Journal Article

Phytochrome Control of Phototropism and Chlorophyll Accumulation in the Apical Cells of Protonemal Filaments of Wildtype and an Aphototropic Mutant of the Moss <i>Ceratodon purpureus</i>

Tilman Lamparter, Heike Esch, David Cove and Elmar Hartmann

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 38, issue 1, pages 51-58
Published in print January 1997 | ISSN: 0032-0781
Published online January 1997 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/oxfordjournals.pcp.a029084
Phytochrome Control of Phototropism and Chlorophyll Accumulation in the Apical Cells of Protonemal Filaments of Wildtype and an Aphototropic Mutant of the Moss Ceratodon purpureus

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The aphototropic mutant line ptrll6 of the moss Ceratodon purpureus shows characteristics of a deficiency in the phytochrome chromophore. Photoreversibility measurements indicate an approximately 20 time lower concentration of spectrally active phytochrome compared to wild-type, whereas normal phytochrome apoprotein levels are found on immunoblots. Feeding with the tetrapyrroles biliverdin, the proposed precursor of the phytochrome chromophore, or phycocyanobilin, which may replace the phytochrome chromophore, resulted in the rescue of ptrll6 phototropism.

The ptrll6 mutant and the phenotypically-related mutant ptrl contain lower chlorophyll levels than the wild-type. Chlorophyll content of wildtype and mutant tissue grown under different light conditions was estimated using conventional spectrophotometry of extracts and fluorimetrically, on single apical cells. Dark-grown tissue contained about 100 times less chlorophyll than tissue grown under standard white light conditions. Red light given for 24 h to dark adapted filaments induced an increase in the chlorophyll content in the wildtype, but not in ptrl16. Blue light induced an increase in chlorophyll both in wildtype and in ptrl16. The red light effect on the wildtype was partially reversible with far-red. If ptrl16 was grown on phycocyanobilin, an increase in chlorophyll was also found when cells were irradiated with red light.

The results indicate that phytochrome as well as a blue light photoreceptor regulate chlorophyll accumulation in C. purpureus protonemata. It can be assumed that in ptrll6, the synthesis of the phytochrome chromophore is blocked specifically beyond the synthesis common to chlorophyll and the phytochrome chromophore and affects an enzymatic step between protoporphyrin and biliverdin.

Keywords: Blue light photoreceptor; Ceratodon purpureus; Phototropism; Phycocyanobilin; Phytochrome (chromophore); Regulation of chlorophyll synthesis

Journal Article.  0 words. 

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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