ANALYSIS OF AN ABSCISIC-ACID (ABA)-RESPONSIVE GENE PROMOTER BELONGINGTO THE ASR GENE FAMILY FROM TOMATO IN HOMOLOGOUS AND HETEROLOGOUS SYSTEMS

Asr is a family of genes that maps to chromosome 4 of tomato. Asr2, a recently reported member of this family, is believed to be regulated b y abscisic acid (ABA), stress and ripening. A genomic Asr2 clone has b een fully sequenced, and candidate upstream regulatory elements have b een identified. To prove that the promoter region is functional in viv o, we fused it upstream of the beta-glucuronidase (GUS) reporter gene. The resulting chimeric gene fusion was used for transient expression assays in papaya embryogenic calli and leaves. In addition, the same c onstruct was used to produce transgenic tomato, papaya, tobacco, and p otato plants. Asr2 upstream sequences showed promoter function in all of these systems. Under the experimental conditions tested, ABA stimul ated GUS expression in papaya and tobacco, but not in tomato and potat o systems.