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Genetic variation of six desaturase genes in flax and their impact on fatty acid composition.

ABSTRACT: Flax (Linum usitatissimum L.) is one of the richest plant sources of omega-3 fatty acids praised for their health benefits. In this study, the extent of the genetic variability of genes encoding stearoyl-ACP desaturase (SAD), and fatty acid desaturase 2 (FAD2) and 3 (FAD3) was determined by sequencing the six paralogous genes from 120 flax accessions representing a broad range of germplasm including some EMS mutant lines. A total of 6 alleles for sad1 and sad2, 21 for fad2a, 5 for fad2b, 15 for fad3a and 18 for fad3b were identified. Deduced amino acid sequences of the alleles predicted 4, 2, 3, 4, 6 and 7 isoforms, respectively. Allele frequencies varied greatly across genes. Fad3a, with 110 SNPs and 19 indels, and fad3b, with 50 SNPs and 5 indels, showed the highest levels of genetic variations. While most of the SNPs and all the indels were silent mutations, both genes carried nonsense SNP mutations resulting in premature stop codons, a feature not observed in sad and fad2 genes. Some alleles and isoforms discovered in induced mutant lines were absent in the natural germplasm. Correlation of these genotypic data with fatty acid composition data of 120 flax accessions phenotyped in six field experiments revealed statistically significant effects of some of the SAD and FAD isoforms on fatty acid composition, oil content and iodine value. The novel allelic variants and isoforms identified for the six desaturases will be a resource for the development of oilseed flax with unique and useful fatty acid profiles.

SUBMITTER: Thambugala D

PROVIDER: S-EPMC3782649 | biostudies-literature | 2013 Oct

REPOSITORIES: biostudies-literature

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Genetic variation of six desaturase genes in flax and their impact on fatty acid composition.

Thambugala Dinushika D Duguid Scott S Loewen Evelyn E Rowland Gordon G Booker Helen H You Frank M FM Cloutier Sylvie S

TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik 20130809 10

Flax (Linum usitatissimum L.) is one of the richest plant sources of omega-3 fatty acids praised for their health benefits. In this study, the extent of the genetic variability of genes encoding stearoyl-ACP desaturase (SAD), and fatty acid desaturase 2 (FAD2) and 3 (FAD3) was determined by sequencing the six paralogous genes from 120 flax accessions representing a broad range of germplasm including some EMS mutant lines. A total of 6 alleles for sad1 and sad2, 21 for fad2a, 5 for fad2b, 15 for ...[more]

PMID: 23928861

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Project description:BackgroundFlax (Linum usitatissimum L.) is grown for fiber and seed in many countries. Flax cultivars differ in the oil composition and, depending on the ratio of fatty acids, are used in pharmaceutical, food, or paint industries. It is known that genes of SAD (stearoyl-ACP desaturase) and FAD (fatty acid desaturase) families play a key role in the synthesis of fatty acids, and some alleles of these genes are associated with a certain composition of flax oil. However, data on genetic polymorphism of these genes are still insufficient.ResultsOn the basis of the collection of the Institute for Flax (Torzhok, Russia), we formed a representative set of 84 cultivars and lines reflecting the diversity of fatty acid composition of flax oil. An approach for the determination of full-length sequences of SAD1, SAD2, FAD2A, FAD2B, FAD3A, and FAD3B genes using the Illumina platform was developed and deep sequencing of the 6 genes in 84 flax samples was performed on MiSeq. The obtained high coverage (about 400x on average) enabled accurate assessment of polymorphisms in SAD1, SAD2, FAD2A, FAD2B, FAD3A, and FAD3B genes and evaluation of cultivar/line heterogeneity. The highest level of genetic diversity was observed for FAD3A and FAD3B genes - 91 and 62 polymorphisms respectively. Correlation analysis revealed associations between particular variants in SAD and FAD genes and predominantly those fatty acids whose conversion they catalyze: SAD - stearic and oleic acids, FAD2 - oleic and linoleic acids, FAD3 - linoleic and linolenic acids. All except one low-linolenic flax cultivars/lines contained both the substitution of tryptophan to stop codon in the FAD3A gene and histidine to tyrosine substitution in the FAD3B gene, while samples with only one of these polymorphisms had medium content of linolenic acid and cultivars/lines without them were high-linolenic.ConclusionsGenetic polymorphism of SAD and FAD genes was evaluated in the collection of flax cultivars and lines with diverse oil composition, and associations between particular polymorphisms and the ratio of fatty acids were revealed. The achieved results are the basis for the development of marker-assisted selection and DNA-based certification of flax cultivars.

Dataset Information

Genetic variation of six desaturase genes in flax and their impact on fatty acid composition.

Publications

Genetic variation of six desaturase genes in flax and their impact on fatty acid composition.

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