DEVELOPMENTAL AND HORMONAL-REGULATION OF SUNFLOWER HELIANTHININ GENES- PROXIMAL PROMOTER SEQUENCES CONFER REGIONALIZED SEED EXPRESSION

DNA elements involved in the regulation of two sunflower helianthinin genes were identified by analysis of beta-glucuronidase (GUS) expressi on in transgenic tobacco driven by sequences derived from the 5' upstr eam regions of these genes. A 2.4-kb upstream region of the helianthin in gene HaG3-A conferred rigorous developmental GUS expression in tran sgenic tobacco seeds with no significant GUS activity in nonembryonic tissues. Regions of the helianthinin upstream regulatory ensemble (URE ) conferred ectopic expression in nonembryonic tissues when analyzed o utside of the context of the complete helianthinin regulatory complex. A proximal promoter region was identified that conferred significant GUS expression in seeds but not in leaves of transgenic tobacco. Three sequence motifs that bind to seed nuclear proteins were identified in the proximal promoter region; mutations in these motifs significantly reduced the level of nuclear protein binding. Another important class of cis-regulatory elements was identified in the helianthinin URE tha t conferred abscisic acid-responsive GUS expression. In the full-lengt h helianthinin URE, these elements only responded to abscisic acid in the developing seed, suggesting that the helianthinin gene contains ad ditional regulatory elements, possibly in the proximal promoter region , that ensure hierarchical control in the developing seed.