title: A truncated FatB resulting from a single nucleotide insertion is responsible for reducing saturated fatty acids in maize seed oil.
abstract: We identified a G-nucleotide insertion in a maize FatB responsible for reducing saturated fatty acids through QTL mapping and map-based cloning and developed an allele-specific DNA marker for molecular breeding. Vegetable oils with reduced saturated fatty acids have signficant health benefits. SRS72NE, a Dow AgroSciences proprietory maize inbred line, was found to contain signficantly reduced levels of palmitic acid and total saturated fatty acids in seed oil when compared to other common inbreds. Using F2 and F3 populations derived from a cross between SRS72NE and a normal inbred SLN74, we have demonstrated that the reduced saturated fatty acid phenotype in SRS72NE is controlled by a single QTL on chromosome 9 that explains 79.1 % of palmitic acid and 79.6 % total saturated fatty acid variations. The QTL was mapped to an interval of 105 kb that contains one single gene, a type B fatty acyl-ACP thioesterase (ZmFatB; GRMZM5G829544). ZmFatB alleles from SRS72NE and common inbreds were cloned and sequenced. SRS72NE fatb allele contains a single nucleotide (G) insertion in the 6th exon, which creates a premature stop codon 22 base pairs down stream. As a result, ZmFatB protein from SRS72NE is predicted to contain eight altered and 90 deleted amino acids at its C-terminus. Because the affected region is part of the conserved acyl-ACP thioesterase catalytic domain, the truncated ZmFatB in SRS72NE is likely non-functional. We also show that fatb RNA level in SRS72NE is reduced by 4.4-fold when compared to the normal allele SNL74. A high throughput DNA assay capable of differentiating the normal and reduced saturate fatty acid alleles has been developed and can be used for accelerated molecular breeding.
authors.affiliation: Dow AgroSciences LLC, 9330 Zionsville Road, Indianapolis, IN, 46268, USA, pzheng@dow.com.
authors.forename: Peizhong
authors.initials: P
authors.lastname: Zheng
authors.forename: M D Ali
authors.initials: MD
authors.lastname: Babar
authors.forename: Seshasai
authors.initials: S
authors.lastname: Parthasarathy
authors.forename: Ryan
authors.initials: R
authors.lastname: Gibson
authors.forename: Kelly
authors.initials: K
authors.lastname: Parliament
authors.forename: Josh
authors.initials: J
authors.lastname: Flook
authors.forename: Thomas
authors.initials: T
authors.lastname: Patterson
authors.forename: Peter
authors.initials: P
authors.lastname: Friedemann
authors.forename: Siva
authors.initials: S
authors.lastname: Kumpatla
authors.forename: Steve
authors.initials: S
authors.lastname: Thompson
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D001947:Breeding; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D003314:Corn Oil / Q000737:chemistry* / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D005227:Fatty Acids / Q000032:analysis*; D018506:Gene Expression Regulation, Plant; D005838:Genotype; D008969:Molecular Sequence Data; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D040641:Quantitative Trait Loci; D012639:Seeds / Q000737:chemistry* / Q000235:genetics; D017422:Sequence Analysis, DNA; D013869:Thiolester Hydrolases / Q000032:analysis; D003313:Zea mays / Q000737:chemistry / Q000235:genetics*
chemical_list: D018744:DNA, Plant; D005227:Fatty Acids; D010940:Plant Proteins; D003314:Corn Oil; D013869:Thiolester Hydrolases; C018748:oleoyl-(acyl-carrier-protein) hydrolase