AbstractBz‐wmis an allele of theBzlocus of maize isolated by McClintock (1962) as a derivative ofbz‐m2It contains aDs1insertion 63 bp upstream of the start of transcription and a 3 bp insertion in the coding region at the site of theAcelement that was present inbz‐m2. Bz‐wmproduces, in the aleurone layer of the endosperm, low amounts (∼1 of wild‐type) of a Bz‐gene encoded UDP‐glucose: flavoid 3‐0‐glucosyltransferase (UFGT) polypeptide with altered thermal stability. Three phenotypically wild‐type derivatives,Bz' (wm)‐1, Bz' (wm)‐2 and Bz' (wm)‐3, were isolated in the presence ofAcand shown to have excised theDs1element but not fully restored UFGT activity in endosperm assays. In the studies reported here, we have further analyzed theseBz'derivatives ofBz‐wmby determining the DNA sequences left behind onDs1excision, and by measuring the amount of UFGT activity and/orBzmRNA conditioned byBz‐wmand theBz'derivatives in different tissues. The data indicate that tissue‐specific differences in expression of theBzgene have been produced in alleles with mutations caused by transposable elementsAcand Ds. These mutations may affect either the amount ofBztranscription or the stability of the UFGT polypeptide. The sequence or spacing in the ‐63 region of theBzpromoter appears to be critical for maximum expression in aleurone and husk but not in p
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