Arabidopsis HY8 locus encodes phytochrome A.
hy8 long hypocotyl mutants of Arabidopsis defective in responsiveness to prolonged far-red light (the so-called "far-red high-irradiance response") are selectively deficient in functional phytochrome A. To define the molecular lesion in these mutants, we sequenced the phytochrome A gene (phyA) in lines carrying one or other of two classes of hy8 alleles. The hy8-1 and hy8-2 mutants that express no detectable phytochrome A each have a single nucleotide change that inserts a translational stop codon in the protein coding sequence. These results establish that phyA resides at the HY8 locus. The hy8-3 mutant that expresses wild-type levels of photochemically active phytochrome A has a glycine-to-glutamate missense mutation at residue 727 in the C-terminal domain of the phyA sequence. Quantitative fluence rate response analysis showed that the mutant phytochrome A molecule produced by hy8-3 exhibited no detectable regulatory activity above that of the phyA-protein-deficient hy8-2 mutant. This result indicates that glycine-727, which is invariant in all sequenced phytochromes, has a function important to the regulatory activity of phytochrome A but not to photoperception.
Dehesh
K
K
University of California-Berkeley/U.S. Department of Agriculture, Albany 94710.
Franci
C
C
Parks
B M
BM
Seeley
K A
KA
Short
T W
TW
Tepperman
J M
JM
Quail
P H
PH
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism / Q000528:radiation effects; D001483:Base Sequence; D002874:Chromosome Mapping; D004247:DNA / Q000235:genetics; D017343:Genes, Plant; D008027:Light; D008969:Molecular Sequence Data; D009154:Mutation; D010834:Phytochrome / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
D012333:RNA, Messenger; D010834:Phytochrome; D004247:DNA