title: A knockout mutation in the lignin biosynthesis gene CCR1 explains a major QTL for acid detergent lignin content in Brassica napus seeds.
abstract: Seed coat phenolic compounds represent important antinutritive fibre components that cause a considerable reduction in value of seed meals from oilseed rape (Brassica napus). The nutritionally most important fibre compound is acid detergent lignin (ADL), to which a significant contribution is made by phenylpropanoid-derived lignin precursors. In this study, we used bulked-segregant analysis in a population of recombinant inbred lines (RILs) from a cross of the Chinese oilseed rape lines GH06 (yellow seed, low ADL) and P174 (black seed, high ADL) to identify markers with tight linkage to a major quantitative trait locus (QTL) for seed ADL content. Fine mapping of the QTL was performed in a backcross population comprising 872 BC(1)F(2) plants from a cross of an F(7) RIL from the above-mentioned population, which was heterozygous for this major QTL and P174. A 3:1 phenotypic segregation for seed ADL content indicated that a single, dominant, major locus causes a substantial reduction in ADL. This locus was successively narrowed to 0.75 cM using in silico markers derived from a homologous Brassica rapa sequence contig spanning the QTL. Subsequently, we located a B. rapa orthologue of the key lignin biosynthesis gene CINNAMOYL CO-A REDUCTASE 1 (CCR1) only 600 kbp (0.75 cM) upstream of the nearest linked marker. Sequencing of PCR amplicons, covering the full-length coding sequences of Bna.CCR1 homologues, revealed a locus in P174 whose sequence corresponds to the Brassica oleracea wild-type allele from chromosome C8. In GH06, however, this allele is replaced by a homologue derived from chromosome A9 that contains a loss-of-function frameshift mutation in exon 1. Genetic and physical map data infer that this loss-of-function allele has replaced a functional Bna.CCR1 locus on chromosome C8 in GH06 by homoeologous non-reciprocal translocation.
authors.affiliation: Department of Plant Breeding, IFZ Research Centre for Biosystems, Land Use and Nutrition, Justus Liebig University, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany.
authors.forename: Liezhao
authors.initials: L
authors.lastname: Liu
authors.forename: Anna
authors.initials: A
authors.lastname: Stein
authors.forename: Benjamin
authors.initials: B
authors.lastname: Wittkop
authors.forename: Pouya
authors.initials: P
authors.lastname: Sarvari
authors.forename: Jiana
authors.initials: J
authors.lastname: Li
authors.forename: Xingying
authors.initials: X
authors.lastname: Yan
authors.forename: Felix
authors.initials: F
authors.lastname: Dreyer
authors.forename: Martin
authors.initials: M
authors.lastname: Frauen
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Friedt
authors.forename: Rod J
authors.initials: RJ
authors.lastname: Snowdon
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000235:genetics*; D000483:Alleles; D017360:Arabidopsis / Q000235:genetics; D029688:Brassica napus / Q000235:genetics*; D002482:Cellulose / Q000737:chemistry; D002874:Chromosome Mapping; D003433:Crosses, Genetic; D003902:Detergents / Q000494:pharmacology; D005091:Exons; D016368:Frameshift Mutation; D005819:Genetic Markers; D006579:Heterozygote; D008031:Lignin / Q000378:metabolism; D008957:Models, Genetic; D009154:Mutation; D010641:Phenotype; D040641:Quantitative Trait Loci; D012639:Seeds / Q000378:metabolism
chemical_list: D003902:Detergents; D005819:Genetic Markers; D002482:Cellulose; D008031:Lignin; D000445:Aldehyde Oxidoreductases; C019904:cinnamoyl CoA reductase