Three alcohol dehydrogenase genes in wild and cultivated barley: characterization of the products of variant alleles.

Barley (Hordeum vulgare) and its wild progenitor (H. spontaneum) have three loci for alcohol dehydrogenase (EC 1.1.1.1; ADH). The Adh1 locus is constitutively expressed in seed tissues, whereas expression of the loci Adh2 and Adh3 requires anaerobic induction. The Adh3 gene is well expressed in aleurone and embryo tissues kept under N2 for 2-3 days. Using N2-treated embryos, a diverse collection of H. spontaneum was screened in starch gels for electrophoretic variants at the Adh3 locus. Four variants were found: two were conventional mobility variants (Adh3 S, Adh3 V); one was a null variant (Adh3 n); and the fourth (Adh3 I) variant lacked active homodimers and showed reduced heterodimer activity. The 35S-labeled monomers induced under N2 in the lines homozygous for Adh1, Adh2, or Adh3 variants were immunoprecipitated with antiserum raised against maize ADH. Fluorography after separation by SDS-PAGE and by urea-isoelectric focusing indicated that the Adh3 n allele was CRM- and that the Adh3 I gene product was smaller than normal. The Adh1 and Adh3 variants showed independent segregation.