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Two Native Pools of Phytochrome A in Monocots: Evidence from Fluorescence Investigations of Phytochrome Mutants of Rice
Author(s) -
Sineshchekov Vitaly,
Loskovich Alexander,
Inagaki Noritoshi,
Takano Makoto
Publication year - 2006
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1562/2005-12-10-ra-749
Subject(s) - phytochrome , phytochrome a , coleoptile , mutant , protochlorophyllide , biology , etiolation , biophysics , oryza sativa , biochemistry , chemistry , botany , arabidopsis thaliana , gene , biosynthesis , enzyme , red light
Fluorescence investigations of phytochrome (phy) in rice ( Oryza sativa L. cv. Nipponbare) mutants deficient in phyA, phyB and phyA plus phyB were performed. Total content of the pigment (P tot ) and its spectroscopic and photochemical characteristics were determined in different parts of the dark‐grown and far‐red light (FR)‐grown coleoptiles. Spectroscopically, phyA in the phyB mutant was identical to phyA in the wild‐type (WT) and the extent of the conversion from Pr to lumi‐R at 85 K was the same for phyA in both lines and varied similarly, depending on the part of the coleoptile used. The latter finding proved that phyA in rice is heterogeneous and comprises two phyA populations, phyA′ and phyA″. Functional properties of phyA were also determined. In the dark the phyB mutant had a higher content of phyA, inactive protochlorophyllide (Pchlide 633 ) and active protochlorophyllide (Pchlide 655 ) than WT and its coleoptile was longer, indicating that phyB may affect the development of WT seedlings in the dark. Constant FR drastically reduced the content of phyA, Pchlide 633 and Pchlide 655 and brought about coleoptile shortening and appearance of the first leaf, whereas pulsed FR of equal fluence was less effective. This suggested that the reactions were primarily of the high irradiance responses type, which are likely to be mediated by phyA′. The effects on protochlorophyllide biosynthesis and growth responses type were more pronounced in the phyB mutant than in the WT seedlings, which can be connected with the higher phyA′ content in the phyB mutant and/or phyB interference with its action in WT seedlings. In the phyA mutant induction of Pchlide 633 and Pchlide 655 biosynthesis was observed under constant FR, indicating that phyC may be responsible for this effect.