Hernández M Luisa, Sicardo M Dolores, Martínez-Rivas José M
Department of Biochemistry and Molecular Biology of Plant Products, Instituto de la Grasa (IG-CSIC), Campus Universidad Pablo de Olavide, 41013 Sevilla, Spain.
Department of Biochemistry and Molecular Biology of Plant Products, Instituto de la Grasa (IG-CSIC), Campus Universidad Pablo de Olavide, 41013 Sevilla, Spain
Plant Cell Physiol. 2016 Jan;57(1):138-51. doi: 10.1093/pcp/pcv159. Epub 2015 Oct 29.
Linolenic acid is a polyunsaturated fatty acid present in plant lipids, which plays key roles in plant metabolism as a structural component of storage and membrane lipids, and as a precursor of signaling molecules. The synthesis of linolenic acid is catalyzed by two different ω-3 fatty acid desaturases, which correspond to microsomal- (FAD3) and chloroplast- (FAD7 and FAD8) localized enzymes. We have investigated the specific contribution of each enzyme to the linolenic acid content in olive fruit. With that aim, we isolated two different cDNA clones encoding two ω-3 fatty acid desaturases from olive (Olea europaea cv. Picual). Sequence analysis indicates that they code for microsomal (OepFAD3B) and chloroplast (OepFAD7-2) ω-3 fatty acid desaturase enzymes, different from the previously characterized OekFAD3A and OekFAD7-1 genes. Functional expression in yeast of the corresponding OepFAD3A and OepFAD3B cDNAs confirmed that they encode microsomal ω-3 fatty acid desaturases. The linolenic acid content and transcript levels of olive FAD3 and FAD7 genes were measured in different tissues of Picual and Arbequina cultivars, including mesocarp and seed during development and ripening of olive fruit. Gene expression and lipid analysis indicate that FAD3A is the gene mainly responsible for the linolenic acid present in the seed, while FAD7-1 and FAD7-2 contribute mostly to the linolenic acid present in the mesocarp and, therefore, in the olive oil. These results also indicate the relevance of lipid trafficking between the endoplasmic reticulum and chloroplast in determining the linolenic acid content of membrane and storage lipids in oil-accumulating photosynthetic tissues.
亚麻酸是一种存在于植物脂质中的多不饱和脂肪酸，作为储存脂质和膜脂的结构成分以及信号分子的前体，在植物代谢中发挥着关键作用。亚麻酸的合成由两种不同的ω-3脂肪酸去饱和酶催化，这两种酶分别对应于定位于微粒体的（FAD3）和叶绿体的（FAD7和FAD8）酶。我们研究了每种酶对橄榄果实中亚麻酸含量的具体贡献。为此，我们从橄榄（油橄榄品种皮夸尔）中分离出两个不同的编码两种ω-3脂肪酸去饱和酶的cDNA克隆。序列分析表明，它们编码微粒体（OepFAD3B）和叶绿体（OepFAD7-2）ω-3脂肪酸去饱和酶，与先前鉴定的OekFAD3A和OekFAD7-1基因不同。相应的OepFAD3A和OepFAD3B cDNA在酵母中的功能表达证实它们编码微粒体ω-3脂肪酸去饱和酶。在皮夸尔和阿贝基纳品种的不同组织中，包括橄榄果实发育和成熟期间的中果皮和种子，测量了橄榄FAD3和FAD7基因的亚麻酸含量和转录水平。基因表达和脂质分析表明，FAD3A是种子中亚麻酸的主要负责基因，而FAD7-1和FAD7-2主要促成中果皮以及因此橄榄油中的亚麻酸。这些结果还表明，内质网和叶绿体之间的脂质转运在决定油积累光合组织中膜脂和储存脂质的亚麻酸含量方面具有重要意义。
