title: The relative contribution of genes operating in the S-methylmethionine cycle to methionine metabolism in Arabidopsis seeds.
abstract: Enzymes operating in the S -methylmethionine cycle make a differential contribution to methionine synthesis in seeds. In addition, mutual effects exist between the S -methylmethionine cycle and the aspartate family pathway in seeds. Methionine, a sulfur-containing amino acid, is a key metabolite in plant cells. The previous lines of evidence proposed that the S-methylmethionine (SMM) cycle contributes to methionine synthesis in seeds where methionine that is produced in non-seed tissues is converted to SMM and then transported via the phloem into the seeds. However, the relative regulatory roles of the S-methyltransferases operating within this cycle in seeds are yet to be fully understood. In the current study, we generated transgenic Arabidopsis seeds with altered expression of three HOMOCYSTEINE S-METHYLTRANSFERASEs (HMTs) and METHIONINE S-METHYLTRANSFERASE (MMT), and profiled them for transcript and metabolic changes. The results revealed that AtHMT1 and AtHMT3, but not AtHMT2 and AtMMT, are the predominant enzymes operating in seeds as altered expression of these two genes affected the levels of methionine and SMM in transgenic seeds. Their manipulations resulted in adapted expression level of genes participating in methionine synthesis through the SMM and aspartate family pathways. Taken together, our findings provide new insights into the regulatory roles of the SMM cycle and the mutual effects existing between the two methionine biosynthesis pathways, highlighting the complexity of the metabolism of methionine and SMM in seeds.
authors.affiliation: Laboratory of Plant Science, Migal Galilee Technology Center, 12100, Kiryat Shmona, Israel.|Faculty of Biology, Technion-Israel Institute of Technology, 32000, Haifa, Israel.
authors.forename: Hagai
authors.initials: H
authors.lastname: Cohen
authors.affiliation: Laboratory of Plant Science, Migal Galilee Technology Center, 12100, Kiryat Shmona, Israel.|Tel-Hai College, 11016, Upper Galilee, Israel.
authors.forename: Asaf
authors.initials: A
authors.lastname: Salmon
authors.affiliation: Gilat Volcani Center, Agricultural Research Organization (ARO), Negev, Israel.
authors.forename: Zipora
authors.initials: Z
authors.lastname: Tietel
authors.affiliation: Laboratory of Plant Science, Migal Galilee Technology Center, 12100, Kiryat Shmona, Israel.
authors.forename: Yael
authors.initials: Y
authors.lastname: Hacham
authors.affiliation: Laboratory of Plant Science, Migal Galilee Technology Center, 12100, Kiryat Shmona, Israel. rachel@migal.org.il.|Tel-Hai College, 11016, Upper Galilee, Israel. rachel@migal.org.il.
authors.forename: Rachel
authors.initials: R
authors.lastname: Amir
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D008715:Methionine / Q000031:analogs & derivatives / Q000378:metabolism*; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000378:metabolism*; D014814:Vitamin U / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D014814:Vitamin U; D008715:Methionine; C038344:methionine methyl ester; D008780:Methyltransferases; C093871:methionine S-methyltransferase
keywords: Arabidopsis thaliana; HOMOCYSTEINE S-METHYLTRANSFERASE; METHIONINE S-METHYLTRANSFERASE; Methionine; S-Methylmethionine; Transgenic seeds