II.48 Nitrate reductase-deficient mutants in barley.
R. L. Warner, C. J. Lin, and A. Kleinhofs. Department of Agronomy and Soils and Program in Genetics, Washington State University, Pullman, Washington 99163, U.S A.
Most chlorophyll-deficient mutants in barley are also reduced in nitrate reductase activity (2), however, there are very few reports of nitrate reductase-less mutants in otherwise normal higher plants. Nitrate reductaseless or-deficient mutants would be useful for studying the regulation of nitrate reductase and eventually the role of nitrate reductase in total protein metabolism. Chlorate has been used to identify nitrate reductase-deficient mutants in Arabidopsis (1). We screened approximately 100,000 M3 seedlings from azide treated Steptoe barley for chlorate resistance in attempts to find nitrate reductase-deficient mutants. While a substantial number of M3 seedlings were more resistant to chlorate than the control seedlings, most were either chlorophyll deficient or had very poorly developed roots. Approximately 20 seedlings appeared to be somewhat chlorate resistant and normal in appearance, but none of these selections produced nitrate reductase-deficient descendants These selections are currently being retested for chlorate resistance.
Since screening with chlorate for nitrate reductase-deficient mutants was unsuccessful, we screened individual seedlings using a qualitative in vivo nitrate reductase assay technique. Approximately 25,000 M3 seedlings and 5,000 M2 seedlings were tested. To date, 7 seedlings have been found to be nitrate reductase-deficient. Three of these were sterile and produced no seed. One mutant has been confirmed as nitrate reductase deficient in the next generation. This mutant, designated Ax12 produced offspring that are normal green and have less than 1 percent of normal Steptoe nitrate reductase activity. Seeds from this and other mutants are currently being increased for further genetic and physiological studies.
References:
Oostindier-Braaksma, F.J., and W.J. Feenstra. 1973. Isolation and characterization of chlorate-resistant mutants of Arabidopsis thaliana. Mutation Research 19:175-185.
Warner, R.L. and A. Kleinhofs. 1974. Relationships between nitrate reductase, nitrite reductase, and ribulose diphosphate carboxylase activities in chlorophyll-deficient mutants of barley. Crop Science 14:654-658.