title: A conditional marker gene allowing both positive and negative selection in plants.
abstract: Selectable markers enable transgenic plants or cells to be identified after transformation. They can be divided into positive and negative markers conferring a selective advantage or disadvantage, respectively. We present a marker gene, dao1, encoding D-amino acid oxidase (DAAO, EC 1.4.3.3) that can be used for either positive or negative selection, depending on the substrate. DAAO catalyzes the oxidative deamination of a range of D-amino acids. Selection is based on differences in the toxicity of different D-amino acids and their metabolites to plants. Thus, D-alanine and D-serine are toxic to plants, but are metabolized by DAAO into nontoxic products, whereas D-isoleucine and D-valine have low toxicity, but are metabolized by DAAO into the toxic keto acids 3-methyl-2-oxopentanoate and 3-methyl-2-oxobutanoate, respectively. Hence, both positive and negative selection is possible with the same marker gene. The marker has been successfully established in Arabidopsis thaliana, and proven to be versatile, rapidly yielding unambiguous results, and allowing selection immediately after germination.
authors.forename: Oskar
authors.initials: O
authors.lastname: Erikson
authors.forename: Magnus
authors.initials: M
authors.lastname: Hertzberg
authors.forename: Torgny
authors.initials: T
authors.lastname: Näsholm
mesh_terms: D000409:Alanine / Q000737:chemistry; D017360:Arabidopsis / Q000235:genetics; D002384:Catalysis; D003605:D-Amino-Acid Oxidase / Q000737:chemistry; D004247:DNA / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D005819:Genetic Markers; D005821:Genetic Techniques; D005822:Genetic Vectors; D045782:Hemiterpenes; D007532:Isoleucine / Q000737:chemistry; D007651:Keto Acids / Q000737:chemistry; D010100:Oxygen / Q000378:metabolism; D010944:Plants / Q000235:genetics*; D030821:Plants, Genetically Modified; D012313:RNA / Q000737:chemistry; D012694:Serine / Q000737:chemistry; D019076:Transgenes; D014633:Valine / Q000737:chemistry
chemical_list: D005819:Genetic Markers; D045782:Hemiterpenes; D007651:Keto Acids; D007532:Isoleucine; C016211:alpha-keto-beta-methylvaleric acid; D012694:Serine; D012313:RNA; C001505:alpha-ketoisovalerate; D004247:DNA; D003605:D-Amino-Acid Oxidase; D014633:Valine; D000409:Alanine; D010100:Oxygen