title: GLYCOALKALOID METABOLISM1 is required for steroidal alkaloid glycosylation and prevention of phytotoxicity in tomato.
abstract: Steroidal alkaloids (SAs) are triterpene-derived specialized metabolites found in members of the Solanaceae family that provide plants with a chemical barrier against a broad range of pathogens. Their biosynthesis involves the action of glycosyltransferases to form steroidal glycoalkaloids (SGAs). To elucidate the metabolism of SGAs in the Solanaceae family, we examined the tomato (Solanum lycopersicum) GLYCOALKALOID METABOLISM1 (GAME1) gene. Our findings imply that GAME1 is a galactosyltransferase, largely performing glycosylation of the aglycone tomatidine, resulting in SGA production in green tissues. Downregulation of GAME1 resulted in an almost 50% reduction in α-tomatine levels (the major SGA in tomato) and a large increase in its precursors (i.e., tomatidenol and tomatidine). Surprisingly, GAME1-silenced plants displayed growth retardation and severe morphological phenotypes that we suggest occur as a result of altered membrane sterol levels caused by the accumulation of the aglycone tomatidine. Together, these findings highlight the role of GAME1 in the glycosylation of SAs and in reducing the toxicity of SA metabolites to the plant cell.
authors.affiliation: Department of Plant Sciences, Weizman Institute of Science, Rehovot, Israel.
authors.forename: Maxim
authors.initials: M
authors.lastname: Itkin
authors.forename: Ilana
authors.initials: I
authors.lastname: Rogachev
authors.forename: Noam
authors.initials: N
authors.lastname: Alkan
authors.forename: Tally
authors.initials: T
authors.lastname: Rosenberg
authors.forename: Sergey
authors.initials: S
authors.lastname: Malitsky
authors.forename: Laura
authors.initials: L
authors.lastname: Masini
authors.forename: Sagit
authors.initials: S
authors.lastname: Meir
authors.forename: Yoko
authors.initials: Y
authors.lastname: Iijima
authors.forename: Koh
authors.initials: K
authors.lastname: Aoki
authors.forename: Ric
authors.initials: R
authors.lastname: de Vos
authors.forename: Dov
authors.initials: D
authors.lastname: Prusky
authors.forename: Saul
authors.initials: S
authors.lastname: Burdman
authors.forename: Jules
authors.initials: J
authors.lastname: Beekwilder
authors.forename: Asaph
authors.initials: A
authors.lastname: Aharoni
mesh_terms: D000470:Alkaloids / Q000378:metabolism*; D001483:Base Sequence; D020231:Colletotrichum / Q000472:pathogenicity; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005030:Ethylenes; D005638:Fruit / Q000254:growth & development / Q000378:metabolism; D005700:Galactosyltransferases / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D017343:Genes, Plant; D006031:Glycosylation; D018551:Solanum lycopersicum / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D055442:Metabolome; D008969:Molecular Sequence Data; D010641:Phenotype; D010840:Phytosterols / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014053:Tomatine / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D000470:Alkaloids; D005030:Ethylenes; D008565:Membrane Proteins; D010840:Phytosterols; D010940:Plant Proteins; D011994:Recombinant Proteins; C003677:tomatidine; D014053:Tomatine; C036216:ethylene; D005700:Galactosyltransferases