Dohmen R J, Strasser A W, Zitomer R S, Hollenberg C P
Institut für Mikrobiologie, Heinrich-Heine-Universität Düsseldorf, Federal Republic of Germany.
Curr Genet. 1989 May;15(5):319-25. doi: 10.1007/BF00419911.
High frequency transformation of a Schwanniomyces occidentalis mutant defective in the last step of tryptophan synthesis was achieved with plasmids containing the tryptophan synthetase gene (TRP5) of Saccharomyces cerevisiae and an autonomous replication sequence from S. occidentalis, which we called "SwARS1". The SwARS1 fragment is also functional in S. cerevisiae. The average copy number of the plasmids in both yeast species was 5-10 per cell under selective conditions. S. occidentalis cells that were transformed with an autonomously replicating plasmid carrying the cloned alpha-amylase gene from S. occidentalis secreted about five times more alpha-amylase than cells without additional copies of the alpha-amylase gene. Both the chromosomal copy and the plasmid-carried copies of the alpha-amylase gene were repressed in the presence of glucose. This transformation system provides a possibility to improve starch degradation by S. occidentalis.
利用含有酿酒酵母色氨酸合成酶基因（TRP5）和西方许旺酵母自主复制序列（我们称之为“SwARS1”）的质粒，实现了对在色氨酸合成最后一步存在缺陷的西方许旺酵母突变体的高频转化。SwARS1片段在酿酒酵母中也具有功能。在选择条件下，两种酵母细胞中质粒的平均拷贝数均为每个细胞5 - 10个。用携带从西方许旺酵母克隆的α - 淀粉酶基因的自主复制质粒转化的西方许旺酵母细胞，分泌的α - 淀粉酶比没有额外α - 淀粉酶基因拷贝的细胞多约五倍。在葡萄糖存在的情况下，α - 淀粉酶基因的染色体拷贝和质粒携带的拷贝均受到抑制。该转化系统为提高西方许旺酵母对淀粉的降解能力提供了一种可能性。
