title: The catabolic enzyme methionine gamma-lyase limits methionine accumulation in potato tubers.
abstract: Increasing methionine in potato tubers is desirable, both to increase the availability of this limiting essential amino acid and to enhance the aroma of baked and fried potatoes. Previous attempts to elevate potato methionine content using transgenic approaches have focused on increasing methionine biosynthesis. Higher isoleucine accumulation in these transgenic tubers suggested that the potatoes compensate for increased methionine biosynthesis with enhanced catabolism via methionine gamma-lyase (MGL), thereby producing 2-ketybutyrate for isoleucine biosynthesis. In the current study, we show that potato StMGL1 encodes a functional MGL in potato tubers. In planta silencing of StMGL1 results in an increased methionine to isoleucine ratio in the free amino acid profile of potato tubers and, in some transgenic lines, elevated accumulation of free methionine. In both wild-type and transgenic tubers, the ratio of methionine to isoleucine is negatively correlated with the level of StMGL1 transcript. A three-dimensional distribution of free amino acids in potato tubers is also described.
authors.affiliation: Boyce Thompson Institute for Plant Research, Ithaca, NY, USA.
authors.forename: Tengfang
authors.initials: T
authors.lastname: Huang
authors.forename: Vijay
authors.initials: V
authors.lastname: Joshi
authors.forename: Georg
authors.initials: G
authors.lastname: Jander
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism; D013437:Carbon-Sulfur Lyases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D007532:Isoleucine / Q000378:metabolism; D008715:Methionine / Q000378:metabolism*; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D035281:Plant Tubers / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000378:metabolism; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D016415:Sequence Alignment; D011198:Solanum tuberosum / Q000254:growth & development / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D010940:Plant Proteins; D012333:RNA, Messenger; D007532:Isoleucine; D008715:Methionine; D013437:Carbon-Sulfur Lyases; C021558:L-methionine gamma-lyase
keywords: amino acid; methionine; methionine gamma-lyase; potato; silencing; tuber