title: Quality traits of conventional and transgenic lettuce (Lactuca sativa L.) at harvesting by NMR metabolic profiling.
abstract: Metabolism of genetically modified (GM) lettuce (Lactuca sativa L.) leaves was investigated by comparing NMR metabolic profiles of three lines (T(3)B12, T(7)B7, and T(7)B14) overexpressing the E. coli asparagine synthetase A gene with those of the wild type (WT) at 24, 56, and 64 days after sowing (DAS). Statistical analyses based on hydro-soluble compound profiles significantly and maximally discriminated the WT from GM-lines at optimal harvest time (56 DAS). The T(7)B14 metabolic variations were opposite to those of both T(3)B12/T(7)B7 lines, suggesting that unexpected effects of transgenesis had occurred. Compared to controls, the T(3)B12/T(7)B7 plants shared the leaf mass increase, higher amino acid (asparagine, glutamine, valine, and isoleucine) and protein levels, and lower nitrate contents, accompanied by a modest sink of organic acids (alpha-chetoglutarate, succinate, fumarate, and malate), sucrose, fructose, and inulins. Incongruously, the T(7)B14 butter heads were less leafy than the controls and showed lowered amino acid/protein contents and overstored inulin. To further investigate the metabolic discrepancies among the GM-lines, a set of key nitrogen and inulin genes was monitored. The T(3)B12/T(7)B7 lines shared comparable gene expression changes, including the induction of the endogenous asparagine synthetase1 and nitrate reductase1 that supported the targeted enhancement of nitrogen status. Transgene product malfunctioning and T-DNA rearrangements throughout generations were proposed to explain the decreased asparagine content and the complex expression pattern of N genes in T(7)B14 leaves. In the latter, the inulin accumulation was associated with the upregulation of fructan biosynthesis genes and the intense repression of fructan hydrolases.
authors.affiliation: Laboratorio di Risonanza Magnetica Annalaura Segre-CNR, Istituto di Metodologie Chimiche, 00015 Monterotondo Scalo, Rome, Italy.
authors.forename: Anatoly P
authors.initials: AP
authors.lastname: Sobolev
authors.forename: Giulio
authors.initials: G
authors.lastname: Testone
authors.forename: Flavio
authors.initials: F
authors.lastname: Santoro
authors.forename: Chiara
authors.initials: C
authors.lastname: Nicolodi
authors.forename: Maria A
authors.initials: MA
authors.lastname: Iannelli
authors.forename: Maria E
authors.initials: ME
authors.lastname: Amato
authors.forename: Antonietta
authors.initials: A
authors.lastname: Ianniello
authors.forename: Elvino
authors.initials: E
authors.lastname: Brosio
authors.forename: Donato
authors.initials: D
authors.lastname: Giannino
authors.forename: Luisa
authors.initials: L
authors.lastname: Mannina
mesh_terms: D000596:Amino Acids / Q000032:analysis / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D018545:Lactuca / Q000737:chemistry* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D055442:Metabolome; D018515:Plant Leaves / Q000737:chemistry / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D010940:Plant Proteins / Q000032:analysis / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000737:chemistry* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D010940:Plant Proteins