Bundock P, den Dulk-Ras A, Beijersbergen A, Hooykaas P J
Institute of Molecular Plant Sciences, Clusius Laboratory, Leiden University, The Netherlands.
EMBO J. 1995 Jul 3;14(13):3206-14. doi: 10.1002/j.1460-2075.1995.tb07323.x.
Agrobacterium tumefaciens transfers part of its tumour-inducing (Ti) plasmid, the transferred or T-DNA, to plants during tumourigenesis. This represents the only example of naturally occurring trans-kingdom transfer of genetic material. Here we report that A.tumefaciens can transfer its T-DNA not only to plant cells, but also to another eukaryote, namely the yeast Saccharomyces cerevisiae. The Ti plasmid virulence (vir) genes that mediate T-DNA transfer to plants were found to be essential for transfer to yeast as well. Transgenic S.cerevisiae strains were analysed for their T-DNA content. Results showed that T-DNA circles were formed in yeast with precise fusions between the left and right borders. Such T-DNA circles were stably maintained by the yeast if the replicator from the yeast 2 mu plasmid was present in the T-DNA. Integration of T-DNA in the S.cerevisiae genome was found to occur via homologous recombination. This contrasts with integration in the plant genome, where T-DNA integrates preferentially via illegitimate recombination. Our results thus suggest that the process of T-DNA integration is predominantly determined by host factors.
根癌土壤杆菌在致瘤过程中将其部分致瘤（Ti）质粒，即转移DNA（T-DNA）转移至植物中。这是天然发生的跨界遗传物质转移的唯一实例。在此我们报告，根癌土壤杆菌不仅能将其T-DNA转移至植物细胞，还能转移至另一种真核生物，即酿酒酵母。发现介导T-DNA向植物转移的Ti质粒毒性（vir）基因对于向酵母的转移同样至关重要。对转基因酿酒酵母菌株的T-DNA含量进行了分析。结果显示，T-DNA在酵母中形成环状，其左右边界之间实现了精确融合。如果T-DNA中存在来自酵母2μm质粒的复制子，此类T-DNA环就能在酵母中稳定维持。发现T-DNA通过同源重组整合到酿酒酵母基因组中。这与在植物基因组中的整合情况形成对比，在植物基因组中T-DNA优先通过非同源重组进行整合。因此，我们的结果表明，T-DNA整合过程主要由宿主因子决定。
