Molecular analysis of the waxy locus of Zea mays

The structure of the wild-type waxy (wx⁺) locus was determined by sequence analysis of both a genomic and an almost full-size cDNA clone. The coding region comprises 3,718 bp and is composed of 14 exons and 13 small introns. The exons and the promoter region are G/C rich (60%-80%). All three waxy transcripts analysed so far reveal different polyadenylation sites and corresponding polyadenylation signals. The smallest of these mRNAs has a size of 2,263 nucleotides. Northern blot analysis suggests that the tissue-specific expression of the locus is due to transcriptional control. The insertion sites of all transposable element induced waxy mutations analysed have been mapped precisely within the locus. N-terminal sequencing of the mature wx⁺ protein leads to the identification of a maize amyloplast-specific transit peptide of 72 aminoacid residues.