Particle-bound phytochrome: Differential pigment release by surfactants, ribonuclease and phospholipase C

Molecular Properties of Phytochrome

“…It does not occur in most plant extracts tested. As discussed more fully by Quail and Gressel (1976), this association is thus almost certainly an artifact and cannot be implicated in the molecular mode of action of phytochrome.…”

“…First, a small proportion of the total phytochrome pool is always associated with particulate material (Rubinstein er a/., 1969;Evans and Smith, 1976;Furuya and Manabe, 1976). Second, some phytochrome associates with particulate material and thus becomes pelletable only following photoconversion to the active Pi., form (Quail et al, 1973;Furuya and Manabe, 1976;Quail and Gressel, 1976).…”

“…Quail (1975b, c) has further demonstrated that phytochrome cosediments in sucrose gradients under a wide variety of conditions et al, 1973) with 31 S ribonucleoprotein material. The ribonucleoprotein presumably is derived from degraded ribosomal material (Quail and Gressel, 1976). As is the case for the divalent cation requirement, low pH is necessary for induction of pelletability of the 31 S particles and not for association between the particles and phytochrome (Quail, 1975~).…”

“…Low ionic strength, by contrast, is required for maintenance of the association since the 31 S particles are readily sedimented in the presence of divalent cation at ionic strengths which release phytochrome to the supernatant (Quail, 1975b). For these and other reasons discussed more fully elsewhere (Quail, 1975a;Quail and Gressel, 1976) it is almost certain that this in uitro-induced association represents an electrostatic interaction between phytochrome and ribonucleoprotein which, although it may be specific for P,, as opposed to P,, is not specific for phytochrome. The above discussion deals with unambiguous experiments which utilized in uitro irradiations.…”

“…The overriding problem which has arisen with respect to investigations of phytochrome pelletability is the realization that more than one phenomenon is involved. Because both in vitro-and in vivo-induced pelletability are observed with Cucurbita Pratt and Marme, 1976), most experiments which utilize an in vivo red irradiation result in an unknown contribution of each of the two phenomena to observed results (Quail et a/., 1973(Quail et a/., , 1976Boisard et al, 1974;Marmt, 1974;Marme et al, 1974;Quail, 1975b,c;Schafer, 1975b;Gressel and Quail, 1976;Quail and Gressel, 1976).…”