THE PLANT CELL, Vol 1, Issue 8 775-782, Copyright © 1989 by American Society of Plant Biologists
Rice Phytochrome Is Biologically Active in Transgenic Tobacco
S. A. Kay, A. Nagatani, B. Keith, M. Deak, M. Furuya and N. H. Chua
The Laboratory of Plant Molecular Biology, The Rockefeller University, New York, New York 10021
To investigate the mechanisms of phytochrome action in vivo, we have
overexpressed rice phytochrome in transgenic tobacco plants. A full-length
rice phytochrome cDNA was fused to the cauliflower mosaic virus 35S
promoter and transferred to tobacco. The progeny of some of the transgenic
plants contain large amounts of rice phytochrome mRNA in green leaves.
Extracts prepared from overexpressing plants contain twofold to fivefold
more spectrophotometrically detectable phytochrome than extracts from
control plants. Species-specific, anti-phytochrome monoclonal antibodies
were used in immunoblots to discriminate between rice and tobacco
phytochrome apoproteins in fractions eluted from a DEAE-Sepharose column.
Red minus far-red difference spectra of the partially purified rice
phytochrome from the transgenic plants indicate that the rice phytochrome
assembles with chromophore and is photoreversible. Analysis of the
circadian pattern of Cab mRNA levels in transgenic plants versus controls
demonstrates that the overproduction of rice phytochrome extends the
duration of the free-running rhythm of Cab gene expression. The rice
phytochrome is, therefore, biologically active in the transgenic tobacco
plant, which establishes a system for in vivo functional analysis of
phytochrome.