Department of Plant Science, University of Manitoba, 66 Dafoe Rd, Winnipeg, MB, R3T 2N2, Canada.
Theor Appl Genet. 2013 Oct;126(10):2627-41. doi: 10.1007/s00122-013-2161-2. Epub 2013 Aug 9.
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.
亚麻（Linum usitatissimum L.）是ω-3 脂肪酸的最丰富植物来源之一，其健康益处备受赞誉。在这项研究中，通过对 120 个亚麻品种（包括一些 EMS 突变体系）的 6 个同源基因进行测序，确定了编码硬脂酰-ACP 去饱和酶（SAD）、脂肪酸去饱和酶 2（FAD2）和 3（FAD3）的基因的遗传变异程度。总共鉴定出 sad1 和 sad2 的 6 个等位基因、fad2a 的 21 个、fad2b 的 5 个、fad3a 的 15 个和 fad3b 的 18 个。等位基因预测的氨基酸序列分别预测了 4、2、3、4、6 和 7 种同工型。基因之间的等位基因频率差异很大。fad3a 有 110 个 SNP 和 19 个插入缺失，fad3b 有 50 个 SNP 和 5 个插入缺失，表现出最高水平的遗传变异。虽然大多数 SNP 和所有插入缺失都是沉默突变，但这两个基因都携带无意义 SNP 突变，导致过早的终止密码子，这在 sad 和 fad2 基因中没有观察到。在诱导突变体系中发现的一些等位基因和同工型在自然种质中不存在。将这些基因型数据与 120 个亚麻品种在六个田间试验中表型的脂肪酸组成数据进行相关性分析，发现一些 SAD 和 FAD 同工型对脂肪酸组成、油含量和碘值有统计学显著影响。鉴定出的六种去饱和酶的新等位基因变异体和同工型将成为开发具有独特和有用脂肪酸图谱的油用亚麻的资源。
