THE PLANT CELL, Vol 1, Issue 9 855-866, Copyright © 1989 by American Society of Plant Biologists
A Sunflower Helianthinin Gene Upstream Sequence Ensemble Contains an Enhancer and Sites of Nuclear Protein Interaction
J. Jordano, C. Almoguera and T. L. Thomas
Department of Biology, Texas A&M University, College Station, Texas 77843-3258
Genes encoding helianthinin, the major seed protein in sunflower, are
highly regulated. We have identified putative cis-acting and trans-acting
elements that may function in the control of helianthinin expression. A
404-base pair DNA fragment of the sunflower helianthinin gene HaG3D,
located 322 base pairs from the transcriptional start site, enhanced
[beta]-glucuronidase expression in transgenic tobacco embryos. Sequences
within this fragment were found to bind nuclear proteins present in both
sunflower embryo and hypocotyl nuclear extracts. The binding site was
localized by phenanthroline-copper ion footprinting experiments to A/T-rich
sequences located from -705 to -654. Binding competition experiments
revealed that these sunflower proteins also bind to upstream promoter
sequences from another helianthinin gene (HaG3A) and two other plant
embryo-specific genes, carrot DcG3 and French bean phaseolin. However,
sequences of the cauliflower mosaic virus 35S promoter/enhancer complex
failed to compete for its binding. Phenanthroline-copper ion footprinting
experiments showed that the binding sites for the sunflower proteins in
HaG3A (-1463 to -1514 and -702 to -653) and in phaseolin (-671 to -627) are
also very A/T-rich, have similar sizes, and are located at similar
distances from their respective promoters.
