THE LIGHT-REGULATED ARABIDOPSIS BZIP TRANSCRIPTION FACTOR GENE ATB2 ENCODES A PROTEIN WITH AN UNUSUALLY LONG LEUCINE-ZIPPER DOMAIN

A light-regulated basic domain/leucine zipper gene, ATB2, was identifi ed in an Arabidopsis thaliana transcription factor gene collection. Bo th genomic and cDNA clones of ATB2 were isolated. The gene encodes a s mall protein (18 kDa) which mainly consists of the basic domain and an unusually long leucine zipper. The expression of the ATB2 gene is ind uced when etiolated or dark-adapted seedlings are transferred to the l ight. Moreover, its expression is derepressed in dark-grown seedlings of the photomorphogenic mutants cop1 and det1. In mature plants, trans cript levels are particularly high in flowers and also light-responsiv e in these tissues.