Department of Agricultural Biotechnology, National Academy of Agricultural Science, RDA, Suwon 441-707, Republic of Korea.
Gene. 2012 Nov 10;509(2):189-94. doi: 10.1016/j.gene.2012.08.032. Epub 2012 Aug 30.
The synthesis of polyunsaturated fatty acids (PUFAs), the most abundant fatty acids in plants, begins with a reaction catalyzed by fatty acid desaturase 2 (FAD2; EC 1.3.1.35), also called microsomal oleate Δ12-desaturase. Since the FAD2 gene was first identified in Arabidopsis thaliana, FAD2 research has gained wide interest as the essential enzyme for synthesizing PUFA. Grapes are one of the most frequently cultivated fruits in the world, with most commercial growers cultivating Vitis vinifera and V. labrusca. Grapeseed oil contains a high proportion, 60-70% of linoleic acid (18:2). We cloned two putative FAD2 genes from V. labrusca cv. Campbell Early based on V. vinifera genome sequences. Deduced amino acid sequences of two putative genes showed that VlFAD2s show high similarity to Arabidopsis FAD2 and commonly contain six transmembrane domain, three histidine boxes and endoplasmic reticulum (ER) retrieval motif representing the characteristics of fatty acid desaturase. Phylogenetic analyses of various plant FAD2s showed that VlFAD2-1 and VlFAD2-2 are separately grouped with constitutive and seed-type FAD2s, respectively. Southern blot showed that one or two bands are found in each lane. Because Campbell Early is a hybrid cultivar, FAD2-1 and FAD2-2 genes may exist as one copy in V. labrusca. Expression analysis in different tissues indicated that VlFAD2-1 is a constitutive gene but VlFAD2-2 is a seed-type gene. Complementation experiments of fad2-1 mutant Arabidopsis with VlFAD2-1 or VlFAD2-2 demonstrated that VlFAD2-1 and VlFAD2-2 can restore low PUFA proportion of fad2 to normal PUFA proportion.
多不饱和脂肪酸（PUFAs）是植物中含量最丰富的脂肪酸，其合成始于脂肪酸去饱和酶 2（FAD2；EC 1.3.1.35）催化的反应，也称为微粒体油酰 Δ12-去饱和酶。自从 FAD2 基因首次在拟南芥中被鉴定出来以来，作为合成 PUFA 的必需酶，FAD2 的研究引起了广泛的关注。葡萄是世界上最常种植的水果之一，大多数商业种植者种植的是酿酒葡萄（Vitis vinifera）和美洲种葡萄（V. labrusca）。葡萄籽油含有高比例的亚油酸（18:2），约 60-70%。我们根据酿酒葡萄基因组序列，从 V. labrusca cv. Campbell Early 克隆了两个假定的 FAD2 基因。两个假定基因的推导氨基酸序列表明，VlFAD2 与拟南芥 FAD2 高度相似，通常包含六个跨膜结构域、三个组氨酸盒和内质网（ER）回收基序，代表脂肪酸去饱和酶的特征。对各种植物 FAD2 的系统发育分析表明，VlFAD2-1 和 VlFAD2-2 分别与组成型和种子型 FAD2 分组。Southern blot 显示每个泳道中发现一个或两个条带。由于 Campbell Early 是一个杂交品种，FAD2-1 和 FAD2-2 基因可能在 V. labrusca 中存在一个拷贝。在不同组织中的表达分析表明，VlFAD2-1 是一个组成型基因，但 VlFAD2-2 是一个种子型基因。用 VlFAD2-1 或 VlFAD2-2 对 fad2-1 突变型拟南芥进行互补实验表明，VlFAD2-1 和 VlFAD2-2 可以将 fad2 的低 PUFA 比例恢复为正常的 PUFA 比例。
