Dynamic properties of endogenous phytochrome A in Arabidopsis seedlings

• Published in: Plant physiology (Bethesda) 1999-10, Vol.121 (2), p.571-577
• Main Authors: Hennig, L, Buche, C, Eichenberg, K, Schafer, E
• Format: Article
• Language: English
• Subjects: acclimation; Arabidopsis; Arabidopsis - genetics; Arabidopsis - physiology; Arabidopsis - radiation effects; Arabidopsis Proteins; Arabidopsis thaliana; Biological and medical sciences; Cell Biology and Signal Transduction; chemical constituents of plants; Chromium; dark; Darkness; far-red light; Fundamental and applied biological sciences. Psychology; Gene expression regulation; Gene Expression Regulation, Plant - radiation effects; Half lives; Irradiation; Kinetics; Light; Light quality; lighting; Messenger RNA; Metabolism; Oats; phytochrome; Phytochrome - genetics; Phytochrome - metabolism; Phytochrome A; Plant physiology and development; quantitative analysis; red light; RNA; RNA, Messenger - genetics; Seedlings; Spectroscopy; Storage and secretion, pigments, phytochrome; temporal variation; wavelengths
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.121.2.571

The dynamic behavior of phytochrome A (phyA) in seedlings of the model plant Arabidopsis was examined by in vivo spectroscopy and by western and northern blotting. Rapid accumulation of phyA was observed, reaching a steady state after 3 d. Both red and far-red light initiated a rapid destruction of the far-red-light-absorbing form of phytochrome (Pfr); the apparent half-life was only 4-fold longer in far-red than in red light. Furthermore, the Pfr-induced destruction of the red-light-absorbing form of phytochrome (Pr) of phyA occurred in darkness with a rate identical to that of Pfr destruction. A 2-fold decrease in mRNA abundance was observed after irradiation, irrespective of the applied light quality. However, reaccumulation occurred rapidly after far-red but slowly after red irradiation, indicating different modes of regulation of phytochrome expression after light-dark transitions depending on the light quality of the preceding irradiation. The wavelength dependency of the destruction rates was distinct from that of mustard, a close relative of Arabidopsis, and was explained on the basis of Pfr-induced Pr destruction and a simple kinetic two-step model. No dark reversion was detectable in the destruction kinetics after a red pulse. From these data we conclude that Arabidopsis phyA differs significantly in several aspects from other dicot phytochromes.