophospho- rylating serine/threonine kinase that may phos-
Figure 9-11
(9 Dark Light (2 CYTOPLASM PsK1 Light∈cop1)Dark For red light PsK1 12 05、。ak - ATP Pf CPtA HYS degradation Light-requlated 9ene。 xpression COP/DET/FUS) cGMP=----- proteasome protein c一cM NUCLEUS Light pfrB>① CPfr(P Light (IF 3 (NDPK2 Rod Far red lght light (NDPK2 (1 Rod light converts PrA and PrB to their Pfr forms () The Pfr forms of phyA and phyB phytochrome can autophosphorylate. Activated PfrA phosphorylates phytochrome kinase substrate 1(PKs)) O Activated PtrA and ptre may interact with G-proteins. G cGMP, calmodulin(CAM), and calcium (ca") may activate transcription factors (x and n) Activated PfrA and PfrB enter the nucleus. interacting factor 3(PIF3). transcription directly or through interaction with phytochrome (8 Nucleoside diphosphate kinase 2(NDPK2) is activated by PfrB. In the dark, COPl enters the nucleus and suppresses light-regulated genes. Figure 9-12 Go In the dark, CoP1. an E3 ligase, ubiquitinates HYs (D In the dark, HY5 is degraded with the assistance of the COP/DET/FUS proteasome complex. (2) In the light, coPt interacts directly with SPAl and is exported to the cytoplasm FIGURE 17.22 Summary diagram of the known factors involved in phytochrome- (A sth gene will be uncovered as more signaling intermediates are identifloei"pe
Figure 9-12
