Interaction of an embryo DNA binding protein with a soybean lectin gene upstream region.

Seed protein genes are highly regulated during the soybean life cycle. These genes encode prevalent mRNAs that accumulate and decay during embryogenesis, and are either undetectable or present at low levels in mature plant organ systems. Transcriptional activation and repression processes are important in regulating seed protein gene developmental expression programs. We started DNA binding protein studies with the soybean lectin gene to begin to identify trans-acting proteins and cis-regulatory sequences required for seed protein gene expression. We have identified an embryo DNA binding protein that interacts with specific sequences in the lectin gene 5' region. The DNA binding protein is undetectable in mature plant organ systems and its concentration parallels the lectin gene transcription rate during embryogenesis. The DNA binding protein activity corresponds to a 60,000 Mr (60K) nuclear protein, and a protein of similar size interacts with at least one other seed protein gene but not with a gene inactive during embryogenesis. Our data suggest that the 60K protein, and the DNA sequences that it interacts with, may be involved in regulating lectin gene expression.