Plant Genome I Conference
Town & Country Conference Center, San Diego, CA, November, 1992.
PG-I: 51pg1
THE HY3 LOCUS IN ARABIDOPSIS IS THE GENE ENCODING PHYTOCHROME
B.
Jason W. Reed, Punita Nagpal, Daniel S. Pole, Masaki Furuya, and
Joanne Chory, Plant Biology Laboratory, The Salk Institute, La
Jolla, CA 92037, Laboratory of Plant Biological Regulation,
Frontier Research Programs, RIKEN Institute, Wako-shi, Saitama
351-01, Japan.
The long hypocotyl-3(hy3) mutant of Arabidopsis thaliana was
identified based on its long hypocotyl phenotype when grown in
white light. It lacks some of the known red and far red light
responses, and also accumulates less chlorophyll, and has fewer
chloroplasts per mesophyll cell than wild-type. This suggests
that the hy3 locus encodes a gene product necessary for the
perception or transduction of red/far red light signals. These
are known to be mediated by the phytochrome photoreceptors, which
are encoded by a small family of genes in Arabidopsis. We have
shown that a RFLP in the 5' untranslated region of the
phytochrome B cDNA from Arabidopsis cosegregates with a hy3
mutation. Mutations in the PHYB gene have been detected in all
five of the alleles examined. The mutant allele conferring the
least severe hypocotyl phenotype had a missense mutation while
the other more severe alleles had nonsense mutations or a T-DNA
insertion. These are the first mutations shown to fall in a
plant photoreceptor gene. In addition, PHYB function can be
inferred from the hy3 phenotypes. Along with the phenotypes
mentioned above, hy3 mutants have elongated hypocotyls, petioles,
root hairs, and flowering bolts. Thus, PHYB must act in numerous
tissues throughout development to affect cell elongation and
physiological processes in Arabidopsis.
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