Abstract
Seeds exhibit wide variation in the fatty acid composition of their storage oil. However, the genetic basis of this variation is only partially understood. Here we have used a multi-parent advanced generation inter-cross (MAGIC) population to study the genetic control of fatty acid chain length in Arabidopsis thaliana seed oil. We mapped four quantitative trait loci (QTL) for the quantity of the major very long chain fatty acid species 11-eicosenoic acid (20:1), using multiple QTL modelling. Surprisingly, the main-effect QTL does not coincide with FATTY ACID ELONGASE1 and a parallel genome wide association study suggested that LYSOPHOSPHATIDYLCHOLINE ACYLTRANSFERASE 2 (LPCAT2) is a candidate for this QTL. Regression analysis also suggested that LPCAT2 expression and 20:1 content in seeds of the 19 MAGIC founder accessions are related. LPCAT is a key component of the Lands cycle; an acyl editing pathway that enables acyl-exchange between the acyl-Coenzyme A and phosphatidylcholine precursor pools used for microsomal fatty acid elongation and desaturation, respectively. We Mendelianised the main-effect QTL using biparental chromosome segment substitution lines and carried out complementation tests to show that a single cis-acting polymorphism in the LPCAT2 promoter causes the variation in seed 20:1 content, by altering the LPCAT2 expression level and total LPCAT activity in developing siliques. Our work establishes that oilseed species exhibit natural variation in the enzymic capacity for acyl editing and this contributes to the genetic control of storage oil composition.
Highlights
IntroductionSeed maturation is associated with the deposition of storage reserves, such as oil (triacylglycerol), carbohydrates and proteins[1]
Seed maturation is associated with the deposition of storage reserves, such as oil, carbohydrates and proteins[1]
We show that natural variation in LPCAT231–33 is a determinant of seed storage oil composition in Arabidopsis
Summary
Seed maturation is associated with the deposition of storage reserves, such as oil (triacylglycerol), carbohydrates and proteins[1]. Several studies have used recombinant inbred populations derived from bi-parent crosses to map quantitative trait loci (QTL) controlling oil composition[6,14,15,16]. Previous studies have identified many genomic regions that are associated with seed TAG composition[6,14,16,18], only one QTL has ever been fine-mapped and the causal sequence variant determined[15]. Kover et al, (2009) created a large Arabidopsis MAGIC population that encompasses the genetic variation within 19 founder accessions and consists of >500 recombinant inbred lines (RILs)[24] Both the founder accessions and the RILs, have been sequenced providing comprehensive marker coverage, consisting of ~3 million individual sequence variants[25,26]. The aim of this study was to investigate the control of fatty acid elongation and to identify both QTL and their underlying causal sequence variants
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