Christie P J, Ward J E, Winans S C, Nester E W
Department of Microbiology, University of Washington, Seattle 98195.
J Bacteriol. 1988 Jun;170(6):2659-67. doi: 10.1128/jb.170.6.2659-2667.1988.
Agrobacterium tumefaciens transfers T-DNA into the plant genome by a process mediated by Ti plasmid-encoded vir genes. Cleavage at T-DNA border sequences by the VirD endonuclease generates linear, single-stranded T-DNA molecules. In the work described in this report, we used electrophoretic mobility shift assays to show that the purified virE2 gene product binds to single-stranded DNA. VirE2 protein associates with T-DNA as shown by immunoprecipitation studies with VirE2-specific antiserum. The VirE2 protein was detected primarily in the cytoplasm, but also in the inner and outer membrane and periplasmic fractions. Virulence of a virE2 mutant was restored by mixed infection with strains carrying an intact vir region, but not with virA, virB, virD, virE, or virG mutants or chvA, chvB, or exoC mutants. We propose that the VirE2 protein is involved in the processing of T-DNA and in T-strand protection during transfer to the plant cell.
根癌土壤杆菌通过由Ti质粒编码的vir基因介导的过程将T-DNA转移到植物基因组中。VirD核酸内切酶在T-DNA边界序列处切割产生线性单链T-DNA分子。在本报告所述的工作中，我们使用电泳迁移率变动分析表明纯化的virE2基因产物与单链DNA结合。用VirE2特异性抗血清进行免疫沉淀研究表明，VirE2蛋白与T-DNA相关联。主要在细胞质中检测到VirE2蛋白，但在内膜、外膜和周质组分中也有检测到。通过与携带完整vir区域的菌株混合感染可恢复virE2突变体的毒力，但与virA、virB、virD、virE或virG突变体或chvA、chvB或exoC突变体混合感染则不能恢复。我们提出，VirE2蛋白参与T-DNA的加工以及在转移到植物细胞过程中对T链的保护。
