Figure 3.

Positional identification of the HY1 locus. The genetic map of chromosome 2 as viewed from the A. thaliana DNA database defined the genetic position of HY1 as linked to ER. Assembly of the physical map of the ER contig by overlapping genomic bacteria artificial chromosome clones identified the exact position of ER and two possible candidate genes for HY1 (AtHO1 and 2) based on its expected homology to Synechocystis HOs. The gene structure of AtHO1 was deduced by comparing the genomic sequence with that of a full-length cDNA. Open and solid boxes denote coding region and untranslated regions, respectively. Lines indicate introns and nontranscribed regions. DNA sequences surrounding the position of the three hy1 mutations are indicated and aligned with the wild-type (HY1) AtHO1 sequence. Underlined nucleotides denote sequence differences between wild type and the mutants. Upper- and lowercase letters represent exon and intron sequences, respectively.