Sinkar V P, White F F, Furner I J, Abrahamsen M, Pythoud F, Gordon M P
Department of Biochemistry, University of Washington, Seattle, Washington 98195.
Plant Physiol. 1988 Feb;86(2):584-90. doi: 10.1104/pp.86.2.584.
Transgenic plants harboring the left transfer DNA (T(L)-DNA) of the root inducing plasmid of Agrobacterium rhizogenes show many developmental abnormalities. We observed frequent appearance of normal looking lateral (revertant) shoots from such aberrant plants. Unlike aberrant shoots of the plant, revertant shoots exhibited a very high growth rate and set viable seeds. Sexual and vegetative reproduction studies showed inheritance of the revertant phenotype. Southern hybridization experiments demonstrated that the T-DNA pattern was identical in aberrant and revertant shoots, indicating that the revertant phenotype was not due to deletion or rearrangement of the T-DNA genes. Specific T-DNA transcripts were not expressed in revertant shoots. Thus, the revertant phenotype appears to result from the transcriptional inactivation of T-DNA genes. We propose that similar events in the past may have mediated horizontal acquisition of T(L)-DNA genes by ancestors of the genus Nicotiana, which are still found as silent endogenous T-DNA in present day untransformed Nicotiana species.
携带发根农杆菌根诱导质粒左转移DNA（T（L）-DNA）的转基因植物表现出许多发育异常。我们观察到，这类异常植物频繁出现外观正常的侧枝（回复枝）。与植物的异常枝条不同，回复枝生长速度非常快，并能结出可育种子。有性和无性繁殖研究表明，回复表型具有遗传性。Southern杂交实验表明，异常枝条和回复枝条中的T-DNA模式相同，这表明回复表型并非由于T-DNA基因的缺失或重排所致。回复枝条中未表达特定的T-DNA转录本。因此，回复表型似乎是由T-DNA基因的转录失活导致的。我们推测，过去类似的事件可能介导了烟草属祖先对T（L）-DNA基因的水平获得，如今在未转化的烟草物种中仍可发现这些作为沉默内源T-DNA的基因。
