The cucumber long hypocotyl mutant lacks a light-stable PHYB-like phytochrome.
A novel cDNA sequence homologous to a phytochrome B (phyB) gene that was isolated in a library from tobacco tissue has been used in an Escherichia coli expression system to raise anti-phytochrome B (anti-PHYB) polypeptide-specific monoclonal antibodies. The specificity of these antibodies has been tested by cross-reactivity against purified pea light-labile type 1 and light-stable type 2 phytochromes, with some antibodies reacting with the type 2 and none with the type 1 phytochromes. One such antibody, monoclonal mAT1, has been employed to analyze the phytochrome molecular species present in a photomorphogenic long hypocotyl (lh) mutant of cucumber. The results indicated that the mutant contains wild-type levels of the light-labile type 1 phytochrome polypeptide (PHYA), which has an apparent molecular mass of approximately 120 kD, but shows less than 1% (detection limit) of a light-stable polypeptide recognized by mAT1 in wild-type seedlings. This protein, not detectable in the lh mutant, has the properties of light-stable type 2 phytochrome, has an apparent molecular mass of 116 to 117 kD, and remains at constant levels under continuous low-fluence-rate red light. Therefore, we conclude that the lh mutant lacks at least one type 2 phytochrome-like polypeptide, most probably a phyB gene product. The correlation between the lack of this protein and the deficiency or absence of physiological responses to a light-stable phytochrome species in this mutant helps to identify the physiological roles played by the products of different subfamilies within the phytochrome gene family.
López-Juez
E
E
Laboratory of Plant Biological Regulation, Frontier Research Program, RIKEN Institute, Saitama, Japan.
Nagatani
A
A
Tomizawa
K
K
Deak
M
M
Kern
R
R
Kendrick
R E
RE
Furuya
M
M
D000911:Antibodies, Monoclonal / Q000276:immunology; D003001:Cloning, Molecular; D003429:Cross Reactions; D004926:Escherichia coli; D008027:Light; D009154:Mutation; D010786:Photoreceptor Cells; D010834:Phytochrome / Q000235:genetics* / Q000276:immunology; D051939:Phytochrome B; D010944:Plants / Q000235:genetics* / Q000528:radiation effects; D014157:Transcription Factors
D000911:Antibodies, Monoclonal; D014157:Transcription Factors; D010834:Phytochrome; D051939:Phytochrome B