title: Deletions of the SACPD-C locus elevate seed stearic acid levels but also result in fatty acid and morphological alterations in nitrogen fixing nodules.
abstract: BACKGROUND
  Soybean (Glycine max) seeds are the primary source of edible oil in the United States. Despite its widespread utility, soybean oil is oxidatively unstable. Until recently, the majority of soybean oil underwent chemical hydrogenation, a process which also generates trans fats. An alternative to chemical hydrogenation is genetic modification of seed oil through identification and introgression of mutant alleles. One target for improvement is the elevation of a saturated fat with no negative cardiovascular impacts, stearic acid, which typically constitutes a minute portion of seed oil (~3%).
  
  
  RESULTS
  We examined radiation induced soybean mutants with moderately increased stearic acid (10-15% of seed oil, ~3-5 X the levels in wild-type soybean seeds) via comparative whole genome hybridization and genetic analysis. The deletion of one SACPD isoform encoding gene (SACPD-C) was perfectly correlated with moderate elevation of seed stearic acid content. However, SACPD-C deletion lines were also found to have altered nodule fatty acid composition and grossly altered morphology. Despite these defects, overall nodule accumulation and nitrogen fixation were unaffected, at least under laboratory conditions.
  
  
  CONCLUSIONS
  Although no yield penalty has been reported for moderate elevated seed stearic acid content in soybean seeds, our results demonstrate that genetic alteration of seed traits can have unforeseen pleiotropic consequences. We have identified a role for fatty acid biosynthesis, and SACPD activity in particular, in the establishment and maintenance of symbiotic nitrogen fixation.
authors.affiliation: USDA-ARS, University of Missouri-Columbia, 205 Curtis Hall, Columbia MO 65211, USA. Jason.Gillman@ars.usda.gov.
authors.forename: Jason D
authors.initials: JD
authors.lastname: Gillman
authors.forename: Minviluz G
authors.initials: MG
authors.lastname: Stacey
authors.forename: Yaya
authors.initials: Y
authors.lastname: Cui
authors.forename: Howard R
authors.initials: HR
authors.lastname: Berg
authors.forename: Gary
authors.initials: G
authors.lastname: Stacey
mesh_terms: D000595:Amino Acid Sequence; D020090:Chromosome Segregation; D032461:Chromosomes, Plant / Q000235:genetics; D055028:Comparative Genomic Hybridization; D003433:Crosses, Genetic; D005020:Ethyl Methanesulfonate; D005227:Fatty Acids / Q000378:metabolism*; D017353:Gene Deletion; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D056426:Genetic Loci; D008969:Molecular Sequence Data; D033363:Neutron Diffraction; D009586:Nitrogen Fixation; D010641:Phenotype; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D053204:Root Nodules, Plant / Q000033:anatomy & histology* / Q000378:metabolism; D012639:Seeds / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D013024:Soybean Oil; D013025:Glycine max / Q000235:genetics; D013229:Stearic Acids / Q000378:metabolism*
chemical_list: D005227:Fatty Acids; D010940:Plant Proteins; D013229:Stearic Acids; C031183:stearic acid; D013024:Soybean Oil; D005020:Ethyl Methanesulfonate