一个可介导链霉菌PKS基因向植物转化的杂合质粒的构建

A Construct for the Trial Expression of Streptomyces PKS Gene in Plant

抗生素FR-008是由链霉菌FR-008所产生的一种七烯大环内酯类抗真菌抗生素。胡志浩等已克隆了长达约105kb的FR-008聚酮合酶(PKS)基因簇,对该基因簇中相邻于pabAB基因下游的3.8kbDNA进行序列分析,找到一个多功能聚酮合酶基因的起点,与数据库中蛋白质序列的比较分析揭示出一个尚未结束的大型开读框架的存在,它与抗细菌大环内酯类抗生素-红霉素生物合成所需的Ⅰ型聚酮合酶(PKS)基因中的乙酰转移酶(AT)和β-酮酰合酶(KS)的功能结构域显示出了高度的同源性,从分子水平上证实了FR-008抗生素由Ⅰ型PKS所合成。本实验将3.8kb中的编码聚酮合酶的部分开读框架通过基因工程的方法插入植物表达载体WRG2410上,从而成功构建了表达性质粒pHZ321。

3. 8kb DNA immediately downstream of pabAB genes was sequenced and it was confirmed that the FR-008 antibiotic was synthesiecl by Type 1 PKS. We were interested to see whether the FR-008 PKS genes can be expressed in plant. The sequence information was thus used to make a construct for gene expression in plant. Plasmid WRG2410 containing 35S promoter was chosen as a vector to construct pHZ321 which is now ready for introdction into plant. At this stage, we neither expect the introduced construct in plant to produce a functional enzyme, nor tc confer fungal resistance to plant, but it will give some indication whether the Streptomyces PKS gene, which has an extremely high G+C content (76%) can be expressed in various plants.