Isolation and characterization of UMP synthase mutants from haploid cell suspensions of Nicotiana tabacum

• Published in: Plant physiology (Bethesda) 1992-07, Vol.99 (3), p.1216-1225
• Main Authors: Santoso, D. (Iowa State University, Ames, IA), Thornburg, R.W
• Format: Article
• Language: English
• Subjects: ACTIVIDAD ENZIMATICA; ACTIVITE ENZYMATIQUE; Agronomy. Soil science and plant productions; Amino acids; Biological and medical sciences; Biotechnology; CAL; CALLO; Callus; Cell growth; Cell lines; CRECIMIENTO; CROISSANCE; CULTIVO DE CELULAS; CULTURE DE CELLULE; Cultured cells; Enzyme activity; Enzymes; Fundamental and applied biological sciences. Psychology; HAPLOIDIA; HAPLOIDIE; Haploidy; LIGASAS; LIGASE; MEDIO DE CULTIVO; Metabolism; MILIEU DE CULTURE; Molecular Biology and Gene Regulation; MUTANT; MUTANTES; NICOTIANA TABACUM; NUCLEOTIDE; NUCLEOTIDOS; Plant cells; Plant physiology and development; Plants; SELECCION; SELECTION; TECHNIQUE ANALYTIQUE; TECNICAS ANALITICAS
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.99.3.1216

Uridine 5'-monophosphate (UMP) synthase mutants of tobacco have been produced from haploid cell-suspension cultures of a transgenic Nicotiana tabacum line, Tr25. The mutants were induced by incubating the suspension-cultured cells with 1 mM N-nitroso-N-methylurea for either 5 or 12 hours. Twenty mutant calli were isolated on selection medium containing 20 milligrams per liter of 5-fluoroorotic acid. Of those tested, most had reduced regeneration capacity. Characterization of UMP synthase activities in the isolated calli showed that UMP synthase activity varied from 8 to nearly 100% of the wild-type activity. The growth of the calli on the media containing different levels of 5-fluoroorotic acid correlated with decreasing UMP synthase activity. Because the UMP synthase enzyme has two separate enzymic activities (orotate phosphoribosyl transferase and orotidine-5'-monophosphate decarboxylase), several mutants were further characterized to determine how the mutations affected each of the two enzymic activities. In each case, the enzymic activity affected was the orotate phosphoribosyl transferase and not the orotidine-5'-monophosphate decarboxylase. The wound-inducible phenotype of the Tr25 plants as measured by the activation of the pin2-CAT gene remained unchanged by introduction of the UMP synthase mutations