Variation in dynamics of phytochrome A inArabidopsisecotypes and mutants

Phytochromes are photoreceptors in plants which can exist in two different conformations: the red light‐absorbing form (Pr) and the far‐red light‐absorbing form (Pfr), depending on the light quality. The Pfrform is the physiologically active conformation. To attenuate the Pfrsignal for phytochrome A (phyA), at least two different mechanisms exist: destruction of the molecule and dark reversion. Destruction is an active process leading to the degradation of Pfr. Dark reversion is the light‐independent conversion of physiologically active Pfrinto inactive Pr. Here, we show that dark reversion is not only an intrinsic property of the phytochrome molecule but is modulated by cellular components. Furthermore, we demonstrate that dark reversion of phyA may be observed inArabidopsisecotype RLD but not in otherArabidopsisecotypes. For the first time, we have identified mutants with altered dark reversion and destruction in a set of previously isolated loss of function PHYA alleles (Xuet al. Plant Cell1995, 7, 1433–1443). Therefore, the dynamics of the phytochrome molecule itself need to be considered during the characterization of signal transduction mutants.