Isolation of Fatty Acid Biosynthetic Genes from Arabidopsis - A First Step in Plant Oil Content Modification

油料作物的脂肪酸组成是一种重要的经济性状，可以通过基因工程进行改造。例如，设计一种亚麻酸含量较低的菜籽油是可能的，亚麻酸是一种会导致酸败的不受欢迎的成分。转座子标记提供了一种强大的遗传方法来分离编码难以纯化的酶的基因，例如那些参与FA生物合成的基因。小模式植物拟南芥是油菜籽的近亲。我们建议分离在拟南芥中负责亚麻酸形成的Fad3基因，作为改变油菜籽FA组成的第一步。我们将使用我们的工程化链霉素抗性试验(SPT)来直观地检测玉米转座子激活子(Ac)在拟南芥中的转座。在同样的实验中，体细胞切除SPT：：Ac基因的Ac会在链霉素萌发的幼苗的白色子叶上产生绿色斑点，而生发转座会产生绿色回复植株。因此，SPT：：AC系统允许我们选择经过转座的植物。通过从携带与Fad3紧密连锁的Ac的植物中选择绿色回复突变体，并对它们进行自交，我们应该能够识别标记的Fad3突变并通过与Ac的同源性来克隆它们。通过与拟南芥基因的同源性，可以从油菜中克隆出类似的基因，然后对其进行修改并重新引入油料作物。

The fatty acid (FA) composition of oilseed crops is an economically important trait amenable to modification by genetic engineering. For example, it should be possible to engineer a canola (rapeseed) oil with a lower content of linolenic acid, an undesirable component that causes rancidity. Transposon tagging provides a powerful genetic approach to isolate genes encoding enzymes that are difficult to purify, such as those involved in FA biosynthesis. The small model plant Arabidopsis thaliana is a close relative of rapeseed. We propose to isolate the fad3 gene, responsible for the formation of linolenic acid in Arabidopsis, as a first step towards the modification of the FA composition in canola. We will use our engineered streptomycin resistance assay (SPT) to visually detect transposition of the maize transposon Activator (Ac) in Arabidopsis. Somatic excision of Ac from an SPT::Ac gene produces green spots on the white cotyledons of seedlings germinated on streptomycin and germinal transposition results in green revertant seedlings in the same assay. Therefore, the SPT::Ac system allows us to select plants that have undergone transposition. By selecting green revertants from plants that carry Ac closely linked to fad3, and selfing them, we should be able to identify tagged fad3 mutations and clone them by homology to Ac. The analogous gene can be cloned from canola by homology to the Arabidopsis gene and subsequently modified and reintroduced to the oilseed crop.