Structural and transcriptional analysis of DNA sequences flanking genes that encode 19 kilodalton zeins.

The nucleotide sequence of gz19ab11, a clone that corresponds to the coding and flanking sequences of an Mr 19,000 alpha zein, was determined. Comparison of the DNA sequences flanking this gene with those of other members of the gene subfamily showed that sequence conservation extends 820 nucleotides into the 5' flanking region and 130 nucleotides into the 3' flanking region. Southern blot analysis of maize DNA indicated that highly repetitive sequences are located within 950 bp 5' and 300 bp 3' to the protein coding region of these genes. The coding region of gz19ab11 is similar to but not identical with cDNA clones corresponding to Mr 19,000 zeins, and analysis of zein transcripts indicated that this gene is expressed exclusively in endosperm tissue. RNAs which correspond to transcripts originating 60 nucleotides, and more than 800 nucleotides, upstream of the initiation codon were detected for this and a related gene. However, the concentration of the large RNA species was several orders of magnitude less than that of the shorter RNAs. The functional significance of these large RNA transcripts in zein gene expression is unclear.