title: Nodule-enhanced expression of a sucrose phosphate synthase gene member (MsSPSA) has a role in carbon and nitrogen metabolism in the nodules of alfalfa (Medicago sativa L.).
abstract: Sucrose phosphate synthase (SPS) catalyzes the first step in the synthesis of sucrose in photosynthetic tissues. We characterized the expression of three different isoforms of SPS belonging to two different SPS gene families in alfalfa (Medicago sativa L.), a previously identified SPS (MsSPSA) and two novel isoforms belonging to class B (MsSPSB and MsSPSB3). While MsSPSA showed nodule-enhanced expression, both MsSPSB genes exhibited leaf-enhanced expression. Alfalfa leaf and nodule SPS enzymes showed differences in chromatographic and electrophoretic migration and differences in V (max) and allosteric regulation. The root nodules in legume plants are a strong sink for photosynthates with its need for ATP, reducing power and carbon skeletons for dinitrogen fixation and ammonia assimilation. The expression of genes encoding SPS and other key enzymes in sucrose metabolism, sucrose phosphate phosphatase and sucrose synthase, was analyzed in the leaves and nodules of plants inoculated with Sinorhizobium meliloti. Based on the expression pattern of these genes, the properties of the SPS isoforms and the concentration of starch and soluble sugars in nodules induced by a wild type and a nitrogen fixation deficient strain, we propose that SPS has an important role in the control of carbon flux into different metabolic pathways in the symbiotic nodules.
authors.affiliation: Graduate Program in Molecular Biology, New Mexico State University, Las Cruces, NM 88003, USA.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Aleman
authors.forename: Jose Luis
authors.initials: JL
authors.lastname: Ortega
authors.forename: Martha
authors.initials: M
authors.lastname: Martinez-Grimes
authors.forename: Mark
authors.initials: M
authors.lastname: Seger
authors.forename: Francisco Omar
authors.initials: FO
authors.lastname: Holguin
authors.forename: Diana J
authors.initials: DJ
authors.lastname: Uribe
authors.forename: David
authors.initials: D
authors.lastname: Garcia-Ibilcieta
authors.forename: Champa
authors.initials: C
authors.lastname: Sengupta-Gopalan
mesh_terms: D000494:Allosteric Regulation / Q000235:genetics; D015153:Blotting, Western; D050260:Carbohydrate Metabolism / Q000235:genetics; D002244:Carbon / Q000378:metabolism*; D002852:Chromatography, Ion Exchange; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D005964:Glucosyltransferases / Q000235:genetics*; D000455:Medicago sativa / Q000201:enzymology* / Q000235:genetics* / Q000382:microbiology; D005810:Multigene Family; D009584:Nitrogen / Q000378:metabolism*; D009586:Nitrogen Fixation / Q000235:genetics; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D053204:Root Nodules, Plant / Q000201:enzymology* / Q000235:genetics / Q000382:microbiology; D016962:Sinorhizobium meliloti / Q000502:physiology; D012995:Solubility; D013213:Starch / Q000378:metabolism; D013559:Symbiosis / Q000235:genetics
chemical_list: D010940:Plant Proteins; D012333:RNA, Messenger; D002244:Carbon; D013213:Starch; D005964:Glucosyltransferases; C022698:sucrose-phosphate synthase; D009584:Nitrogen