THE PLANT CELL, Vol 6, Issue 4 473-486, Copyright © 1994 by American Society of Plant Biologists
Developmental and Hormonal Regulation of Sunflower Helianthinin Genes: Proximal Promoter Sequences Confer Regionalized Seed Expression
A. N. Nunberg, Z. Li, M. A. Bogue, J. Vivekananda, A. S. Reddy and T. L. Thomas
Department of Biology, Texas A & M University, College Station, Texas 77843
DNA elements involved in the regulation of two sunflower helianthinin genes
were identified by analysis of [beta]-glucuronidase (GUS) expression in
transgenic tobacco driven by sequences derived from the 5[prime] upstream
regions of these genes. A 2.4-kb upstream region of the helianthinin gene
HaG3-A conferred rigorous developmental GUS expression in transgenic
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 outside 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 that conferred abscisic
acid-responsive GUS expression. In the full-length helianthinin URE, these
elements only responded to abscisic acid in the developing seed, suggesting
that the helianthinin gene contains additional regulatory elements,
possibly in the proximal promoter region, that ensure hierarchical control
in the developing seed.
