THE ARABIDOPSIS PHYTOCHROME-A GENE HAS MULTIPLE TRANSCRIPTION START SITES AND A PROMOTER SEQUENCE MOTIF HOMOLOGOUS TO THE REPRESSOR ELEMENTOF MONOCOT PHYTOCHROME-A GENES

We have determined the sequence of the phytochrome A gene (PHYA) and i ts flanking DNA from Arabidopsis thaliana and have identified transcri ption start sites for three nested transcripts of increasing length. T he overall structure of the gene is similar as regards exon/intron org anization to other angiosperm PHY genes characterized. The triple tran scription start site arrangement is similar to that of pea PHYA but di fferent from the single start site of oat, rice and maize PHYA genes, indicating a possible monocot-dicot difference. Comparison of the Arab idopsis PHYA promoter sequence with others available indicates that bo th pea and Arabidopsis promoters contain a DNA element with a core seq uence motif identical to one conserved in all existing monocot PHYA se quences and defined by functional assay in the oat PHYA gene as repres sor element, RE1, responsible for negative light regulation.