Phytochrome from Protonemal Tißue of the Moß Ceratodon purpureus

Abstract

Extracts of protonemal filaments of the moss Ceratodon purpureus were analysed for phytochrome by photoreversibility measurements and immunoblotting. Phytochrome content in vivo is light dependent ; following transfer from white light to darkness, phytochrome accumulated over a 7-day period, whereas upon transfer from darkness to light, phytochrome content decreased rather slowly. In vitro, part of the Ceratodon phytochrome pool showed a rapid (< 10 min) dark reversion from Pfr to Pr. A Pr minus Pfr difference spectrum of partially-purified phytochrome showed an absorbance maximum at 660 nm and a minimum at 722 nm. A polyclonal antibody, APC1, was raised against the 5' coding region of the Ceratodon phytochrome gene PHYCER 1 overexpressed in E. coli. A 132 kD phytochrome band was stained on immunoblots ; the same polypeptide was stained with the «universal» anti-phytochrome antibody, Z-3B1. This polypeptide probably represents the dominant photoreversible phytochrome in Ceratodon. Discrepancies between these data and parameters expected from PHYCER1 based on the gene sequence imply that the predominant photoreversible phytochrome is, however, not PHYCER1. A 5' fragment of a novel gene, PHYCER2, likely to encode the predominant phytochrome, was cloned and sequenced.