United States Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, 1100 Allen Toussaint Blvd, New Orleans, LA, 70124, USA.
BMC Plant Biol. 2023 Mar 17;23(1):147. doi: 10.1186/s12870-023-04160-8.
Cotton (Gossypium sp.) has been cultivated for centuries for its spinnable fibers, but its seed oil also possesses untapped economic potential if, improvements could be made to its oleic acid content.
Previous studies, including those from our laboratory, identified pima accessions containing approximately doubled levels of seed oil oleic acid, compared to standard upland cottonseed oil. Here, the molecular properties of a fatty acid desaturase encoded by a mutant allele identified by genome sequencing in an earlier analysis were analyzed. The mutant sequence is predicted to encode a C-terminally truncated protein lacking nine residues, including a predicted endoplasmic reticulum membrane retrieval motif. We determined that the mutation was caused by a relatively recent movement of a Ty1/copia type retrotransposon that is not found associated with this desaturase gene in other sequenced cotton genomes. The mutant desaturase, along with its repaired isozyme and the wild-type A-subgenome homoeologous protein were expressed in transgenic yeast and stably transformed Arabidopsis plants. All full-length enzymes efficiently converted oleic acid to linoleic acid. The mutant desaturase protein produced only trace amounts of linoleic acid, and only when strongly overexpressed in yeast cells, indicating that the missing C-terminal amino acid residues are not strictly required for enzyme activity, yet are necessary for proper subcellular targeting to the endoplasmic reticulum membrane.
These results provide the biochemical underpinning that links a genetic lesion present in a limited group of South American pima cotton accessions and their rare seed oil oleic acid traits. Markers developed to the mutant desaturase allele are currently being used in breeding programs designed to introduce this trait into agronomic upland cotton varieties.
棉花(Gossypium sp.)已经被种植了几个世纪,因为它的可纺纤维,但如果可以提高其油酸含量,其籽油也具有未开发的经济潜力。
之前的研究,包括我们实验室的研究,确定了比标准陆地棉籽油含有大约两倍种子油油酸的比马棉品种。在这里,对早期分析中通过基因组测序鉴定的突变等位基因编码的脂肪酸去饱和酶的分子特性进行了分析。突变序列预测编码一种 C 端截短的蛋白质,缺失九个残基,包括一个预测的内质网膜回收基序。我们确定该突变是由 Ty1/copia 型逆转录转座子的相对近期移动引起的,该转座子在其他测序棉基因组中未与该去饱和酶基因相关联。突变去饱和酶及其修复同工酶和野生型 A 亚基因组同源蛋白在转基因酵母和稳定转化的拟南芥植物中表达。所有全长酶都有效地将油酸转化为亚油酸。突变去饱和酶蛋白仅产生痕量的亚油酸,并且仅在酵母细胞中强烈过表达时才产生,这表明缺失的 C 末端氨基酸残基不是酶活性所必需的,但对于正确的内质网膜亚细胞靶向是必要的。
这些结果提供了生化基础,将存在于有限数量的南美比马棉品种及其罕见的种子油油酸性状中的遗传缺陷与该性状联系起来。目前正在使用针对突变去饱和酶等位基因的标记物来设计引入该性状到农业旱地棉品种的育种计划。