Functional alcohol dehydrogenase mutants of Saccharomyces cerevisiae conferring temperature-conditional allyl alcohol resistance

An efficient selection producing structural gene mutants of yeast alcohol dehydrogenase resistant to pyrazole

Selection for resistance to allyl alcohol in respiration-incompetent Saccharomyces cerevisiae produces a high proportion of mutants that can be localized within the ADH2 structural gene and that still, because of the type of selection employed, retain enzyme activity. We show here that a similar type of selection produces a similarly high proportion of mutants resistant to the competitive inhibitor pyrazole. The first four mutants examined, picked at random from a collection of spontaneous pyrazole-resistant mutants, show altered--usually increased--KM values for ethanol and NAD+, and markedly increased K1 values for pyrazole, compared with the wild type. When these kinetic measures and their electrophoretic mobilities were compared, all the mutants could be clearly distinguished from each other as well as from wild type. Genetic analysis shows these mutants to be close to and probably resident in the structural gene. For a variety of reasons, these mutants are even more favorable subjects for population genetic analysis and the dissection of molecular microevolution than are allyl alcohol-resistant mutants.

Isolation and biochemical analysis of ethyl methanesulfonate-induced alcohol dehydrogenase null mutants of arabidopsis thaliana (L.) Heynh

Several mutants have been isolated at the Arabidopsis thaliana (L.) Heynh. alcohol dehydrogenase (ADH) gene locus using allyl alcohol selection on ethyl methanesulfonate (EMS)-mutagenized seeds. Eleven mutants were isolated in the ADH1-A electrophoretic allele, and 21 in the ADH1-S allele. These null mutants are characterized by the absence of measurable ADH activity and genetic data showed that the mutations were confined to the ADH1 gene locus of Arabidopsis. Eleven mutants in the ADH1-A background were further characterized at the protein and mRNA level. These experiments revealed striking differences in the ADH protein and mRNA content. Some of the mutants did not synthesize any mRNA or ADH-like protein, whereas some of them had a nearly normal level of ADH protein and mRNA. Others had a very low level of both protein and mRNA. ADH null mutants differed physiologically from the wild type by their higher sensitivity to anaerobic treatment in plants and significantly reduced resistance to acetaldehyde in suspension cultures.