Dynamic properties of endogenous phytochrome A in Arabidopsis seedlings.
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.
Hennig
L
L
Institut für Biologie II, Universität Freiburg, Schänzlestrasse 1, 79104 Freiburg, Germany.
Büche
C
C
Eichenberg
K
K
Schäfer
E
E
D017360:Arabidopsis / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D029681:Arabidopsis Proteins; D003624:Darkness; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects*; D007700:Kinetics; D008027:Light; D010834:Phytochrome / Q000235:genetics* / Q000378:metabolism*; D051942:Phytochrome A; D012333:RNA, Messenger / Q000235:genetics
D029681:Arabidopsis Proteins; C497973:PHYA protein, Arabidopsis; D051942:Phytochrome A; D012333:RNA, Messenger; D010834:Phytochrome