title: Characterization of tryptophan-overproducing potato transgenic for a mutant rice anthranilate synthase alpha-subunit gene (OASA1D).
abstract: Potato plants (Solanum tuberosum cv. May Queen) transgenic for OASA1D, which encodes a point mutant of an alpha-subunit of rice (Oryza sativa) anthranilate synthase (AS, EC 4.1.3.27), were generated in order to determine the effects of the mutant gene on levels of free tryptophan (Trp) and AS activity in this important crop. Expression of OASA1D in potato induced a 2- to 20-fold increase in the amount of free Trp. This increase was likely due to a reduction in the sensitivity of AS containing the mutant alpha-subunit to feedback inhibition by Trp. Nontargeted metabolite profiling by high-performance liquid chromatography coupled with ultraviolet photodiode array detection as well as targeted profiling by liquid chromatography coupled with mass spectrometry revealed no marked changes in the levels of other metabolites, with the exception of indole-3-acetic acid (IAA), in the transgenic plants. The level of IAA in the upper part of the shoot was increased by a factor of 8.3-39, depending on the transgenic lines, with no detectable effect on plant growth or development. The effects of transformation thus appeared limited to the biosynthesis of Trp and IAA, with the overall metabolic network in potato being virtually unaffected. These results suggest that transformation with OASA1D may prove effective for the breeding of crops with an increased level of free Trp.
authors.affiliation: Plant functions and their control, CREST, Japan Science and Technology Agency, 3-4-5 Nihonbashi, Chuo, Tokyo 103-0027, Japan.
authors.forename: Fumio
authors.initials: F
authors.lastname: Matsuda
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Yamada
authors.forename: Haruna
authors.initials: H
authors.lastname: Miyazawa
authors.forename: Hisashi
authors.initials: H
authors.lastname: Miyagawa
authors.forename: Kyo
authors.initials: K
authors.lastname: Wakasa
mesh_terms: D000878:Anthranilate Synthase / Q000235:genetics* / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism; D015394:Molecular Structure; D012275:Oryza / Q000201:enzymology* / Q000235:genetics*; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics; D035281:Plant Tubers / Q000201:enzymology / Q000235:genetics; D030821:Plants, Genetically Modified; D017354:Point Mutation; D021122:Protein Subunits; D011198:Solanum tuberosum / Q000235:genetics* / Q000378:metabolism; D014364:Tryptophan / Q000096:biosynthesis*
chemical_list: D007210:Indoleacetic Acids; D021122:Protein Subunits; C030737:indoleacetic acid; D014364:Tryptophan; D000878:Anthranilate Synthase