Tissue culture isolation of a second mutant locus for increased threonine accumulation in maize

• Published in: Theoretical and applied genetics 1990-02, Vol.79 (2), p.209-215
• Main Authors: Diedrick, T.J, Frisch, D.A, Gengenbach, B.G
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; alleles; amino acids; Biological and medical sciences; biosynthesis; Classical and quantitative genetics; Classical and quantitative genetics. Population genetics. Molecular genetics; Classical genetics, quantitative genetics, hybrids; Fundamental and applied biological sciences. Psychology; Generalities. Genetics. Plant material; Genetics and breeding of economic plants; Genetics of eukaryotes. Biological and molecular evolution; heterozygosity; kinases; loci; lysine; mutants; Pteridophyta, spermatophyta; threonine; tissue culture; Vegetals; Zea mays
• ISSN: 0040-5752; 1432-2242
• DOI: 10.1007/BF00225953

Regenerable maize (Zea mays L.) tissue cultures were selected for ability to grow in the presence of inhibitory (1.0-1.5 mM) concentrations of L-lysine plus L-threonine. Testcross kernels from one regenerated plant (LT20) segregated for wild-type and high free threonine concentration in a 1∶1 ratio consistent with a single dominant gene for high free threonine. Free threonine concentrations (nmol/mg dry weight) increased an average of 29-fold in bulked F2 kernel samples from heterozygous mutant plants, and the total (free plus protein-bound) threonine concentration increased 68%. Increases in protein-bound methionine, lysine and glycine concentrations were also noted, suggesting a possible effect of the mutation on protein concentration and composition. Allelism tests with a previously selected mutant line, Ltr (*)19, showed that two unlinked, codominant genes conditioned the high free threonine phenotype. Based on a separate study of aspartate kinase feedback inhibition characteristics in the two mutant lines, we propose that the mutant alleles [gene and allele designations are according to guidelines for maize genetic nomenclature (Burnham et al. 1975)] be designated Ask-LT19 and Ask2-LT20 for the Ltr (*)19 and LT20 mutants, respectively.