杜氏盐藻异养表达载体的构建及异养转化株的鉴定

Construction of Dunaliella salina heterotrophic expression vectors and identification of heterotrophically transformed algal strains

分别构建杜氏盐藻诱导型和组成型异养表达载体,筛选并初步鉴定异养转化藻株。通过RT-PCR从人胎盘组织中克隆并鉴定人红细胞葡萄糖转运基因(Glut1),构建以诱导型双拷贝碳酸酐酶启动子(DCA)驱动Glut1表达的中间载体,然后与筛选标记Bar盒连接形成盐藻诱导型异养表达载体pMDDGN-Bar。此外,将pU?GUS(简称G5)质粒的GUS基因去除,回收大片段载体后与Glut1基因连接,构建以组成型启动子ubiquitin驱动的组成型异养表达载体G5Glut1-Bar。通过电击转化法转化盐藻,使Glut1得到表达,筛选具有草丁膦(PPT)抗性的表达Glut1的盐藻转化株。提取转化株总RNA,RT-PCR检测目的基因的整合。克隆获得了1479bp的Glut1序列,编码493个氨基酸。电泳检测各酶切结果表明Glut1、DCA、Nos和Bar盒已依次连接到相应的载体上,说明异养表达载体构建成功。经PPT筛选数周后,转化藻株生长良好,而对照野生藻株全部死亡。电泳检测RT-PCR产物表明两株转化株在相应位置(约250bp处)出现了较为特异的扩增条带,Blast同源性分析显示序列与人Glut1基因的同源性为100%。诱导型和组成型启动子驱动的盐藻异养表达载体构建成功,Glut1基因确已整合到盐藻的基因组中,构建的表达载体可用于盐藻中Glut1基因的表达。

We constructed inducible and constitutive heterotrophic expression vectors of Dunaliella salina （D. salina） and identified heterotrophic transformants. A gene encoding a glucose transporter （Glut1） was cloned from human placenta tissues by RT-PCR and sequenced. Inducible heterotrophic expression vector pMDDGN-Bar of D. salina, which included a duplicated carbonic anhydrase （DCA） promotor and a Bar selectable marker that could drive expression of the Glut1 gene in D. salina, was constructed by molecular biology methods. In addition, we constructed another vector G5Glut1-Bar that contained a constitutive ubiquitin promotor, Glut1 and Bar box. The two expression vectors were introduced into D. salina by electroporation method, and then screened the transformants with phosphinothricin （PPT）. Total RNA of the transformants extracted was used to analyze the integration of the target gene （Glut1） by RT-PCR. The cloned Glut1 sequence was 1479 bp and encoded 493 amino acids. The results of all enzymes digesting showed that two expression vectors were successfully constructed. After screening by PPT for several weeks, the transfomants grew well whereas wild-type cells died completely. The result of RT-PCR indicated that two transformants both had an about 250 bp specific band and the sequence homology was 100% compared with the human Glut1 sequence by Blast analysis. Taken altogether, inducible and constitutive heterotrophic expression vectors of D. salina was constructed successfully and the Glut1 gene was integrated into the genome of D. salina. Expression vectors above-mentioned may be used for the expression of the foreign Glut1 gene in D. salina.