Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: July 20, 2005
Publication Date: July 16, 2005
Citation: Pinkerton, T.S., Dowd, P.F. 2005. Molecular characterization of genes encoding anthranilate synthase from blue fluorescent mutants Bf-1 and Bf-2 of maize [abstract]. American Society of Plant Biologists Annual Meeting. Abstract No. 589. Technical Abstract: Tryptophan plays an important role in plants not only as an amino acid for polypeptide production, but also as a precursor for secondary metabolites. Seeds of an L289xI205 cross were exposed to radiation from a nuclear test in 1946. Several mutants were described by Anderson et al., including two with a blue fluorescence phenotype. The first mutant, Bf-1, has been shown to accumulate anthranilic acid and related compounds which fluoresce under UV illumination. Bf-1 also has a distinct grape odor, due to the accumulation of methylanthranilate. Genetic crosses isolated the Bf-1 to chromosome 9. A second mutant, Bf-2, was also identified, but the gene was located on chromosome 10. Both mutants have altered tryptophan metabolism and appear to be insensitive to allosteric regulation of anthranilate synthase by tryptophan and its analogs. The resistance to allosteric regulation by tryptophan derivatives coupled with the fluorescence and odor phenotypes make Bf-1 and Bf-2 of interest as potential marker genes. Initial results in the sequencing of anthranilate synthase gene from cDNA of the Bf-1 mutant indicates a single amino acid change to a residue conserved across all known anthranilate synthases may be responsible for the change in sensitivity to allosteric regulation. This mutation appears to be in the allotsteric tryptophan binding region of the alpha-subunit of anthranilate synthase and differs from previously described mutants in other plant species. In order to validate the impact of the mutant, mutagenesis introducing the identified mutation was carried out on wild-type anthranilate synthase gene from Pseudomonas syringae pv. phaseolicola. This mutant was tested for resistance to 5-methyltryptophan when expressed in Escherichia coli. Sequencing of the Bf-2 mutant will also be presented.